The origin of ground reaction forces

Considerable confusion sometimes exists about the origin of the forces measured by a force platform. The best way to understand these is to think of the force platform as a whole-body accelerometer. Since Force = mass x acceleration (Newton's 2nd Law of Motion), any acceleration of the body will be reflected in a reaction when at least one foot is on the ground. An upwards acceleration (as occurs at push-off) will be reflected in an increase in the vertical load (weight) recorded, while a downwards acceleration (as occurs during mid-stance) will reduce the effective body weight. Note that a downwards deceleration (such as occurs at initial contact) is equivalent to an upwards acceleration, and vice versa.

It is clear from the above that the ground reaction forces reflect accelerations of the body's centre of mass. They are not, as many wrongly people believe, influenced by changes in footwear. This is illustrated in the following set of curves taken from a subject walking three times barefoot and shod, then walking like Groucho Marx (minimal vertical accelerations) and as if on the moon (large vertical accelerations).

It can be seen that there are no significant differences in the curves according to footwear, but considerable differences when trunk accelerations are modified.


Hello Kirtley,

I came across your theory of the "Origin of ground reaction forces" while
searching for somewhat similar data.
I am an engineer at Blue Giant.  We manufacture material handling equipment
used in factories and warehouses.  One of our products is a mechanical dock
leveler that bridges the gap between a tractor-trailer and the factory
floor.  The ramp is mechanically raised by the use of springs under the
dock.  A lip then extends to bridge the gap.  Personnel must walk up the
ramp in order to bring the lip down to the truck bed.  When doing this they
must overcome the strength of extension springs under the dock.

Sometimes a lighter person has trouble forcing the deck downwards because
they are not heavy enough.  They must walk further along the dock and
sometimes bounce downward to get it moving downward.  They should never be
jumping, but what they do is bend their knees quickly, producing a slight
acceleration of their upper body, and hence more force on the dock.  I am
having trouble determining the force somebody can produce by performing this
motion.  We have a scale that I have bounced on but the response time is not
good enough to get a proper reading of force.  Reading your reaction forces
article, it seems as though you might have or be able to direct me to, info
on producing a force greater than your body mass by quickly bending at the

You can call by phone or e-mail me.
Thank-you for your consideration.
Andy Erjavec

Blue Giant Limited
ext 291

Dr. Kirtley

I have been trying to interpret the GRF tracings during the stance phase of gait and have found
what appears to be conflicting information from the CGA website.

I will do my best to present this information as clearly and completely as possible.

In your "The origins of ground reaction forces" /faq/grfs.html, it states the following:
                An upwards acceleration (as occurs at push-off) will be reflected in an
increase in the vertical load (weight) recorded, while a downwards acceleration (as occurs
during mid-stance) will reduce the effective body weight.
I am not clear regarding the downward acceleration occurring at midstance, that would evidently
be the source of the reduced bodyweight and the midstance valley.

In an additional CGA posting, from Kinematic Definitions, it states and there is an
illustration that represents the fact that the COM actually moves upwards during midstance and
is higher in midstance than anywhere else during the normal gait cycle.  (

I seem to have difficulty trying to reason this out, (it probably should not be that
difficult), yet I continue to struggle.  Any information that would help me clear this up and
assist in my understanding of these GRF's would be greatly appreciated.  In addition, I have
looked for textbooks that explain the use and interpretation of force plates but have not been
satisfied with what I have found.  A few that I have looked through are Perry, Whittle,
Durward, and several general Biomechanics textbooks.  Are there any texts that you would

Thank you for your time in addressing these issues.

Kurt Neelly, PT

Dear Kurt,

No discrepancy - you're just getting mixed up between position and
acceleration. Displacement, velocity and accelerarion are always 90
degrees out of phase. Velocity is the slope of the displacement, and
acceleration the slope of the velocity. Think of it in stages (see
attached fig.):

1. When displacement is rising


2. When displacement is highest

to zero

3. When displacementis falling

4. When displacement is lowest

Does that help?



Bates, B., James, S.L. Osternig L.R., Sawhill, J and Hamill, J. (1982)
     Effects of running shoes on ground reaction forces. In Morecki &
     Fidelus (Eds) Biomechanics VII, University Park Press., Baltimore.

     Bergman , G., Kniggendorf, H., Graichen, F. and Rohlmann, A.
     (1995) Influence of shoes and heel strike on the loading of the hip
     joint. J. Biomechanics 28:817-827.

     Cavanagh, P. R. and Lafortune, M. A. (1980) Ground reaction forces
     in distance running. J. Biomech. 13, 397-406.

     Cavanagh, P.R. (1978) A technique for averaging centre of
     prepssure paths from a force platform. J. Biomech 11: 487-491.

     Cavanagh, P.R., Williams, K.R., and Clarke, T.E. (1981) A
     comparison of ground reaction forces during walking barefoot and in
     shoes. pp151-156 in Morecki et al (Eds) Biomechanics VII-B,
     University Park Press.

     Chu., M.L., Yasdani-Ardakani, S. Gradisar, I.A. & Askew, M.J.
     (1986) An in vivo simulation study of impulsive force transmission
     along the lower skeletal extremity. J. Biomech 19:979-987

     Clarke, T.E., Cooper, L.B. , Clark, D.E. & Hamill, C.L. (1985) The
     effect of increased running speed upon peak shank deceleration
     during ground contact. Pp 101-105 in. Winter et al (Eds)
     Biomechanics IX-B, Champaign, IL: Human Kinetics.

     Clarke, T. E., Frederick, E. C. and Cooper, L. B. (1983b) Effects of
     shoe cushioning upon ground reaction forces in running. Int. J.
     Sports Medicine 4:247-251.

     Cole, G.K., Nigg. B.M., Fick, G.H and Morlock, M. M. (1995) Internal loading of the foot and ankle during impact in running. J. Applied Biomechanics 11: 25-46.

     Dickinson, J.A., Cook, S.D. & Leinhardt T.M. (1985) The
     measurement of shock waves following heel strike during running J.
     Biomech 18: 415-422.

     Frederick, E.C. and Hagy J. L.(1986) Factors effecting peak vertical
     ground reaction forces in running. Int. J. Sports Biomech. 2: 41-49

     Hamill, J., Bates, B.T., Knutzen, K.M. and Sawhill, J.A. (1983)
     Variations in ground reaction force parameters at different running
     speeds. Human Movement Science, 2: 47- 56.

     Hamill, J., Bates, B.T., & Knutzen, K.M. (1984) Ground reaction
     force symmetry during walking and running. Research Quarterly,

     Falsetti, H.L., Burke, E.R. Feld, R.D., Frederick, E.C. and Ratering,
     C. (1983) Hematological variations after endurance running with hard
     and soft-soled shoes. Physician and Sportsmedicine 11(8):118-127

     Hennig, E.M. & Lafortune, M.A. (1988) Tibial bone and skin
     accelerations during running. In C.E. Cotton et al (Eds) Proc 5th
     Biennial Conf. And Human Locomotion Symposium of the Canadian
     Society of Biomechanics (pp 94-95) Ottowa: University of Ottowa,
     Dept. Kinanthropometry.

     Hennig, E.M. & Lafortune, M.A. (1991) Relationships between
     ground reaction force and tibial acceleration parameters. Int. J.
     Sports Biomech 7: 303-309.

     Lafortune, M.A. (1991) Three-dimensional acceleration of the tibia
     during walking and running. J. Biomechanics 24: 877-886.

     Lafortune, M.A., Lake, M.J. and Hennig, E.M. (1995) Transfer
     function between tibial acceleration and ground reaction force. J.
     Biomechanics 28:113-117.

     Lafortune, M.A. & Hennig, E.M. (1988) Effects of velocity and uphill
     slope on tibial shock during running. In C.E. Cotton et al (Eds) Proc
     5th Biennial Conf. And Human Locomotion Symposium of the
     Canadian Society of Biomechanics (pp 74-75) Ottowa: University of
     Ottowa, Dept. Kinanthropometry.

     Lafortune, M.A. & Hennig, E.M. (1989) Contribution of angular
     motion and gravity to tibial acceleration . In R.J. Gregor et al (Eds)
     Proc XII international Congress of Biomechanics. Los Angeles,
     UCLA, Dept of Kinesiology #334.

     Lafortune, M.A. & Hennig, E.M. (1992) Cushioning properties of
     footwear during walking: accelerometer and force platform
     measurements. Clinical Biomechanics 7: 181-184.

     Light, L.H., McLellan, G.E. and Klenerman, L. (1980) Skeletal
     transients on heel strike in normal walking with different footwear. J.
     Biomechanics 13: 477-480.

     Luethi, S.M., Nigg, B.M. and Bahlsen, H.A. (1984) The influence of
     varying shoe sole stiffnesses on impact forces in running. in Human
     Locomotion III, Proceedings of the 1984 Conference of the
     Canadian Society of Biomechanics.

     MacLellan, G.E. & Vyvyan, B. (1981) Management of pain beneath
     the heel and Achilles tendonitis with viscoelastic heel inserts.. Brit. J.
     Sports Medicine 15, 117-121.

     Ziegert , J.C. and Lewis, J.L (1979) The effect of soft tissues on
     measurements of vibrational bone motion by skin-mounted

     Frederick, E.C., Howley, E. T., Hamill, C.L. and Cooper. L.B. (1984) Ventilatory contributions to shock attenuation. Med. Sci. Sports. Ex. 16: 185.

     Munro, C.F., Miller, D.I. and Fugevand, A.J. (1987) Ground reaction
     forces in running. A reevaluation. Journal of Biomechanics 20:

     Nachbauer, W. & Nigg, B.M (1992) Effects of arch height of the foot
     on ground reaction forces in running. Med Sci Sports Ex
     24:1264-1269. Nigg, B.M. (Ed) (1986) Biomechanics of Running
     Shoes. Champaign IL, Human Kinetics.

     Nigg, B.M., Bahlsen, H.A. Luethi, S.M., and Stokes, S. (1987) The
     influence of running velocity and midsole hardness on external
     impact forces in heel-toe running. Journal of Biomechanics 20:

     Nigg, B.M., Herzog, W. and Read J.L. Effect of viscoelastic shoe
     insoles on vertical impact forces in heel-toe running. Am. J. Sports
     Med. 16:70-76.

     Noe, D.A., Voto, S.J., et al, (1993) Role of the calcaneal heel pad
     and polyumeric shock absorbers in attenuation of heel strike impact.
     J. Biomed Engng 15: 23-26.

     Oakley, T. And Pratt, D.J.. (1988) Skeletal transients during heel and
     toe strike running and the effectiveness of some materials in their
     attenuation. Clinical Biomecahnics, 3: 159-165.

     Valiant G.A., McMahon, T.A. and Frederick, E.C. (1987) A new test
     to evaluate the cushioning properties of athletic shoes. In B.
     Jonsson (Ed) Biomechanics X-B (pp 937-941). Champaign, IL,
     Human Kinetics.

     Voloshin,A.S., Burger, C.P. et al: (1985) An in-vivo evaluation of the
     leg's shock absorbing capacity. In Winter et al (Eds) Biomechanics
     IX-B (pp 112-116) Champaign, IL., Human Kinetics.

     Voloshin, A.S. and Wosk, J. (1982) An in-vivo study of low back pain and shock absorption in the human locomotor system. J. Biomechanics 15, 21-27.

     Wosk, J. & Voloshin, A.S. (1981) Wave attenuation in the skeletons
     of young heallthy persons. J. Biomechanics 14:261-267

Plantar pressure distribution

     Aritomi, H., Morita, M. and Yonemoto, K. (1983) A simple method of
     measuring the footsole pressure of normal subjects using pre-scale
     pressure-detecting sheets. J. Biomechanics 16:157-165.

     Cavanagh, P.R. and Ae, M. (1980) A technique for the display of
     pressure distribution data beneath the foot. J. Biomech 13:69-75.

     Cavanagh, P.R. and Hennig E.M. (1982) A new device for the
     measurement of pressure distribution on a rigid surface. Med. Sci
     Sports Ex. 14: 153p

     Hennig, E.M and Rosenbaum, D. (1991) Pressure distribution under
     the feet of children in comparison with adults. Foot and Ankle

     Hennig, E.M., Cavanagh, P.R. and Macmillan, N.H. (1983) Pressure
     distribution easurements by high precision piezo-ceramic force
     transducers. pp 1081-1088 in H. Matsui and K. Kobayashi (Eds)
     Biomechanics VII-B, Champaign, IL, Human Kinetics.

     Hennig, E.M., Valiant G.A. & Liu,Q. (1993) Relationships between
     perception of cushioning and pressure distribution parameters in
     running shoes. Pp564-565 in Bioouisett et al (Eds) Biomechanics
     XIV Paris: International Society of Biomechanics.

     Shorten, M.R., Eden, K.B and Himmelsbach, J.A. (1989) Plantar
     pressure distribution during barefoot walking. Proc XII International
     Congress of Biomechanics (Edited by Gregor, R. J., Zernicke, R. F.
     and Whiting, W. C.), #120. Department of Kinesiology, UCLA, Los
     Angeles, Ca.

     Shorten, M. R. and Winslow, D. S. (1989) Multiple element model of
     running shoe cushioning. Proc 13th Ann. Meeting Am. Soc.
     Biomech., pp. 88-89. University of Vermont, Burlington, Vt.

     Shorten, M.R. and Winslow D.S.(1992) Spectral analysis of impact
     shock during running. Int. J. Sports Biomechanics 8:288-304

     Smeathers, J.E. (1989) Measurement of transmissibility for the
     human spine during walking and running. Clinical Biomechanics 4:

     Snel, J. G., Delleman, N. J., Heerkens, Y. F. and van Ingen Schenau,
     G. J. (1985) Shock absorbing characteristics of running shoes during
     actual running. Biomechanics IX-B (Edited by Winter, D. A., Norman,
     R. W., Wells, R. P., Hayes, K. R. and Patla, A. E.), pp. 133-137.
     Human Kinetics Publ, Champaign, Il.

Foot structure and function

     Aerts, P. And De Clerq, D (1993) Deformation characteristics of the
     heel region of the shod foot during a simulated heel strike: the effect
     of varying midsole hardness. J. Sports Sci 11:449-461.

     Alexander, R. McN. and Bennet Clark, H. C. (1977) Storage of strain energy in muscles and other tissues. Nature, Lond. 265, 114-117.

     Bennett, M.B. and Ker, R.F. (1990) The mechanical properties of the
     human subcalcaneal fat pad in compression. J. Anatomy. 171:

     Bojsen-Moeller, F. (1978) The human foot, a two speed
     construction. pp 261-266 in Asmussen E. and Jorgensen, K. (Eds)
     Biomechanics VI-A., Baltimore, IL, University Park Press.

     Bojsen-Moeller, F. (!979) Calcaneocuboid joint and stability of the
     longitudinal arch of the foot at high gear and low gear push-off. J.
     Anatomy, 129:165-176

     De Clercq, D. Aerts, P and Kunnen, M. (1994) The mechanical
     characteristics of the human heel pad during foot strike in running: an
     in vivo cineradiographics study. J. Biomechanics 27: 1213-1222.

     Ker, R. F., Bennett, M. B., Bibby, S. R., Kester, R. C. and Alexander, R. McN. (1987) The spring in the arch of the human foot. Nature, Lond. 325, 147-149.

     Hawes, M.R. and Sovak, D. (1994) Quantitative morphology of the
     human foot in a North American population. Ergonomics

     Holden J.P., Cavanagh, P.R., Williams, K.R., and Bednarski, K.R.
     (1983). Foot angles during walking and running. In D.A. Winter, R.W. Norman, R.P. Wells, K.C. Hayes and A.E. Patla (Eds.),
     Biomechanics IX-A, 451-457, Champaign, IL: Human Kinetics
     Publishers, Inc.

     Inman, V.T. (1976). The joints of the ankle. Baltimore: Williams and
     Wilkins Co.

     Kernozek, T.W. and Ricard, M.D. (1990). Foot placement angle and
     arch type: effect on rearfoot motion. Archives of Physical Medicine
     and Rehabilitation, 71, 988-991.

     Kinoshita, H. Ogawa, T., Kuzuhara, K. And Ikuta, K. (1993) In vivo
     examination of the dynamic properties of the human heel pad. Int. J.
     Sports Med. 14: 312-319.

     McMahon, T.A. (1987) The spring in the human foot. Nature, Lond.
     325, 108-109.

Control of GRFs

     Areblad, M., Nigg. B.M. et al (1990) Three dimensional
     measurement of rearfoot control during running. J. Biomechanics 23:

     Bates, B., Osternig L.R., Mason, B. and James, S.L. (1978) Lower
     extremity function during the support phase of running. pp 30-39 in
     Asmussen et al (Eds) Biomechanics VI-B, University Park Press,

     Bates, B., Osternig L.R., Mason, B. and James, S.L. (1979a) Foot
     orthotic devices to modify selected aspects of lower extremity
     mechanics. Am J Sports Med 7:338-342

     Bates, B., Osternig L.R., Mason, B. and James, S.L. (1979b)
     Functional variability of the lower extremity during the support phase
     of running. Med Sci Sports Ex. 11: 328-331.

     Bauer, H. (1970) The effect of high top and low cut football shoes on
     speed and agility. Athletic Journal 50:74.

     Clarke, T. E., Frederick, E. C. and Hamill, C.L. (1983) The effects of
     shoe design parameters on rearfoot control during running. Med Sci
     Sports Ex. 15:376-381.

     Clarke, T.E., Frederick, E.C., and Hamill, C.L. (1984). The study of
     rearfoot movement in running. In E.C. Frederick (Ed.), Sport shoes
     and playing surfaces (pp. 166-189). Champaign, IL: Human Kinetics

     Edington, C.J., Frederick. E.C. and Cavanagh, P.R. (1990) Rearfoot
     motion in distance running. pp 135-164 in P.R. Cavanagh (Ed)
     Biomechanics of distance running. Champaign, IL, Human Kinetics.

     Engsberg, J.R. (1987) A biomechanical analysis of the talocalcaneal
     joint - in vitro. J. Biomechanics 20: 429- 442. Engsberg, J.R. and
     Andrews J.G. (1987) kinematic analysis of the
     talocalcaneal/talocrural joint during running support. Med Sci Sports
     Ex 19:169-184.

     Cornwall, M.W. and McPoil, T.G. (1993) Reducing 2-dimensional
     rearfoot motion variability during walking. J. Am Podiatr Ass.

     Milani, T.L., Schnabel, G and Hennig, E.M. (1995) Rearfoot motion
     and pressure distribution patterns during running in shoes with varus
     and valgus wedges. J. Applied Biomechanics 11: 177-187.

     D'Ambrosia, R., and Douglas, R. (1982). Orthotics. In R.
     D'Ambrosia and D. Drez (Eds.), Prevention and treatment of running
     injuries. New Jersey: Slade.

     Ferrandis, R., Garcia, R., Ramira, J., Hoyos, J and Vera, P. (1994)
     Rearfoot motion and torsion in running: the effects of upper vamp
     stabilisers. J. Applied Biomechanics 10:28-42.

     Hamill, J., Freedson, P.S., Boda, W., and Reichsman, F. (1987).
     Effects of shoe type on cardiorespiratory responses and rearfoot
     motion during treadmill running. Medicine and Science in Sports and
     Exercise, 20, 515-521.

     Nigg, B.M and Bahlsen, H.A. (1988) Influence of heel flare and
     midsole construction on pronation, supination and impact forces for
     heel-toe running. Int. J. Sports Biomechanics 4:205-219.

     Nigg, B.M., Luethi, S.M., Stacoff, A., and Segesser, B. (1984).
     Biomechanical effects of pain and sport shoe corrections. The
     Australian Journal of Science and Medicine, 16, 10-16.

     Nigg, B.M and Morlock, M. (1987) The influence of lateral heel flare
     of running shoes on pronation and impact force. Med. Sci Sports
     Ex. 19: 294-301

     Pope, M.H., Renstrom, P., Donnermeyer, D., and Morgenstern, S.
     (1987). A comparison of ankle taping methods. Medicine and
     Science in Sports and Exercise, 19, 143-147.

     Procter, P., Berme, N., and Paul, J.P. (1981). Ankle joint
     biomechanics. In A. Morecki, K. Fidelus, K. Kedizor, and A. Wit
     (Eds.), Biomechanics VII-A (pp. 52-56). Baltimore: University Park

     Quinn, T.P., Mote Jr., C.D., and Skinner, H.B. (1991). The effect of
     ankle constraint on the torsional laxity of the knee during
     internal-external rotation of the foot. Journal of Biomechanics, 24,

     Reinschmidt, C., and Nigg, B.M. (1995) Influence of heel height on
     ankle joint moments in running. Med Sci Sports Ex 27:410-416.

     Rodgers, M.M. and LeVeau, B.F. (1982) Effectiveness of foot
     orthotic devices used to modify pronation in runners. J. Orthopaedic
     and Sports Physical Therapy. 4:86-90.

     Robinson, J.R., Frederick, E.C. and Cooper, L.B. (1986) Systematic
     ankle stabilisation and the effect on performance. Med Sci Sports
     Ex 18: 625-628.

     Smith, M., Clarke, T., Hamill, C. and Santopietro, F. (1986) The
     effect of soft and semi-rigid orthoses upon rearfoot motion in
     running. Podiatric Sports Medicine 76:227-233.

     Stacoff, A., and Kaelin, X. (1983). Pronation and sport shoe design.
     In B.M. Nigg and B.A. Kerr (Eds.), Biomechanical aspects of-sport
     shoes and playing surfaces (pp. 143- 151). Calgary: University
     Printing. Stacoff, A.,

     Stuessi, E. & Sondereger, D. (1983). Lateral stability of sports
     shoes. In Winter D.A. (Ed) Biomechanics IX, Champaign, IL, Human Kinetics. Stacoff, A., Denoth, J., Kaelin, X.,

     Stacoff, A., Kaelin, X., Stuessi, E. and Segesser, B. (1989) The
     torsion of the foot in running. Int. J. Sports Biomechanics. 5:

     Stacoff, A., Kaelin, X. and Stuessi, E. (1991) The effects of shoes
     on torsion and rearfoot motion in running. Med Sci Sports Ex.
     23:482-490. Sousas-Little, R.W., Beavis G.C.,

     Verstraete, M.C. & Markus, T.L. (1987) Analysis of foot motion
     during running using a joint coordinate system. Medicine and
     Science in Sports and Exercise 19:285-293.

     Vagenas, G., and Hoshizaki, B. (1988). Evaluation of rearfoot
     asymmetries in running with worn and new running shoes.
     International Journal of Sports Biomechanics , 4, 220- 230.

     Van Gheluwe, B., Tielemans, R. and Roosen, P. The influence of
     heel counter rigidity on rearfoot motion during running. J. Applied
     Biomechanics 11:47-67.

     Williams, K.R. (1982). Non-saggital plane movements and forces
     during distance running. Proceedings of the Sixth Annual Conference
     of the ASB.


     Bowers, K.D. and Martin, R.B. (1975) Cleat surface friction on new
     and old Astroturf. Med Sci Sports Ex. 7:132. (Abstract)

     Morehouse, C.A. and Niebel, B.W. (1975) Torques developed by
     different types of shoes on various playing surfaces. Med Sci
     Sports Ex. 7:127-131.

     Perkins, P.J. and Wilson, M.P., Slip resistance testing of shoes -
     new developments. Ergonomics 26:73-82.

     Rheinstein, D.J., Morehouse, C.A. and Niebel, B.W. Effects on
     traction of outsole composition and hardnesses of basketball shoes
     and three types of playing surfaces. Med Sci Sports Ex 10:282-288.

     Unold, E. and Nigg, B.M. (1983) The frictional characteristics of
     tennis shoes. pp153-160 in Nigg, B.M and Kerr, B.A (Eds)
     Biomechanical aspects of sports shoes and playing surfaces.
     University Printing, Calgary.

     Valiant G.A. (1986) The effect of outsole pattern on basketball shoe
     traction. Pp 29-37 in J. Terauds (Ed) Biomechanics in Sports III &
     IV. DelMar, CA, Academic Publishers.

     Valiant, G.A. (1988) Ground reaction forces developed on artificial
     turf. pp 406-415 in Science and Football (Ed T. Reilly et al ) London,
     E.&F.N. Spon.

     Valiant, G.A. (1989) Transmission and attenuation of heel strike
     accelerations. Pp 225-247 in P.R. Cavanagh (Ed) The biomehanics
     of distance running. Champaign, IL.. Human Kinetics.

     Valiant, G.A. and Cavanagh, P.R. (1983) A study of landing from a
     jump: implications for the designj of a basketball shoe. In Winter D.A
     (Ed) Biomechanics IX, Champaign, IL, Human Kinetics.

     Torg J.S. and Quedenfeld T.C. (1971) Effect of shoe type and cleat
     length on the incidence and severity of knee injuries among
     Philadelphia High School football players. Res Quart 42:203-211.

     Van Gheluwe, B., Deporte, E. and Hebbelinck, M. Frictional forces
     and torques of soccer shoes on artificial turf. pp161-168 in Nigg,
     B.M and Kerr, B.A (Eds) Biomechanical aspects of sports shoes
     and playing surfaces. University Printing, Calgary.


     Alexander, R. McN. (1987) The spring in your step. New Scientist,
     April 30, 1987, pp 42-44.

     Alexander, R. McN.(1988) The spring in your step: the role of elastic
     mechanisms in human running. Biomechanics XI-A (Edited by de
     Groot, G., Hollander, A. P., Huijing, P. A. and van Ingen Schenau, G.
     J.), pp. 17-25. Free University Press, Amsterdam.

     Alexander, R. McN. (1991) Energy-saving mechanisms in walking
     and running. J. exp. Biol. 160: 55-69.

     Clement, D.B., Taunton, J.E. Wiley, J.P., Smart. G.W. and
     McNichol, K.L. (1982) Investigation of metabolic efficiency in
     runners with and without corrective orthotic devices. Int. J. Sports
     Med. 2: 14-15.

     Frederick, E.C., Howley, E.T., and Powers, S.K. (1980). Lower O2
     cost while running on air cushion type shoe. Medicine and Science in
     Sports and Exercise, 12, 81-82.

     Frederick, E. C., and Powers, S. K. (1986) Lower oxygen demands
     of running in soft soled shoes. Res. Quart. Ex. Sport 57, 174-177.

     Frederick, E. C., Clarke, T. E., Larsen, J. L. and Cooper, L. B.
     (1983) The effects of shoe cushioning on the oxygen demands of
     running. Biomechanical Aspects of Sports Shoes and Playing
     Surfaces (Edited by Nigg, B. M. and Kerr, B. A.), pp. 107-114. The
     University of Calgary, Calgary.

     Glieck, J.A. (1987) Running shoes waste natural energy of feet. New
     York Times, June 2, 1987, p 19.

     Hammill, J., Freedson, P.S., Boda, W., and Reichsman, F. (1987).
     Effects of shoe type on cardiorespiratory responses and rearfoot
     motion during treadmill running. Medicine and Science in Sports and
     Exercise, 20, 515-521.

     Hayes, J., Smith, L., and Sanpietro, F. (1983). The effect of
     orthotics on the aerobic demands of running. Medicine and Science
     in Sports and Exercise, 15, 169.

     Shorten, M. R. (1989) Elastic energy in athletic shoe cushioning
     systems. Proc. XII International Congress of Biomechanics (Edited
     by Gregor, R. J., Zernicke, R. F. and Whiting, W. C.), #120.
     Department of Kinesiology, UCLA, Los Angeles, Ca.

     Shorten, M. R. (1992) The Energetics of Running and Running
     Shoes. J. Biomechanics 26: S41-51.

Injury mechanisms

     Bowers, K.D. and Martin, R.B. (1976) Turf-toe: a shoe-surface
     related football injury.Med Sci Sports Ex. 8(2):81-83.

     Brubaker, C.E., and James, S.L. (1974). Injuries to runners. Journal
     of Sports Medicine, 2, 189-199.

     Clement, D.B., Taunton, J.E., and Smart, G.W. (1984). Achilles
     tendinitis and peritendinitis: Etiology and treatment. American
     Joumal of Sports Medicine, 12, 179-184.

     Clement, D.B., Taunton, J.E., Smart. G.W. and McNichol, K.L.
     (1981) A survey of overuse injuries in running. Physician and
     Sportsmedicine 9:47-58

     Cox, J.S. (1985) Patellofemoral problems in runners. Clinics in
     Sports Medicine 4:699-715.

     Detmer D.E. (1986) Chronic shin splints classification and
     management of medial tibial stress syndrome. Sports Medicine 3:

     Jackson, D.W. (1978). Shinsplints: an update. Physician Sports
     Medicine, 6, 49-68.

     James, S.L., Bates, B.T. and Osternig,. L.R. (1978) Injuries to
     runners. Am. J. Sports Medicine 6: 40-49.

     Gardner, L.I et al (1988) Prevention of lower extremity stress
     fractures: a controlled trial of a shock absorbent insole. Am J. Public
     Health 78: 1563-1567.

     Krissoff, W.B., and Ferris, W.D. (1979). Runner's injuries. The
     Physician and Sports Medicine, 7:12, 55-64.

     Leach, R. (1982). Running injuries of the knee. In R. D'Ambrosia and
     D. Drez (Eds.), Prevention and treatment of running injuries (pp.
     55-75). New Jersey: Slade.

     Marcus, B. (1983). The influence of footwear and surfaces on
     performance and injury potential in running. Unpublished doctoral
     dissertation. Imperial College, University of London.

     McKenzie, D.C. Clement, D.B. & Taunton, J.D. (1985) Running
     shoes, orthotics and injuries. Sports Medicine 2: 334- 337.

     Messier, S.P. and Pittala, K.A. (1988) Etiologic factors associated
     with selected running injuries. Med Sci Sports Ex. 20: 501-505.

     Milgrom, C., Giladi, M, et al (1985) A prospective study of the effect
     of a shock absorbing orthotic device on the incidence of stress
     fractures in military recruits. Foot and Ankle 6: 101-104.

     Miller, B.J., Pate R.R. and Burgess, W. (1988) Foot impact force
     and intravascular hemolysis during distance running. Int. J. Sports
     Medicine, 9: 56-60.

     Smart, G.W., Taunton, J.E. and Clement, D.B. Achilles tendon
     disorders in runners: a review. Med Sci Sports 12: 231- 243.

     Stuessi, E. (1988) Running injuries and shoe construction: some
     possible relationships. Int. J. Sports Biomech 4: 342-357.

     Subotnick, S.I. (1979). Cures for common running injuries. Mountain
     View, CA:Anderson World, Inc.

     Subotnick, S.I. (1980). The cavus foot. Physician and Sports
     Medicine, 8(7):53-55

     Subotnick, S.I. (1981). The flat foot. Physician and Sports Medicine,
     9, 85-91.

     Taunton, J.E., Clement, D.B. & McNichol, K. (1982) Plantar fasciitis
     in runners. Canadian J. Applied Sports Science 7:41-44.

     Tiberio, D. (1987). The effect of excessive sub-talar joint pronation
     on patellofemoral mechanics : a theoretical model. Journal of
     Orthopaedic and Sports Physical Therapy, 9:160-165.

     Other shoe characteristics

     Caitlin, M.E., and Dressenhofer, R.F. (1979). Effects of shoe weight
     on the energy cost of running. Medicine and Science in Sports and
     Exercise, 11, 80.

Running style

     Frederick, E. C. (1986) Kinematically mediated effects of sport shoe
     design: a review. J. Sports Sci. 4, 169-184.

     Williams, K.R., and Ziff, J.L. (1991). Changes in distance running
     mechanics due to systematic variations in running style. International
     Journal of Sports Biomechanics, 7, 76-90.

McMahon, T. A., Valiant, G.A. and Frederick, E.C. (1987) Groucho
     running. Journal of Applied Physiology 62: 2326- 2337.

Sports Surfaces

     Amirouche,F.M. (1987).  Modeling of human reactions to
     whole-body vibration.  J.Biomech.Eng,  109(3), 210-217.

     Anderson,T. (1996).  Biomechanics and running economy.  Sports
     Med,   22(2), 76-89.

     Andreasson,G., Lindenberger,U., Renstrom,P., & Peterson,L.
     (1986).   Torque developed at simulated sliding between sport shoes
     and an artificial turf.  Am J Sports Med,  14(3), 225-230.

     Arendt,E., & Dick,R. (1995).  Knee injury patterns among men and
     women in collegiate basketball and soccer. NCAA data and review
     of literature.  Am J Sports Med,   23(6), 694-701.

     Bahniuk,E., & Zamir,I. (1976).  Characteristics of antifriction devices
     used for ski bindings.  Orthop.Clin.North Am.,  7 (1), 105-115.

     Barrett,R.S., Neal,R.J., & Roberts,L.J. (1998).  The dynamic loading
     response of surfaces encountered in beach running.   J Sci Med
     Sport,  1(1), 1-11.

     Bassey,E.J., Littlewood,J.J., & Taylor,S.J. (1997).  Relations
     between compressive axial forces in an instrumented massive
     femoral implant, ground reaction forces, and integrated
     electromyographs from vastus lateralis during various 'osteogenic'
     exercises.  J Biomech,  30(3), 213-223.

     Bednarczyk,J.H., & Sanderson,D.J. (1994).  Kinematics of
     wheelchair propulsion in adults and children with spinal cord injury.
     Arch Phys Med Rehabil,  75(12), 1327-1334.

     Blickhan,R. (1989).  The spring-mass model for running and
     hopping.  J Biomech,  22(11-12), 1217-1227.

     Bobbert,M.F., Schamhardt,H.C., & Nigg,B.M. (1991).  Calculation of
     vertical ground reaction force estimates during running from
     positional data.  J Biomech,  24(12), 1095-1105.

     Bobbert,M.F., Yeadon,M.R., & Nigg,B.M. (1992).  Mechanical
     analysis of the landing phase in heel-toe running.  J Biomech,  25(3),

     Bodnar,J. (1987).  Sports Surfaces: The Right Stuff Underfoot.
     Construction Specifier,  v 40(n 6), 110-112, 114, 116.

     Bonstingl,R.W., Morehouse,C.A., & Niebel,B.W. (1975).  Torques
     developed by different types of shoes on various playing surfaces.
     Med Sci Sports,  7(2), 127-131.

     Bosco,C., Saggini,R., & Viru,A. (1997).  The influence of different
     floor stiffness on mechanical efficiency of leg extensor muscle.
     Ergonomics,  40(6), 670-679.

     Bowers,K.D.J., & Martin,R.B. (1975).  Cleat-surface friction on new
     and old AstroTurf.  Med Sci Sports,   7(2), 132-135.

     Bowers,K.D.J., & Martin,R.B. (1976).  Turf-toe: a shoe-surface
     related football injury.  Med Sci Sports,   8(2), 81-83.

     Bowers, K.D. and Martin, R.B. (1974) Impact absorption, new and
     old Astroturf at West Virginia University. Med Sci Sports Ex.

     Briss,P.A., Sacks,J.J., Addiss,D.G., Kresnow,M., & O'Neil,J.
     (1994).  A nationwide study of the risk of injury associated with day
     care center attendance [see comments].  Pediatrics,   93(3),

     Briss,P.A., Sacks,J.J., Addiss,D.G., Kresnow,M.J., & O'Neil,J.
     (1995).  Injuries from falls on playgrounds. Effects of day care center
     regulation and enforcement.  Arch Pediatr Adolesc Med,  149(8),

     Brown,M., Rudicel,S., & Esquenazi,A. (1996).  Measurement of
     dynamic pressures at the shoe-foot interface during normal walking
     with various foot orthoses using the FSCAN system.  Foot Ankle Int,
       17(3), 152-156.

     Brown,R.P. (1982).  Specifications And Tests For Artificial Sports
     Surfaces.  Polymer Testing,  v 3(n 2), 85-98.

     Brown,R.P. (1987).  Performance Tests For Artificial Sports
     Surfaces.  Polymer Testing,  v 7(n 4), 279-292.

     Buczek,F.L., & Cavanagh,P.R. (1990).  Stance phase knee and
     ankle kinematics and kinetics during level and downhill running.  Med
     Sci Sports Exerc,  22(5), 669-677.

     Buttermann,G.R., Janevic,J.T., Lewis,J.L., Lindquist,C.M.,
     Wood,K.B., & Schendel,M.J. (1994).  Description and application of
     instrumented staples for measuring in vivo bone strain.  J Biomech,
     27(8), 1087-1094.

     Bylak,J., & Hutchinson,M.R. (1998).  Common sports injuries in
     young tennis players.  Sports Med.,   26(2), 119-132.

     Chaffin,D.B., Woldstad,J.C., & Trujillo,A. (1992).  Floor/shoe slip
     resistance measurement.  Am Ind Hyg Assoc J,  53(5), 283-289.

     Chapman,A.E., Lonergan,R., & Caldwell,G.E. (1984).  Kinetic
     sources of lower-limb angular displacement in the recovery phase of
     sprinting.  Med Sci Sports Exerc,  16(4), 382-388.

     Chapman,A.E., Leyland,A.J., Ross,S.M., & Ryall,M. (1991).  Effect
     of floor conditions upon frictional characteristics of squash court
     shoes.  J Sports Sci,  9(1), 33-41.

     Charteris,J. (1998).   Comparison of the effects of backpack loading
     and of walking speed on foot-floor contact patterns.  Ergonomics,
     41(12), 1792-1809.

     Chen,H.  Relationship between plantar pressure distribution under
     the foot and insole comfort.  Clinical Biomechanics 9 6 Nov 1994,

     Chesney,D.A. (1996).   Preliminary test method for the determination
     of surface firmness.  IEEE Transactions on Rehabilitation
     Engineering v 4 n 3 Sep 1996,  4(3), 182-187, ISSN.

     Chiu,J., & Robinovitch,S.N. (1998).  Prediction of upper extremity
     impact forces during falls on the outstretched hand [In Process
     Citation].   J Biomech,  31(12), 1169-1176.

     Clanton,C., Kobluk,C., Robinson,R.A., & Gordon,B. (1991).
     Monitoring surface conditions of a Thoroughbred racetrack.
     J.Am.Vet.Med.Assoc.,  198(4), 613-620.

     Clement,D.B., & Taunton,J.E. (1981).  A guide to the prevention of
     running injuries.  Aust Fam Physician,  10(3), 156-4.

     Coker,T.P., Arnold,J.A., & Weber,D.L. (1978).  Traumatic lesions of
     the metatarsophalangeal joint of the great toe in athletes.
     Am.J.Sports Med.,  6(6), 326-334.

     Colbeck,S.C. (1994).   A review of the friction of snow skis.   J
     Sports Sci,  12(3), 285-295.

     Colbeck,S.C. (1995).   Electrical charging of skis gliding on snow.
     Med Sci Sports Exerc,  27(1), 136-141.

     Creagh,U., Reilly,T., & Lees,A. (1998).  Kinematics of running on
     'off-road' terrain.  Ergonomics,  41(7), 1029-1033.

     Creagh,U., & Reilly,T. (1998).  Training and injuries amongst elite
     female orienteers.  J.Sports Med.Phys.Fitness,  38(1), 75-79.

     Davis,B.L., & Cavanagh,P.R. (1993).  Simulating reduced gravity: a
     review of biomechanical issues pertaining to human locomotion.
     Aviat Space Environ Med,  64(6), 557-566.

     de Koning,J.J., de Groot,G., & van Ingen,S. (1992).  Ice friction
     during speed skating.  J Biomech,   25(6), 565-571.

     de Koning,J.J., Nigg,B.M., & Gerritsen,K.G. (1997).  Assessment of
     the mechanical properties of area-elastic sport surfaces with video
     analysis.  Med Sci Sports Exerc,  29(12), 1664-1668.

     Dufek,J.S., & Bates,B.T. (1991).  Biomechanical factors associated
     with injury during landing in jump sports.  Sports Med,  12(5),

     Ekstrand,J., & Nigg,B.M. (1989).  Surface-related injuries in soccer.
     Sports Med,   8(1), 56-62.

     Feehery,R.V., Jr. (1986).   The biomechanics of running on different
     surfaces.  Clin.Podiatr.Med.Surg.,  3(4), 649-659.

     Fendley,A. (1995).  Development of an athlete/shoe/surface-related
     injury prediction model for American football. Part 1: systematic
     identification of qualitative and quantitative variables.  Southern
     Biomedical Engineering Conference - Proceedings 1995,
     (Biomedical), 150-153, Coden.

     Ferris,D.P., Louie,M., & Farley,C.T. (1998).  Running in the real
     world: adjusting leg stiffness for different surfaces.  Proc R Soc
     Lond B Biol Sci,  265(1400), 989-994.

     Flynn,T.W., Canavan,P.K., Cavanagh,P.R., & Chiang,J.H. (1997).
     Plantar pressure reduction in an incremental weight-bearing system.
     Phys Ther,  77(4), 410-416.

     Frederick,E.C. (1986).   Kinematically mediated effects of sport
     shoe design: a review.  J Sports Sci,   4(3), 169-184.

     Fukuda H. (1988) Biomechanical analysis of landing on surfaces with
     different stiffnesses. Biomechanics XI-B (Edited by de Groot, G.,
     Hollander, A. P., Huijing, P. A. and van Ingen Schenau, G. J.), pp
     679-684. Free University Press, Amsterdam.

     Gatto,F., Swannell,P., & Neal,R. (1992).  A force-indentation
     relationship for gymnastic mats.  J Biomech Eng,  114(3), 338-345.

     Gehlsen,G.M., Stewart,L.B., Van Nelson,C., & Bratz,J.S. (1989).
     Knee kinematics: the effects of running on cambers.  Med Sci
     Sports Exerc,  21(4), 463-466.

     Gerritsen,K.G., van den Bogert,A.J., & Nigg,B.M. (1995).  Direct
     dynamics simulation of the impact phase in heel-toe running.  J
     Biomech,  28(6), 661-668.

     Glaister,D.H. (1978).   Human tolerance to impact acceleration.
     Injury,  9(3), 191-198.

     Greene,P.R., & McMahon,T.A. (1979).  Running in circles.
     Physiologist,  22(6), S35-S36

     Greene,P.R. (1985).  Running on flat turns: experiments, theory, and
     applications.   J Biomech Eng,  107(2), 96-103.

     Gross,T.S., & Nelson,R.C. (1988).  The shock attenuation role of the
     ankle during landing from a vertical jump.  Med Sci Sports Exerc,
     20(5), 506-514.

     Gross,T.S., & Bunch,R.P. (1989).  Discrete normal plantar stress
     variations with running speed.  J Biomech,  22(6-7), 699-703.

     Gross,T.S., & Bunch,R.P. (1989).  Material moderation of plantar
     impact stress [see comments].  Med Sci Sports Exerc,  21 (5),

     Heidt,R.S.J., Dormer,S.G., Cawley,P.W., Scranton,P.E.J.,
     Losse,G., & Howard,M. (1996).  Differences in friction and torsional
     resistance in athletic shoe-turf surface interfaces.  Am J Sports Med,
       24(6), 834-842.

     Heudorf,U. (1993).  [Handling of red silica gravel on sports, play and
     resort surfaces with special reference to new toxicologic results].
     Gesundheitswesen,  55(10), 521-526.

     Iversen,J.R., & McMahon,T.A. (1992).  Running on an incline.  J
     Biomech Eng,   114(4), 435-441.

     Jorgensen,U. (1990).   Body load in heel-strike running: the effect of
     a firm heel counter.  Am J Sports Med,   18(2), 177-181.

     Keene,J.S., Narechania,R.G., Sachtjen,K.M., & Clancy,W.G.
     (1980).  artan Turf on trial. A comparison of intercollegiate football
     injuries occurring on natural grass and Tartan Turf.  Am.J.Sports
     Med.,  8(1), 43-47.

     Keller,C.S., Noyes,F.R., & Buncher,C.R. (1987).  The medical
     aspects of soccer injury epidemiology.  Am.J.Sports Med.,  15(3),

     Khosravi-Sichani,B., Hemami,H., & Yurkovich,S. (1992).  Energy
     transformations in human movement by contact.  J Biomech,  25(8),

     Kibler,W.B. (1993).  Injuries in adolescent and preadolescent soccer
     players.  Med.Sci.Sports Exerc.,  25(12), 1330-1332.

     King,A.I. (1993).  Progress of research on impact biomechanics.  J
     Biomech Eng,  115(4B), 582-587.

     Komi,P.V., Gollhofer,A., Schmidtbleicher,D., & Frick,U. (1987).
     Interaction between man and shoe in running: considerations for a
     more comprehensive measurement approach.  Int J Sports Med,
     8(3), 196-202.

     Krahenbuhl, G.S. (1974) Speed of movement with varying footwear
     conditions on synthetic turf and natural grass. Research Quarterly

     Lafortune,M.A., Henning,E., & Valiant,G.A. (1995).  Tibial shock
     measured with bone and skin mounted transducers.  J Biomech,
     28(8), 989-993.

     Langley,J., & Crosado,B. (1984).  Two safety aspects of public
     playground climbing equipment.  N Z Med J,  97(758), 404-406.

     Leach,D.H., & Dagg,A.I. (1983).  A review of research on equine
     locomotion and biomechanics.  Equine Vet J,  15(2), 93-102.

     Lees,A., & Nolan,L. (1998).  The biomechanics of soccer: a review.
     J Sports Sci,   16(3), 211-234.

     Lehman,R.C. (1988).  Surface and equipment variables in tennis
     injuries.  Clin.Sports Med.,  7(2), 229-232.

     Lejeune,T.M., Willems,P.A., & Heglund,N.C. (1998).  Mechanics and energetics of human locomotion on sand.  J Exp Biol,  201 ( Pt 13),

     Levy,I.M., Skovron,M.L., & Agel,J. (1990).  Living with artificial
     grass: a knowledge update. Part 1: Basic science.  Am.J.Sports
     Med.,  18(4), 406-412.

     Lewis,L.M., Naunheim,R., Standeven,J., & Naunheim,K.S. (1993).
     Quantitation of impact attenuation of different playground surfaces
     under various environmental conditions using a tri-axial
     accelerometer.  J Trauma,  35(6), 932-935.

     Lillis,K.A., & Jaffe,D.M. (1997).  Playground injuries in children.
     Pediatr Emerg Care,  13(2), 149-153.

     Lord,M., Hosein,R., & Williams,R.B. (1992).  Method for in-shoe
     shear stress measurement.  J Biomed Eng,   14(3), 181-186.

     Louie,J.K., Kuo,C.Y., Gutierrez,M.D., & Mote,C.D.J. (1984).
     Surface EMG and torsion measurements during snow skiing:
     laboratory and field tests.  J Biomech,  17(10), 713-724.

     Mack,M.G., Hudson,S., & Thompson,D. (1997).  A descriptive
     analysis of children's playground injuries in the United States
     1990-4.   Inj Prev,  3(2), 100-103.

     Majid,F., & Bader,D.L. (1993).  A biomechanical analysis of the
     plantar surface of soccer shoes.  Proc Inst Mech Eng [H],  207(2),

     Martin,R.B., Liptai,L., Yerby,S., & Williams,K.R. (1994).  The
     relationship between mass and acceleration for impacts on padded
     surfaces [see comments].   J.Biomech.,  27(3), 361-364.

     Mavin,K.C. (1985).  Slip Resistance Of Footways And Sporting
     Surfaces.  National Conference Publication - Institution of
     Engineers, Australia, (n 85/14), 245-249.

     McCullagh,P.J., & Graham,I.D. (1985).  A preliminary investigation
     into the nature of shock absorbency in synthetic sports materials.  J
     Sports Sci,  3(2), 103-114.

     McGill,S.M. (1992).  A myoelectrically based dynamic
     three-dimensional model to predict loads on lumbar spine tissues
     during lateral bending.  J Biomech,  25(4), 395-414.

     McKenzie,D.C., Clement,D.B., & Taunton,J.E. (1985).  Running
     shoes, orthotics, and injuries.  Sports Med,   2(5), 334-347.

     McMahon,T.A. (1975).   Using body size to understand the structural
     design of animals: quadrupedal locomotion.  J Appl Physiol,  39(4),

     McMahon,T.A. (1979).   Gravitational scale effects.   Physiologist,
     22(6), S5-S6

     McMahon, T. A. and Greene, P. R. (1978) Fast running tracks.
     Scientific American 239:148-163.

     McMahon, T. A. and Greene, P. R. (1979) The influence of track
     compliance on running. J. Biomech 12:893-904.

     McMahon,T.A. (1987).   Biomechanics. The spring in the human foot [news].  Nature,  325(7000), 108-109.

     McMahon,T.A., & Cheng,G.C. (1990).  The mechanics of running:
     how does stiffness couple with speed?  J Biomech,  23 Suppl 1,

     Memari,A.M. (1994).  Linear and nonlinear finite element study of
     polyurethane used in sports shoes.  Advances in Structural
     Engineering Computing International Conference on Computational
     Structures Technology - Proceedings 1994, (Structural), Limited,
     Edinburgh, Scotl-87, Coden.

     Menck,H., & Jorgensen,U. (1983).  Frictional forces and ankle
     fractures in sport.  Br J Sports Med,   17(4), 135-136.

     Metzl,J.D. (1999).  Sports-specific concerns in the young athlete:
     football [In Process Citation].  Pediatr.Emerg.Care,  15(5), 363-367.

     Mikic,B., & Carter,D.R. (1995).  Bone strain gage data and
     theoretical models of functional adaptation.  J Biomech,  28(4),

     Milburn,P.D., & Barry,E.B. (1998).  Shoe-surface interaction and the
     reduction of injury in rugby union.  Sports Med,  25 (5), 319-327.

     Mizrahi,J., & Susak,Z. (1982).  In-vivo elastic and damping response
     of the human leg to impact forces.  J Biomech Eng,  104(1), 63-66.

     Mott,A., Evans,R., Rolfe,K., Potter,D., Kemp,K.W., & Sibert,J.R.
     (1994).  Patterns of injuries to children on public playgrounds.  Arch
     Dis Child,  71(4), 328-330.

     Mott,A., Rolfe,K., James,R., Evans,R., Kemp,A., Dunstan,F.,
     Kemp,K., & Sibert,J. (1997).  Safety of surfaces and equipment for
     children in playgrounds.   Lancet,  349(9069), 1874-1876.

     Myers,M.J., Steudel,K., & White,S.C. (1993).  Uncoupling the
     correlates of locomotor costs: a factorial approach.  J Exp Zool,
     265(3), 211-223.

     Nicholas,J.A., Rosenthal,P.P., & Gleim,G.W. (1988).  A historical
     perspective of injuries in professional football. Twenty- six years of
     game-related events.  JAMA,  260(7), 939-944.

     Nigg,B.M. (1985).  Biomechanics, load analysis and sports injuries in
     the lower extremities.   Sports Med.,  2(5), 367-379.

     Nigg,B.M., & Yeadon,M.R. (1987).  Assessment Of Vertical Surface
     Deformation Of Area Elastic Sport.  American Society of
     Mechanical Engineers, Design Engineering Division (Publication)
     DE,  v 13, 17

     Nigg,B.M., & Yeadon,M.R. (1987).  Biomechanical aspects of
     playing surfaces.  J Sports Sci,   5(2), 117-145.

     Nigg,B.M., & Segesser,B. (1988).  The influence of playing surfaces
     on the load on the locomotor system and on football and tennis
     injuries.   Sports Med,  5(6), 375-385.

     Nigg,B.M., Yeadon,M.R., & Herzog,W. (1988).  The influence of
     construction strategies of sprung surfaces on deformation during
     vertical jumps.  Med Sci Sports Exerc,  20(4), 396-402.

     Nigg,B.M. (1990).  The validity and relevance of tests used for the
     assessment of sports surfaces.  Med Sci Sports Exerc,  22(1),

     Nigg,B.M., De Boer,R.W., & Fisher,V. (1995).  A kinematic
     comparison of overground and treadmill running.  Med Sci Sports
     Exerc,  27(1), 98-105.

     Nigg,B.M., & Anton,M. (1995).  Energy aspects for elastic and
     viscous shoe soles and playing surfaces.  Med Sci Sports Exerc,
     27(1), 92-97.

     Nigg,B.M., Luethi,S., Denoth,J., & Stacoff,A. (1983).
     Methodological Aspects Of Sport Shoe And Sport Surface
     Analysis.  Biomechanics In Sport - A 1987 Update   International
     Series on Biomechanics,  v 4B, 1041-1052.

     Nilsson,J., Thorstensson,A., & Halbertsma,J. (1985).  Changes in
     leg movements and muscle activity with speed of locomotion and
     mode of progression in humans.   Acta Physiol Scand,  123(4),

     Novick,A., Stone,J., Birke,J.A., Brasseaux,D.M., Broussard,J.B.,
     Hoard,A.S., & Hawkins,E.S. (1993).   Reduction of plantar pressure
     with the rigid relief orthosis.  J Am Podiatr Med Assoc,  83(3),

     Oberg,B., Moller,M., Gillquist,J., & Ekstrand,J. (1986).  Isokinetic
     torque levels for knee extensors and knee flexors in soccer players.
     Int J Sports Med,  7(1), 50-53.

     Oggero,E., Pagnacco,G., Morr,D.R., Barnes,S.Z., & Berme,N.
     (1997).  The mechanics of drop landing on a flat surface--a
     preliminary study.  Biomed Sci Instrum,  33, 53-58.

     Ozguven,H.N., & Berme,N. (1988).  An experimental and analytical
     study of impact forces during human jumping.  J Biomech,  21(12),

     Powell,J.W., & Schootman,M. (1992).  A multivariate risk analysis of
     selected playing surfaces in the National Football League: 1980 to
     1989. An epidemiologic study of knee injuries.  Am.J.Sports Med.,
     20(6), 686-694.

     Recuero,A. (1995).  Uneven dynamic response of floors in a sports
     pavilion.  Computers and Structures v 55 n 1 Apr 3 1995,  55(1),
     185-189, ISSN.

     Redfern,M.S., Moore,P.L., & Yarsky,C.M. (1997).  The influence of
     flooring on standing balance among older persons.  Hum Factors,
     39(3), 445-455.

     Rheinstein,D.J., Morehouse,C.A., & Niebel,B.W. (1978).  Effects on
     traction of outsole composition and hardnesses of basketball shoes
     and three types of playing surfaces.  Med Sci Sports,   10(4),

     Robbins,S.E., Hanna,A.M., & Gouw,G.J. (1988).  Overload
     protection: avoidance response to heavy plantar surface loading.
     Med Sci Sports Exerc,  20(1), 85-92.

     Robbins,S.E., Gouw,G.J., & Hanna,A.M. (1989).  Running-related
     injury prevention through innate impact-moderating behavior.  Med
     Sci Sports Exerc,  21(2), 130-139.

     Robinovitch,S.N., Hayes,W.C., & McMahon,T.A. (1997).  Predicting
     the impact response of a nonlinear single-degree-of-freedom
     shock-absorbing system from the measured step response.  J
     Biomech Eng,   119 (3), 221-227.

     Robinovitch,S.N., & Chiu,J. (1998).  Surface stiffness affects impact
     force during a fall on the outstretched hand.  J Orthop Res,  16(3),

     Rodeo,S.A., O'Brien,S., Warren,R.F., Barnes,R., Wickiewicz,T.L., &
     Dillingham,M.F. (1990).  Turf-toe: an analysis of
     metatarsophalangeal joint sprains in professional football players.
     Am J Sports Med,  18(3), 280-285.

     Sands,W.A., Hondzinski,J.M., Shultz,B.B., & George,G.S. (1995).  A
     comparison of subtalar joint maximal eversion while jogging on the
     minitrampoline and floor.  J Orthop Sports Phys Ther,  22(2), 65-72.

     Savageau,M.A. (1985).   Mathematics of organizationally complex
     systems.  Biomed.Biochim.Acta,  44(6), 839-844.

     Schweizer,L.  Testing Procedures for Landing Mats, Surfaces for
     Floor Exercises and Vaulting Boards. (1985). Anonymous.  Institute
     for Sport and Sport Science, University of Freiburg, Freiburg,
     Germany:  International Gymnastics Federation.

     Scott,S.H., & Winter,D.A. (1993).  Biomechanical model of the
     human foot: kinematics and kinetics during the stance phase of
     walking.  J Biomech,  26(9), 1091-1104.

     Scranton,P.E.J., Whitesel,J.P., Powell,J.W., Dormer,S.G.,
     Heidt,R.S.J., Losse,G., & Cawley,P.W. (1997).  A review of selected
     noncontact anterior cruciate ligament injuries in the National Football
     League.  Foot Ankle Int,  18(12), 772-776.

     Shaw,J.E., Hsi,W.L., Ulbrecht,J.S., Norkitis,A., Becker,M.B., &
     Cavanagh,P.R. (1997).  The mechanism of plantar unloading in total
     contact casts: implications for design and clinical use.  Foot Ankle
     Int,  18(12), 809-817.

     Shiffer,R.C. (1994).   ASTM F-1292 as a tool for playground injury
     severity reduction.  ASTM Special Technical Publication n 1229
     1994, (n), 340-345, ISSN.

     Skovron,M.L., Levy,I.M., & Agel,J. (1990).  Living with artificial
     grass: a knowledge update. Part 2: Epidemiology.  Am.J.Sports
     Med.,  18(5), 510-513.

     Sosin,D.M., Keller,P., Sacks,J.J., Kresnow,M., & van Dyck,P.C.
     (1993).  Surface-specific fall injury rates on Utah school
     playgrounds.  Am J Public Health,  83(5), 733-735.

     Stanitski,C.L. (1989).   Common injuries in preadolescent and
     adolescent athletes. Recommendations for prevention.  Sports
     Med.,  7(1), 32-41.

     Steele,J.R. (1990).  Biomechanical factors affecting performance in
     netball. Implications for improving performance and injury reduction.
     Sports Med.,  10(2), 88-102.

     Sun,J., Walters,M., Svensson,N., & Lloyd,D. (1996).  The influence
     of surface slope on human gait characteristics: a study of urban
     pedestrians walking on an inclined surface.  Ergonomics,   39(4),

     Tang,P.F., & Woollacott,M.H. (1998).  Inefficient postural responses
     to unexpected slips during walking in older adults.  J Gerontol A Biol
     Sci Med Sci,  53(6), M471-M480

     Tomaro,J., & Burdett,R.G. (1993).  The effects of foot orthotics on
     the EMG activity of selected leg muscles during gait.  J Orthop
     Sports Phys Ther,  18(4), 532-536.

     Torg,J.S., Stilwell,G., & Rogers,K. (1996).  The effect of ambient
     temperature on the shoe-surface interface release coefficient.  Am J
     Sports Med,  24(1), 79-82.

     Valiant,G. (1999).  The effect of outsole pattern on basketball shoe
     traction.  Proceedings of ISBS: Biomechanics in Sports III & !V,

     van den Kroonenberg,A.J., Hayes,W.C., & McMahon,T.A. (1995).
     Dynamic models for sideways falls from standing height.  J Biomech
     Eng,  117(3), 309-318.

     van den,B.A., Read,L., & Nigg,B.M. (1996).  A method for inverse
     dynamic analysis using accelerometry.  J.Biomech.,  29(7), 949-954.

     van Weperen,W. (1991).   Overall approach to the safety of
     playgrounds.  Building and Environment Use and Safety Safety
     Science v 14 n 2 Aug 1991,  14(2), 103-108, ISSN.

     Veeger,D., van der Woude,L.H., & Rozendal,R.H. (1989).  The
     effect of rear wheel camber in manual wheelchair propulsion.  J
     Rehabil Res Dev,  26(2), 37-46.

     Viitasalo,J.T., Hamalainen,K., Mononen,H.V., Salo,A., & Lahtinen,J. (1993).  Biomechanical effects of fatigue during continuous hurdle jumping.   J Sports Sci,  11(6), 503-509.

     Wenger,W., & McIlhagger,R. (1992).  Surface-finish characteristics
     of composite components.  J Mater Process Technol v 33 n 4 Sep
     1992 p 439-452, ISSN 0924-0136, Coden JMPTEF, JA (Journal
     Article),  33 (4), 439-452, ISSN.

     Werner,P. (1982).  Playground injuries and voluntary product
     standards for home and public playgrounds.  Pediatrics,   69(1),

     Wilson,D.R., Neal,R.J., & Swannell,P. (1989).  The response of
     gymnastic sports floors to dyanmic loading.  Austrailian Journal of
     Science and Medicine in Sport,  21(1), 14-19.

     Yeadon,M.R., & Nigg,B.M. (1988).  A method for the assessment of
     area-elastic surfaces.  Med Sci Sports Exerc,  20(4), 403-407.

     Zebarth,B.J., & Sheard,R.W. (1985).  Impact and shear resistance of
     turf grass racing surfaces for Thoroughbreds.  Am.J.Vet.Res.,
     46(4), 778-784.

Disagree? Please email me!