Transcript Metabolic and Mechanical Energy Saving Mechanisms in Barefoot

Metabolic and Mechanical Energy
Saving Mechanisms in
Barefoot vs. Shod Human Running
Leslie Fischer
Honors Program and Division of Kinesiology and Health
Advisor: Dr. Matthew W. Bundle
Spring 2010
Background
Metabolic energy use during running
Metabolic Energy
Loaded
Running Speed
Muscle Function During Running
 No muscle length change during
stance
 Therefore muscles perform
little, to no, work during the
stance phase
 The job of the active muscle is to
provide force for weight support
Roberts et al., 1997
Muscle force production and metabolism
 The force generation step in
muscle requires ATP hydrolysis
(the energy currency of the cell)
 This provides for a link between
rates of muscle force production
and cellular energy release
Metabolic Energy α 1/tc
Kram & Taylor, 1990
Spring-like function of the human leg
 During the stance phase of
running the leg is under
compression and is shortest at
mid-stance
 Since muscle is isometric, this
length change occurs in the
tendons, and connective tissue
 This allows for the temporary
storage and release of elastic
energy within the large tendons
of our legs
Foot strike patterns and collision forces in
habitually barefoot versus shod runners
 Foot can collide with the ground in
three ways:
 Rear-foot strike (RFS)
 Mid-foot strike (MFS)
 Fore-foot strike (FFS)
 Evidence showing that barefoot
runners and minimally shod runners
avoid RFS
 Barefoot or minimally shod runners
are likely to be resistant to injury
Lieberman et al., 2010
VO2 (ml/kg/min)
Metabolic Energy
47
45.5
44
42.5
Barefoot
Shod
Vibram FiveFingers
Speed at 3.33 m/s
Cost of transport on average is 1.41%
less for barefoot running
Squadrone & Gallozzi, 2009
Contact Time
Average Contact Time (s)
0.3
Shod
0.25
Barefoot
Barefoot
Shod
Vibram
FiveFinger
0.2
Divert et al. 2005 and
Squadrone & Gallozzi 2009
Electromyography
Speed
was at
3.33 m/s
120
Relative
EMG Activity
100
80
Barefoot
Shod
60
40
20
0
Gastro. Lat.
Gastro. Med.
Soleus
Divert et al., 2005
Variables During Running
Expectations
Results
Energy Expended
Same
Less in Barefoot
Contact Time
Same
Less in Barefoot
EMG
Same
Greater in Barefoot
Question:
Why is it in-expensive to run barefoot?
Hypotheses:
1.) Massiveness of Limb
2.) Leg Stiffness
3.) Effective Mechanical Advantage (EMA)
1.) Massiveness of the limb
Constant Speed at 3.33m/s
VO2 (ml/kg/min)
45
42.5
40
37.5
35
No Load
Percent Differences:
0.50 kg thighs: 1.66%
0.50 kg feet: 3.34%
0.50 kg
Thighs
0.50 kg Feet
1.00 kg thighs: 3.53%
1.00 kg feet: 7.16%
1.00 kg
Thighs
1.00 kg Feet
Martin,1985
1.) Massiveness of the limb
60.0
0g
Additional
Weight
54.0
75 g
Additional
Weight
51.0
48.0
150 g
Additional
Weight
45.0
Speed (m/s)
5.0
4.5
4.0
42.0
3.5
VO2 (ml/kg/min)
57.0
225 g
Additional
Weight
Frederick, 1985
Metabolic Energy
Squadrone & Gallozzi, 2009
VO2 (ml/kg/min)
50
47.5
45
42.5
40
Barefoot
Shod
Speed at 3.33 m/s
Vibram
FiveFingers
2.) Leg Springs
•The tendons, ligaments, and muscles
in our legs function like springs
•The stiffness of the leg spring
kleg = Force
Δl
can change in response surface and
shoe compliance
2.) Stiffness
Lieberman et al., 2010
3.) Effective mechanical advantage (EMA)
Conclusion
References
Burkett, L.N., Kohrt, W.M., & Buchbinder, R. (1985). Effects of shoes and foot orthotics on VO2 and
selected frontal plane kinematics. Med Sci Sports Exerc, 17(1): 158-63.
De Wit, B., De Clercq, D., & Aerts, P. (2000). Biomechanical analysis of the stance phase during
barefoot and shoe running. J Biomech, 33(2):269-78.
Divert, C., Mornieux, G., Mayer F., & Belli, A. (2005) Mechanical comparison of barefoot and shod
running. Int J Sports Med, 26(7):593-8.
Frederick, E.C. (1983). A model of the energy cost of load carriage on the feet during running. Nike
Sport Research Laboratory, Exeter, New Hampshire, U.S.A.
Karm ,R. & Taylor, R. (1990). Energetics of running a new perspective. Nature, 346:265-267.
Martin, P.E. (1985). Mechanical and physiological responses to lower extremity loading during
running. Med Sci Sports Exerc, 17(4): 427-22.
Roberts, T.J., March, R.L., Weyand, P.G., Taylor, C.R. (1997). Muscular force in running turkey: the
economy of minimizing work. Science, 275:1113-1115,
Squadrone, R. and Gallozzi, C. (2009). Biomechanical and physiological comparison of barefoot and
two shod conditions in experienced barefoot runners. J Sports Med Phys Fitness, 49(1):6-13.