Running, Human Evolution, and Barefoot Running Review of Bramble & Lieberman (2004) Nature 432:...
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Transcript of Running, Human Evolution, and Barefoot Running Review of Bramble & Lieberman (2004) Nature 432:...
Running, Human Evolution, and Barefoot Running
Review of
Bramble & Lieberman (2004) Nature 432: 345-352
W. Rose
Austr. afarensis
Homo sapiens
Homo erectus
Present10 Mya 5 Mya 1.8 Mya3.5 Mya
Gorillas
Chimp-anzees
Human Evolutionary Timeline
Background
Australopithecines walked habitually > 4 Mya
H. erectus a better walking design than Australopith.: walking / swinging tradeoff
Was human running selected for? Did running influence human evolution?
Most have said probably not. Humans not very good sprinters. Horses, antelopes, greyhounds can run faster longer.
Sources: Bramble & Lieberman (2004) Nature 432: 345-352;.
Run vs. walkWalk
Inverted pendulum, KE – PE tradeoffC.o.m. vaults over extended leg in stanceU-shaped cost-of-transport (COT) curveOptimum speed a function of leg length
RunMass-spring mechanism, KE – PE tradeoffTendons, muscles, ligaments store PELimbs flex more in run to store energy
Walk-to-run transition occurs where COT curves intersect – as one might expectSources: Bramble & Lieberman (2004) Nature 432: 345-352.
Running gaitHuman running like trotting
Bipeds can’t gallopForelimbs move with opp. hindlimbsHuman running, trotting both bouncy
RunMass-spring mechanism, KE – PE tradeoffTendons, ligaments store PELimbs flex more in run to store energy
Walk-to-run where COT curves intersect
Sources: Bramble & Lieberman (2004) Nature 432: 345-352.
Endurance Running (ER)
ER: many kilometers, aerobically, 3-6.5 m/sHumans: only primates that do ERBetter than most mammalsHumans can run faster than most trotting animals trot, esp. when consider body sizeDistance: >10% Americans run kms/dayDistance: Thousands/yr run 42 kmUnknown in other primates; unusual in other mammals
Sources: Bramble & Lieberman (2004) Nature 432: 345-352.
Running Adaptations
What adaptations make ER possible?
When do they appear in fossil record?
Four areas of adaptation required for ER
• Energetics
• Strength
• Stabilization
• Thermoregulation
EnergeticsLong tendons, short muscles
Chimps: short calcaneal tendon
Australopithicus: Calcaneal tendon insertion site is chimplike
Plantar arch: another energy storage site in humans
Chimps: flat feet, weight bearing, large medial tuberosity on navicular.
Austr. like chimps, but early Homo lack large medial tuberosity on navicular
Bramble & Lieberman (2004) Nature 432: 345-352.
Energetics: Stride lengthHumans have longer stride than expected for animal their size
Humans increase speed mostly by increasing stride length
Long (relative to body size) legs in humans, H. erectus. Chimps short. Australopithecis?
Oscillating long legs is costly unless minimize moment of inertia, hence small human feet
Human feet small compared to chimps & pithecines (9% v 14% leg mass, hmn v chmp)
Bramble & Lieberman (2004) Nature 432: 345-352.
Skeletal strengthRunning: large skeletal stresses
Force at heel strike = 3-4X body wt
Force travels up skeleton
AdaptationsLarger lower limb joint surfaces in human v chimp, even after adjust for weight: knee, hip, sacroiliac, lumbar centra
Reduced femoral neck length & inter-acetabular distance reduces bending moments on femoral neck, sacrum, lower back – compare Homo to chimps, Australopithicus
Bramble & Lieberman (2004) Nature 432: 345-352.
StabilizationGluteus max: its “increased size is among the most distinctive of all human features”
Enlarged sacral transverse process
Enlarged area for erector spinae attachment on sacrum, PSIS – allows the forward pitch of trunk during running
Decoupled head & shoulder (longer neck, fewer/smaller muscles) Homo vs Pan, Austr
StabilizationReduced forearm mass in Homo (50% smaller than Pan when adjust for body weight) reduces effort to keep arm flexed
Decoupled head & shoulder (longer neck, fewer/smaller muscles) Homo vs chimp, Austr
Wide shoulders of Homo enhance counter-balancing effect of arm-swinging in running
Head StabilizationOccipital projection behind condyles improves balance, reduces pitch-forward tendency at footstrike
Larger relative diam of posterior semicircular canal increaes sensitivity to sagital plane accelerations of head
Large nucchal ligament seen in humans, cursors, & large-headed mammals (elephant) but not chimps; Australopithicus lacks nucchal line on occipital bone
ThermoregulationDissipate waste heat of running
Humans: Larger & more eccrine sweat glands for evaporative cooling
Lack of body hair
Larger near-surface cranial venous circulation
Mouth breathing (also lowers work of breathing)
Summary of some human adaptations for running
Fz(t)=vertical ground reaction force. Δvcom=change in velocity of center of mass. T=impact duration, g=gravitational acceleration.
Lieberman, Davis, et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Figure 1. Vertical ground reaction forces and foot kinematics for three foot strikes at 3.5m/s in the same runner. a, RFS during barefoot heel–toe running; b, RFS during shod heel–toe running; c, FFS during barefoot toe–heel–toe running. Both RFS gaits generate an impact transient, but shoes slow the transient’s rate of loading and lower its magnitude. FFS generates no impact transient even in the barefoot condition.
Lieberman, Davis, et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Figure 1. Vertical ground reaction forces and foot kinematics for three foot strikes at 3.5m/s in the same runner. a, RFS during barefoot heel–toe running; b, RFS during shod heel–toe running; c, FFS during barefoot toe–heel–toe running. Both RFS gaits generate an impact transient, but shoes slow the transient’s rate of loading and lower its magnitude. FFS generates no impact transient even in the barefoot condition.
Lieberman, Davis, et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Figure 1. Vertical ground reaction forces and foot kinematics for three foot strikes at 3.5m/s in the same runner. a, RFS during barefoot heel–toe running; b, RFS during shod heel–toe running; c, FFS during barefoot toe–heel–toe running. Both RFS gaits generate an impact transient, but shoes slow the transient’s rate of loading and lower its magnitude. FFS generates no impact transient even in the barefoot condition.
Lieberman, Davis, et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Figure 2. Variation in impact transients. a, Magnitude of impact transient in units of body weight for habitually shod runners who RFS (group 1; open boxes) and habitually barefoot runners who FFS when barefoot (group 3; shaded boxes).
Figure 2. Variation in impact transients. b, Rate of loading of impact transient in units of body weight for habitually shod runners who RFS (group 1; open boxes) and habitually barefoot runners who FFS when barefoot (group 3; shaded boxes).
Fz(t)=vertical ground reaction force. Δvcom=change in velocity of center of mass. T=impact duration, g=gravitational acceleration.
Lieberman, Davis, et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Effective mass during impact
Effective mass during impact, meas. & pred.
Open box=RFS barefoot; closed box=FFS barefoot; solid line=infinitely stiff ankle, dotted, infinitely compliant ankle. Str.idx.= location of impact cop as fraction of foot length.
Fig. 2. Vertical ground reaction force of a shod RFS, MFS, and FFS. Note the distinct impact peak of the RFS that is missing in the MFS and FFS patterns. RFS, rearfoot strikers; MFS, midfoot strikers; FFS, forefoot strikers.Altman, Davis (2012). Barefoot Running: Biomechanics andImplications for Running Injuries. Curr Sports Med Rep 11: 244-249.
Fig. 3. Vertical ground reaction force of a shod rearfoot striker (RFS) and a barefoot runner (BF). Note the similarity between the forefoot (Fig. 2) and barefoot curves.Altman, Davis (2012). Barefoot Running: Biomechanics andImplications for Running Injuries. Curr Sports Med Rep 11: 244-249.
Fig. 4. Eversion (pronation) moment (curved arrow) during barefoot (A) and shod (B) running, created from the vertical ground reaction force at landing. The eversion moment is higher in the shod condition (B) due to the larger moment arm resulting from the increased width of the shoe and heel flare.Altman, Davis (2012). Barefoot Running: Biomechanics and Implications for Running Injuries. Curr Sports Med Rep 11: 244-249.
Axial T1-weighted, fat-suppressed, magnetic resonance imaging (MRI) showing marrow edema and stress reaction of the entire left second metatarsal with soft tissue edema in a 19-year-old runner who newly adopted barefoot-simulating footwear for 3 to 4 weeks. Patient was successfully treated with protected weight bearing and modified activity.Hsu (2012). Barefoot Running Review. Foot & Ankle Int. 33: 787-794.