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.