Energetics and muscle-tendon function in gait Neil J. Cronin - PowerPoint PPT Presentation

Energetics and muscle-tendon function in gait Neil J. Cronin Neuromuscular Research Centre, University of Jyväskylä, Finland

1. Humans are excellent walkers

Humans ‘choose’ economical speed / SR Bramble & Lieberman, 2004 Nature Umberger & Martin, 2007 JEB

Human walking is comparatively economical McNeill Alexander, 2005 JEB

Human walking is mechanically economical Minimal muscle work Elastic tendon Lichtwark & Wilson, 2006 JEB Roberts & Azizi, 2011 JEB

→ → 4 months ‘rest’ → 2. Humans are excellent runners “His bpm…he monitor”. 7 marathons, 7 days, 7 continents (at the age of 59)

Humans also ‘choose’ the optimal running SR Normalised metabolic cost (% cost at preferred) Normalised stride rate (% preferred) Snyder & Farley, 2011 JEB

Human running is metabolically economical Bramble & Lieberman, 2004 Nature

Human running is comparatively economical Rubenson et al., 2007 JEB

Human running is mechanically economical Muscle 1 Running stride 4.5 km/h Muscle force Tendon 6.3 km/h 2.7 km/h 7.2 km/h Gastrocnemius Shortening velocity Lichtwark et al., 2007 J Biomech Farris & Sawicki, 2012 Proc Natl Acad

Human running is mechanically economical Muscle 7.2 km/h 1 Running stride 4.5 km/h Muscle force Tendon 6.3 km/h 2.7 km/h 7.2 km/h Gastrocnemius Shortening velocity Lichtwark et al., 2007 J Biomech Farris & Sawicki, 2012 Proc Natl Acad

3. Humans are terrible race walkers America’s

Race walking: A human invention Race walking speed ’ Normal ’ walking speed Bramble & Lieberman, 2004 Nature

Race walking is metabolically costly Data from 4 olympic race walkers 300 280 Race walking Walking 260 240 220 COT (ml O 2 / kg / km) 200 Running 180 160 140 120 100 0 5 10 15 20 25 Speed (km/h) Menier & Pugh, 1968 J Physiol

Race walking is energetically costly Cronin et al., 2016 JAP.

Race walking is mechanically costly MTU length Fascicle velocity Run MG 2 0 -2 10 km/h Racewalk Race Fast Racewalk 10 km/h Run walk Fast Run -4 Soleus 2 0 -2 -4 0 10 20 30 40 50 60 70 80 90 100 Cronin et al., 2016 JAP. Stride cycle (%)

Tak ake e ho home me me messages sages 1. We are economical walkers and can cover extremely long distances at relatively low cost. 2. We are economical runners , even compared to other species. 3. Humans did not evolve to race walk . Even after decades of training, race walking is uneconomical.

neil.j.cronin@jyu.fi