Proceedings of The Physiological Society

Ageing and Degeneration (Edinburgh, UK) (2015) Proc Physiol Soc 33, PC02

Poster Communications

Relationship between tendon stiffness and metabolic cost of walking in young and older adult humans

O. S. Mian1, G. L. Onambele2, L. P. Ardigo3, I. M. McEwan2, A. E. Minetti4, C. N. Maganaris5, M. V. Narici6

1. School of Applied Sciences, London South Bank University, London, United Kingdom. 2. Dept. of Exercise & Sport Science, Manchester Metropolitan University, Cheshire, United Kingdom. 3. School of Exercise & Sport Science, University of Verona, Verona, Italy. 4. Faculty of Medicine, University of Milan, Milan, Italy. 5. School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom. 6. Faculty of Medicine & Health Sciences, The University of Nottingham, Nottingham, United Kingdom.

Introduction: Tendon mechanical properties may affect metabolic cost of locomotion via influence on muscle efficiency (1) and elastic energy utilisation (2). Here, we examine whether there is a relationship between gastrocnemius tendon stiffness (TS) and metabolic cost of walking (CW) in young and older adults to explore whether age-related changes in TS (3) may contribute to age-related changes in CW (4). Methods: Participants were 15 young adults (YA; aged 18-40 years) and 20 older adults (OA; aged 60-77 years) recruited from the community. We had excluded any participants with diseases thought to influence gait or muscle function. Following familiarisation, participants walked on a treadmill at up to four different speeds (3, 4, 5, 6 km/hr; 5 min per speed). Oxygen uptake was measured using a portable system (Cosmed K4b2). Recordings in the final two minutes at each speed were used for analysis. CW was expressed as net (above standing) oxygen uptake per kg body mass per m travelled. On a separate occasion, Gastrocnemius TS was determined as previously described (5). Briefly, a slow ramp isometric plantar-flexion was performed with the knee at 180˚ and ankle at 90˚. Ankle torque (dynamometer) and tendon elongation (ultrasound imaging of gastrocnemius medialis myotendinous junction) were recorded synchronously. Tendon force was estimated using measured tendon moment arm, and by accounting for synergist and antagonist contributions to torque (5). TS was estimated using the tangent of a curve fitted to tendon elongation plotted against tendon force. The tangent was at 207 N (maximum voluntary contraction force in the weakest participant). Differences between groups were assessed using independent sample t-tests. Correlations were assessed using Pearson's r. Data are expressed as mean ± SD. TS, but not CW, data from this study have been published previously (5). Results: Averaged across speeds, CW (ml/kg/m) was 30% higher (p < .01) in OA (0.152 ± 0.031) than in YA (0.116 ± 0.016). TS (N/mm) was 41% lower (p < .01) in OA (30 ± 14) than in YA (51 ± 29). There was no significant correlation between TS & CW at any walking speed when YA & OA were combined into a single group (r = - 0.07 to -0.18; p > .22) or when OA was considered alone (r = -0.18 to -0.25; p > .31). In YA, there was a significant positive correlation between TS and CW at 3 km/hr (r = 0.52; p = .047) but not at the three faster speeds (r = 0.37 to 0.42; p > .12). Conclusion: These data do not support a significant link between gastrocnemius TS and CW within the range encountered across healthy young and older adult humans. Hence a decreased TS alone does not seem to account for increased CW in old age.

Where applicable, experiments conform with Society ethical requirements