TY - JOUR

T1 - Changes in mechanical properties of human plantar flexor muscles in ageing

AU - Ochala, Julien

AU - Lambertz, Daniel

AU - Pousson, Michel

AU - Goubel, Francis

AU - Van Hoecke, Jacques

PY - 2004/3

Y1 - 2004/3

N2 - Changes in contractile and elastic properties of human plantar flexor muscles in ageing, were investigated in 12 young (19-24 years, YG) and 11 old (61-74 year, OG) men. Maximal isometric and concentric voluntary torques, at several angular velocities, were measured to construct torque-angular velocity relationship. This led to the calculation of an index of maximal shorting velocity (VImax) at low torque. Two methods were then used to calculate musculotendinous (MT, quick-release movements) and musculoarticular (MA, sinusoidal perturbations) stiffness. In both cases, stiffness was linearly related to torque, leading to the calculation of a stiffness index (SI) as the slope of the stiffness-torque relationship: SIMT and SI MA, respectively. MA stiffness under passive conditions (K p) was also determined. Surface electromyograms were useful to control agonist and antagonist myoelectrical activities. As expected, maximal isometric (P<0.05) and concentric torques (P<0.05), as well as VI max(P<0.05) were lower in OG compared to YG. SIMT values were higher for OG compared to YG (P<0.05), leading to a mean difference of 55%, whereas SIMA and Kp were not significantly different between the two groups. Thus, older men were weaker and exhibited higher SIMT values. These impairments seem to be principally due to muscular atrophy and modifications in both muscle fibre-type distribution and fibre composition, in ageing. Invariance of SIMA and Kp would suggest an adaptive mechanism in articular structures to avoid the continuous integration of the ankle joint stiffness by the central nervous system, what may simplify most daily motor tasks.

AB - Changes in contractile and elastic properties of human plantar flexor muscles in ageing, were investigated in 12 young (19-24 years, YG) and 11 old (61-74 year, OG) men. Maximal isometric and concentric voluntary torques, at several angular velocities, were measured to construct torque-angular velocity relationship. This led to the calculation of an index of maximal shorting velocity (VImax) at low torque. Two methods were then used to calculate musculotendinous (MT, quick-release movements) and musculoarticular (MA, sinusoidal perturbations) stiffness. In both cases, stiffness was linearly related to torque, leading to the calculation of a stiffness index (SI) as the slope of the stiffness-torque relationship: SIMT and SI MA, respectively. MA stiffness under passive conditions (K p) was also determined. Surface electromyograms were useful to control agonist and antagonist myoelectrical activities. As expected, maximal isometric (P<0.05) and concentric torques (P<0.05), as well as VI max(P<0.05) were lower in OG compared to YG. SIMT values were higher for OG compared to YG (P<0.05), leading to a mean difference of 55%, whereas SIMA and Kp were not significantly different between the two groups. Thus, older men were weaker and exhibited higher SIMT values. These impairments seem to be principally due to muscular atrophy and modifications in both muscle fibre-type distribution and fibre composition, in ageing. Invariance of SIMA and Kp would suggest an adaptive mechanism in articular structures to avoid the continuous integration of the ankle joint stiffness by the central nervous system, what may simplify most daily motor tasks.

KW - Ageing

KW - Contractility

KW - Joint stiffness

KW - Musculotendinous stiffness

UR - http://www.scopus.com/inward/record.url?scp=1342286731&partnerID=8YFLogxK

U2 - 10.1016/j.exger.2003.11.004

DO - 10.1016/j.exger.2003.11.004

M3 - Journal article

C2 - 15036394

AN - SCOPUS:1342286731

VL - 39

SP - 349

EP - 358

JO - Experimental Gerontology

JF - Experimental Gerontology

SN - 0531-5565

IS - 3

ER -