Load-sensitive adhesion factor expression in the elderly with skiing: relation to fiber type and muscle strength

Abstract

We hypothesized that 3-months of downhill skiing mitigates functional deficits of knee extensor muscles in elderly subjects due to specific recruitment of fast motor units during forceful turns on the slope. Downhill skiing lead to a 1.4-fold increase in mean cross sectional area of slow (p=0.04) and fast (p=0.08) type muscle fibres. Fold changes in the structural component of focal adhesions, gamma-vinculin, correlated with alterations in concentric force (r=0.64). Hypertrophy of fast fibres was more important in women than in men (1.7 vs. 1.1). Gender specific structural-functional adjustments of extensor muscle and attached patellar tendon were reflected by altered expression of pro- vs. de-adhesive proteins and a number of correlations. The de-adhesive protein tenascin-C was selectively increased in women compared to men (1.7 vs. 1.1) while the content of the adhesive collagen XII was specifically reduced by 39% in women. The pro-adhesive focal adhesion kinase showed a specific increase in men (1.9 vs. 1.1). Our findings identify that quantitatively matched adaptations in slow and fast motor units underlie the preventive effect of skiing against sarcopenia and support that hypertrophy and reinforcement of fibre adhesion in extensor muscle are two myocellular strategies which operate in the improvement of muscle strength.