A 10-Year Longitudinal Study of Muscle Morphology and Performance in Masters Sprinters

Abstract

Background: Both longitudinal and cross-sectional studies have demonstrated that muscle mass, strength and power are lost with ageing. Although longitudinal studies have shown changes in muscle morphology and function in sedentary, healthy active and endurance-trained older people, less is known about such age-related changes in sprint athletes. It has been proposed that active older people may provide a better study of healthy ageing not confounded by factors of inactivity and other unhealthy behaviours. Given that the training regimens of masters sprinters consist of strength and sprint training that elicit gains in muscle force, power and mass, sprinters may not suffer from measurable decrements in muscle strength, functional performance or morphology over a 10-year period.

Methods: To investigate this, m. vastus lateralis (VL) biopsies were taken from 24 masters sprinters aged 48-85 years at baseline and 10 years later. Immunofluorescent staining of slides taken from these biopsies was used to assess fibre type composition, fibre cross-sectional area (FCSA) and capillarisation. In addition, VL thickness was assessed using B-mode ultrasonography, maximum voluntary contraction (MVC) of knee extension was measured with an electromechanical dynamometer, and the flight time of a counter movement jump was determined with a contact matt. 60-m sprint times were measured using double-beam photocell gates connected to an electronic timer.

Results: FCSA, fibre-type composition, capillarisation and VL thickness had not changed significantly after 10 years. The decrease in jump power (-9.5% ± 5.7, p < 0.001) was attributable to a concomitant decrease in knee extension MVC (-21.0% ± 20.4, p < 0.001), not slowing of the muscle. Athletes demonstrated reduced 60-m sprint performance after 10 years (+14.2% increase in sprint time ± 12.4, p < 0.001) with greater loss in performance found in older participants (stepwise regression p < 0.004). Similarly, the loss of jump power found in the follow-up measurement (-9.47% ± 5.7, p < 0.001) was larger in the older participants (stepwise regression p < 0.001). However, no changes in muscle function or performance were significantly related to years of training or training volume.

Conclusions: Masters sprinters aged 48-85 maintained muscle histological characteristics over 10 years, but their training was unable to offset decrements in sprint performance and power that were attributable to a loss in force generating capacity, but not slowing of the muscle.

Keywords: MVC; ageing; atrophy; capillarisation; histology; masters athletes; muscle biopsy; performance; skeletal muscle; sprinters.

FIGURE 1

60‐m sprint time at baseline and 10 years later. Each colour and line indicate one individual.

FIGURE 2

Whole muscle function measures at baseline and 10 years later (10Y). For (a–c), each colour and line indicate one individual. (a) jump power, (b) maximum voluntary contraction of knee extension (MVC) and (c) jump velocity. (d) Velocity versus body mass/MVC (BM/MVC) at baseline and at 10Y.

FIGURE 3

Capillary indices in masters sprinters at baseline and 10 years later. Each colour and line indicate one individual. (a) Capillary‐to‐fibre ratio (C:F), (b) capillary density and (c) LogRSD (a measure of capillary spacing heterogeneity).

FIGURE 4

Histology of muscle biopsies. (a,b) Vastus lateralis muscle biopsy sections stained for Type I (red), Type IIa (green), Type IIx (unstained) and capillaries (green dots). (c) Mean fibre cross sectional area changes in masters sprinters at baseline and 10 years later. Each colour and line indicate one individual.

FIGURE 5

Sprint performance and jump power in masters sprinters. (a) 60‐m sprint time and jump power in individuals at baseline (blue, R ² = 0.616; p = 0.0001) and at the 10 year follow‐up (red, R ² = 0.444; p = 0.0026). (b) Percentage change in sprint time from baseline to 10‐year follow‐up (delta 60‐m sprint time) versus percentage change in jump power (delta power) (R ² = 0.349; p = 0.0099).