Muscle and Tendon Contributions to Reduced Rate of Torque Development in Healthy Older Males.

Jonathan I Quinlan,John Lund,John P Williams,Nathaniel J Szewczyk,Martino V Franchi,Kenneth Smith,Bethan E Phillips,Catherine Boereboom,Philip J Atherton,Constantinos N Maganaris,Paul L Greenhaff,James I Blackwell,Marco V Narici

doi:10.1093/gerona/glx149

Abstract

BackgroundThe ability to rapidly generate and transfer muscle force is essential for effective corrective movements in order to prevent a fall. The aim of this study was to establish the muscle and tendon contributions to differences in rate of torque development (RTD) between younger (YM) and older males (OM).MethodTwenty-eight young males (23.9 years ± 1.1) and 22 old males (68.5 years ± 0.5) were recruited for assessment of Quadriceps Anatomical CSA (ACSA), maximal voluntary contraction (MVC), rate of torque development (RTD), and tendon biomechanical properties. Activation capacity (AC), maximal muscle twitch df/dt) and time to peak EMG amplitude (TTPE) were also assessed.ResultsAbsolute RTD (aRTD) was lower in OM (577.5 ± 34.6 Nm/s vs 881.7 ± 45.6 Nm/s, p < .0001). RTD remained lower in OM following normalization (nRTD) for muscle ACSA (9.93 ± 0.7 Nm/s/cm2 vs 11.9 ± 0.6 Nm/s/cm2, p < .05). Maximal muscle twitch df/dt (1,086 Nm∙s−1 vs 2,209 Nm∙s−1, p < .0001), TTPE (109.2 ± 8.6ms vs 154.6 ± 16.6 ms, p < .05), and AC (75.8 ± 1.5% vs 80.1 ± 0.9%, p < .01) were all affected in OM. Tendon stiffness was found to be lower in OM (1,222 ± 78.4 N/mm vs 1,771 ± 154.1 N/mm, p < .004). nRTD was significantly correlated with tendon stiffness (R2 = .15).ConclusionThese observations provide evidence that in absolute terms, a lower RTD in the elderly adults is caused by slower muscle contraction speeds, slower TTPE, reduced ACSA, reduced MVC, and a decrease in tendon stiffness. Once the RTD is normalized to quadriceps ACSA, only MVC and tendon stiffness remain influential. This strongly reinforces the importance of both muscle and tendon characteristics when considering RTD.

Highlights

The ability to rapidly generate and transfer muscle force is essential for effective corrective movements in order to prevent a fall
The age-related reduction in rate of torque development (RTD) was maintained after normalization of RTD to peak anatomical cross sectional area (CSA) (ACSA) (Figure 2) (11.9 ± 0.64 Nm∙s−1∙cm2 vs 9.93 ± 0.77 Nm∙s−1∙cm2, p < .05)
This study aimed to identify the origin of age-related differences in the rate of torque development in healthy older individuals

Summary

Introduction

The ability to rapidly generate and transfer muscle force is essential for effective corrective movements in order to prevent a fall. Method: Twenty-eight young males (23.9 years ± 1.1) and 22 old males (68.5 years ± 0.5) were recruited for assessment of Quadriceps Anatomical CSA (ACSA), maximal voluntary contraction (MVC), rate of torque development (RTD), and tendon biomechanical properties. RTD remained lower in OM following normalization (nRTD) for muscle ACSA (9.93 ± 0.7 Nm/s/cm vs 11.9 ± 0.6 Nm/s/cm, p < .05). Conclusion: These observations provide evidence that in absolute terms, a lower RTD in the elderly adults is caused by slower muscle contraction speeds, slower TTPE, reduced ACSA, reduced MVC, and a decrease in tendon stiffness. Once the RTD is normalized to quadriceps ACSA, only MVC and tendon stiffness remain influential. This strongly reinforces the importance of both muscle and tendon characteristics when considering RTD

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