Division of Medical Sciences and Graduate Entry Medicine, University of Nottingham, MRC-ARUK Centre for Musculoskeletal Ageing Research, Royal Derby Hospital, UK.
Faculty of Sciences, School of Sports and Exercise science, Liverpool John Moore's Univeristy, UK.
J Gerontol A Biol Sci Med Sci. 2018 Mar 14;73(4):539-545. doi: 10.1093/gerona/glx149.
The 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).
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. Activation capacity (AC), maximal muscle twitch df/dt) and time to peak EMG amplitude (TTPE) were also assessed.
Absolute 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).
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.
为了有效进行矫正运动以防止跌倒，快速产生和传递肌肉力量的能力至关重要。本研究的目的是确定年轻男性（YM）和老年男性（OM）之间在扭矩发展速率（RTD）上的差异中肌肉和肌腱的贡献。
招募了 28 名年轻男性（23.9 岁±1.1）和 22 名老年男性（68.5 岁±0.5）进行股四头肌解剖 CSA（ACSA）、最大自主收缩（MVC）、RTD 和肌腱生物力学特性的评估。还评估了激活能力（AC）、最大肌肉抽搐 df/dt）和肌电图幅度达峰时间（TTPE）。
OM 的绝对 RTD（aRTD）较低（577.5±34.6 Nm/s 与 881.7±45.6 Nm/s，p<.0001）。在肌肉 ACSA 归一化（nRTD）后，OM 的 RTD 仍然较低（9.93±0.7 Nm/s/cm2 与 11.9±0.6 Nm/s/cm2，p<.05）。最大肌肉抽搐 df/dt（1086 Nm∙s-1 与 2209 Nm∙s-1，p<.0001）、TTPE（109.2±8.6ms 与 154.6±16.6 ms，p<.05）和 AC（75.8±1.5% 与 80.1±0.9%，p<.01）在 OM 中均受到影响。还发现 OM 中的肌腱刚度较低（1222±78.4 N/mm 与 1771±154.1 N/mm，p<.004）。nRTD 与肌腱刚度显著相关（R2=0.15）。
这些观察结果表明，从绝对值来看，老年人的 RTD 较低是由于肌肉收缩速度较慢、TTPE 较慢、ACSA 减少、MVC 减少和肌腱刚度降低所致。当将 RTD 归一化为股四头肌 ACSA 时，只有 MVC 和肌腱刚度仍然有影响。这强烈地强调了在考虑 RTD 时肌肉和肌腱特性的重要性。
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