Voluntary contractile rate of torque development in healthy 50-70 year old women: Measurement of, association with functional tasks and response to intervention.

This study aimed to measure contractile rate of torque development (RTD) from maximal voluntary isometric contractions (MVC) of the knee extensors and flexors in order to determine reliability of the measure, report age-related difference in RTD, determine the association between RTD and selected functional tasks and determine the effect of progressive resistance training (PRT) on RTD in healthy 50-70y women. 136 women performed MVC’s of the knee extensors and flexors. Maximal RTD was determined from the slope of the most linear phase of the torque-time trace. RTD was also determined at 0-50 ms; 0-100 ms and 0-200 ms from the onset of contraction in a subsample (n=26) of knee extensor MVC’s. Functional capability was determined based on the ability to complete a 900 m gait speed test (n=128) and the number of chair rises completed in 30 seconds (n=68). 57 participants were randomised into a protein supplementation (PRO) control group or a PRO + PRT group for 12 weeks. Maximal RTD had a coefficient of variance of ≤ 17%. RTD became more dependent on maximal strength as the time from the onset of contraction increased as did its association with maximal RTD. On average, participants in the 7th decade of life had a lower (~23%; P<0.01) RTD than their younger counterparts in the 6th decade. RTD had a weak association with extended gait speed (r=-0.234; P=0.008) and was not associated with chair rise performance (r=0.076; P=0.540). RTD did not change in response to 12 weeks of PRT and PRO compared to a PRO only group (+9% vs. +13%; P>0.05). Maximal RTD cannot be measured reliably in healthy 50-70 year old women from the most linear slope of the torque-time trace of an isometric MVC. Age-related difference in maximal RTD appears to be greater than that of maximal strength. Maximal RTD has a weak association with functional capability and does not change in response to PRT in healthy 50-70 year old women.

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