Change in Acute Response of Aged Women to Resistance Exercise Following a Long‐Duration Stretching Intervention
Authors: Hibbert Jamie E , Jones Terry E , Domire Zachary J 
Published: November 2023

Introduction

Sarcopenia, the age‐related loss of muscle mass and strength, is highly prevalent in the aged adult population. However, the mechanism for this phenomenon is not fully understood. It is commonly recommended that aged adults participate in resistance exercise training as a means of combatting sarcopenia, but a number of studies have shown that aged adults have an attenuated response to resistance training than young adults. One potential explanation is that with age skeletal muscle is less responsive to mechanical stimuli due to increased muscle stiffness. If less of the stimuli is being registered by the mechanoreceptors in the muscle tissue, the hypertrophic response to this activity will be diminished compared to the response in tissue without impaired mechanosensation.

Objective

The purpose of this study was to examine whether p70S6k phosphorylation induced by a single bout of lower extremity resistance exercise is attenuated in aged compared to young women within 30 minutes of the exercise, and whether this response would change in the aged group following participation in a stretching intervention (SI).

Methods

Sixteen healthy, female participants were recruited for this study. The participants were either in the young (24±3 yr, n=8) or the aged group (74±6 yr, n=8). Participants completed a single unilateral bout of resistance exercise to maximally engage the plantarflexors. Muscle biopsies were immediately collected bilaterally from the gastrocnemius. The aged group then took part in an 8‐week SI. Following the SI, they performed the same bout of unilateral resistance exercise and, again, bilateral muscle biopsies were collected. Western blot analyses were conducted to examine changes in p70S6k phosphorylation between the exercised and control limbs and differences in the aged group following the stretching intervention.

Results

After the initial acute bout of exercise the young adults showed a significant increase in the proportion of phosphorylated to total p70S6k (p=0.03) over the control limb. The aged adults showed no significant increase in the proportion of phosphorylated to total p70S6k over the control limb (p=0.13). Following the SI, there was a trend toward increasing response of the aged group to a single bout of resistance exercise (p=0.1). Additionally, following SI the response of the aged group was similar to the young group (Figure 1). The ratio pre‐SI was 1.99 in the aged group and changed to 2.83, more similar to that of the young group (2.97).

Conclusions

Based on these data, the response measured by p70S6k phosphorylation observed in the aged adults following the SI became more similar to the response observed in the young adults. While there was not a significant difference between the phosphorylation ratio of the aged adults from pre‐ to post‐intervention, the difference between the response of the young and old groups following exercise changed from being significantly different to statistically insignificant. This may indicate that stretching influenced a positive change in the response to a single bout of lower extremity exercise in the aged adults.

Support or Funding Information

This work was supported by The International Society of Biomechanics by way of a Matching Dissertation Grant awarded to JEH and by the American Society of Biomechanics by way of a graduate student Grant‐In‐Aid awarded to JEH.

This table shows the ratio of p‐p70S6k to total p70S6k in both the unexercised (control) limb and the exercised limb as well as the ratio comparing the two. All values are given as mean ± standard deviation.

Control Limb (p‐p70S6k/total)
Exercised Limb (p‐p70S6k/total)
Ratio (Exercised/Control)

Young
0.35±0.19
1.12±1.06
2.97±1.68

Old Pre
0.25±0.07
0.51±0.59
1.99±1.89

Old Post
0.32±0.30
0.58±0.63
2.83±3.27