Hypertrophic Response of Aged Women to Resistance Training is Positively Impacted by Participation in a Long‐Term Stretching Intervention

The loss of muscle mass and strength that occurs with advanced age, or sarcopenia, is a growing public health concern that impacts a growing portion of the population. The portion of the population over the age of 65 accounts for almost 20% of the total population. Muscle mass and strength are highly correlated with quality of life for aged adults. Mass is also a strong predictors of all‐cause mortality. Thus, resistance training (RT) is commonly recommended for aged adults. However, studies that have had young and aged adults perform the same percentage based RT program found that young adults gain significantly more strength and muscle mass than the aged adults. There are many levels of the hypertrophic response to RT that may be impaired resulting in the observed attenuation. However, similar attenuations have been observed following acute exercise making it possible that the impairment lies in the mechanotransduction cascade. One possible mechanism for decreased mechanotransduction is decreased mechanosensation caused by increased extracellular matrix stiffening. Stretching has been shown to decrease muscle stiffness in young men which indicates that this may be a viable means to modulate stiffness and improve the response to RT in aged adults. Objective The purpose of this study was to test the hypothesis that participation of aged adults in a stretching intervention (SI) prior to beginning RT will improve response to RT. The variables used to determine response to RT for this study are changes in isokinetic plantarflexor torque and volume of the medial and lateral gastrocnemius. Methods The participants for this study were 8 healthy young women in the RT only group (20.4±1.2 yr), 8 healthy aged women in the SI + RT group (74.1±6.2 yr) and 8 healthy aged women in the RT only group (73.8±4.5 yr). Participants in the aged SI + RT group participated in an SI 3 days a week for 8 weeks. Following the SI they participated in a lower extremity RT program 3 days a week for 8 weeks. The other two groups participated in only the RT. Both before and after the RT intervention plantarflexor strength and gastrocnemius muscle volume were measured. Results Following the RT intervention the young RT only and aged SI + RT groups both had significant increases in their plantarflexor torque production of 45% and 32%, respectively (p=0.002 and p=0.005). There was a 5% non‐significant change in the plantarflexor torque of the aged RT only group (p=0.41). There was a significant increase (11%) in the muscle volume of the aged SI + RT group following RT (p=0.02). The young RT only group showed a trend for increased muscle volume (p=0.09) with a 3% increase, but no change (0%) was detected in the aged RT only group (p=0.45). Conclusions Based on these data, having aged adults participated in a long‐term stretching intervention prior to completing a RT intervention significantly improves their response to the RT. The most important finding of this study is the increase in muscle volume in the aged SI + RT group. Studies have previously shown strength gains in aged groups, but often there is no accompanying increase in muscle size. With the link between muscle mass and mortality this finding should be explored further as the implications could have a lasting impact on the aging population. Support or Funding Information This work was supported by the American Society of Biomechanics by way of a graduate student Grant‐In‐Aid awarded to JEH.