Influence of aging on isometric muscle strength,fat-free mass and electromyographic signal power of the upper and lower limbs in women

Background

Aging is a multifactorial process that leads to changes in the quantity andquality of skeletal muscle and contributes to decreased levels of musclestrength.

Objective

This study sought to investigate whether the isometric muscle strength,fat-free mass (FFM) and power of the electromyographic (EMG) signal of theupper and lower limbs of women are similarly affected by aging.

Method

The sample consisted of 63 women, who were subdivided into three groups(young (YO) n=33, 24.7±3.5 years; middle age (MA) n=15, 58.6±4.2 years; andolder adults (OA). n=15, 72.0±4.2 years). Isometric strength was recordedsimultaneously with the capture of the electrical activity of the flexormuscles of the fingers and the vastus lateralis during handgrip and kneeextension tests, respectively. FFM was assessed using dual-energy X-rayabsorptiometry.

Results

The handgrip strength measurements were similar among groups (p=0.523),whereas the FFM of the upper limbs was lower in group OA compared to groupYO (p=0.108). The RMSn values of the hand flexors were similar among groups(p=0.754). However, the strength of the knee extensors, the FFM of the lowerlimbs and the RMSn values of the vastus lateralis were lower in groups MA(p=0.014, p=0.006 and p=0.013, respectively) and OA (p=0.000, p=0.000 andp<0.000, respectively) compared to group YO.

Conclusions

The results of this study demonstrate that changes in isometric musclestrength in MLG and electromyographic activity of the lower limbs are morepronounced with the aging process of the upper limb.