Intramuscular Fat Influences Neuromuscular Activation of the Gluteus Medius in Older Adults

Abstract

The amount of tissue between the muscle and surface electromyography (sEMG) electrode influences the sEMG signals. Increased intramuscular adipose tissue (IMAT) of the hip abductor muscles negatively impacts balance in older individuals, but it is unknown if this is related to the ability to activate the muscles. The aim of this preliminary study was to investigate the influence of gluteus medius (GM) IMAT on sEMG amplitude during maximal voluntary isometric contractions (MVIC) of the hip abductors in older adults. We recruited 12 healthy community-dwelling older adults that underwent a spiral computerized tomography scan. High density lean (HDL), IMAT, and subcutaneous adipose tissue (SUBFAT) cross-sectional area of the GM were assessed. sEMG signal from the GM was recorded while participants performed an MVIC of the hip abductors. There was a negative correlation between GM activation and IMAT (r = −0.58, P = 0.046), and also SUBFAT (r = −0.78, P = 0.002) and a positive correlation with HDL (r = 0.73, P = 0.006). When controlling for SUBFAT, the partial correlations demonstrated a consistent negative correlation between GM activation and IMAT (r = −0.60, P = 0.050) but no relationship with HDL. The current results are important for helping to interpret the results from sEMG by accounting for IMAT. In conclusion, the neuromuscular activation of the GM may be reduced by the quantity of IMAT.

Hip Abductor and Adductor Rate of Torque Development and Muscle Activation, but Not Muscle Size, Are Associated With Functional Performance

“…Larger muscles have constantly showed to influence sprint (Miller et al, 2020) and jump performance (Alegre et al, 2009). However, no relationship was found between muscle size and the weight shifting phase preceding a step (Lanza et al, 2020b). It is important to notice the weight shifting phase is a stabilizing activity, while the sprint and jumping are performance tasks, which may explain the differences in muscle size contribution among tasks.…”

“…All participants were recruited from a single metropolitan region. The sample size for the bivariate correlation was calculated by the software GPower (version 3.1;Faul et al, 2007), and the following inputs were used: (a) Tails (two); (b) correlation p H1 (0.6, based on the average R 2 from significant correlations from a previous study; Lanza et al, 2020b)…”

“…The handheld dynamometer recorded the signal at 40 Hz, and the signal was exported to a computer using specific software (HHD/MMT download tool, Lafayette, IN, United States). RTD was measured across epochs of 50, 100, 200, and 300 ms (RTD 50 , RTD 100 , RTD 200 , and RTD 300 , respectively) from torque onset to the respective time and was divided by the duration of the epoch (e.g., torque at 50 ms/0.05 s) as previously used (Lanza et al, 2020b). RTD was normalized by the peak torque (MVT) achieved during the same contraction, and an average value was calculated for the three contractions for hip abduction and hip abduction.…”

“…The ability to quickly produce torque is essential for better jumping (McErlain-Naylor et al, 2014) and sprinting performance (Maćkała et al, 2015). Additionally, quickly producing torque during the first moments of the contraction (up to the first 300 ms from contraction onset) appears to be critical for successfully performing daily tasks such as stepping (Lanza et al, 2020b) and ascending stairs (Orssatto et al, 2020). Orssatto et al (2020) found that the knee extensors rate of torque development (RTD, 0-200 ms) explained 20% of the variance during an ascending stairs test in older adults, while other studies showed that hip abductors and adductors RTD (0-100, 0-150, and 0-200 ms) explained up to 53% of the variance of the weight transfer preceding a step in older adults (Lanza et al, 2020a,b).…”

“…Also, rapidly activating the muscles (e.g., rate of activation, RoA) to stabilize the movement appears critical to physical function. For instance, higher RoA of the tensor fascia latae (TFL) and adductor magnus results in a shorter time to shift weight before initiating a step in older adults (Lanza et al, 2020b). Moreover, muscle size along with neuromuscular activation, also explain physical function.…”