Hip but not thigh intramuscular adipose tissue is associated with poor balance and increased temporal gait variability in older adults

Abstract

Background: Intramuscular adipose tissue (IMAT) of the lower extremity is a strong negative predictor of mobility function. Variability in temporal gait factors is another important predictor of mobility function. The purpose of this study was to examine the relationships between IMAT in the hip and thigh muscles, balance, and temporal gait variability in older adults.

Methods: Forty-eight healthy community dwelling older adults (74 +/- 1 year) underwent a CT scan to quantify IMAT in the gluteus maximus (Gmax), gluteus medius/minimus (Gmed/min), hamstrings, vastus lateralis, and adductor muscles. Temporal Gait measures were collected on a GAITRite walkway and gait variability was determined by calculating intraindividual standard deviations. Individuals were divided by tertiles of temporal gait variability into categories of high, medium, and low variability. Differences in the IMAT of the hip abductors were calculated for those with high and low gait variability and partial correlations for gait variability and all muscle composition measures were determined for all variables with normalized gait speed as a covariate.

Results: Gmed/min IMAT was greater in those with higher gait variability compared to those with lower gait variability (p<0.05). Gmed/min IMAT was related to stride width variability (r=0.30, p<0.05). Gmax IMAT was also related to time variability of swing (r=0.42), stance (r=0.26), double limb support (r=0.43), double support loading (r=0.44), and double support unloading (r=0.50) (all p<0.05).

Conclusion: Increased IMAT in the proximal hip muscles, particularly the hip abductors, was associated with increased gait variability and poorer balance. These findings may have implications for the assessment and treatment of balance and falls such that interventions for enhancing balance and mobility among older individuals should take into account the importance of gluteal muscle composition.

Fig. (1)

A comparison of muscle composition of the gluteal muscles (Gluteus maximus and Gluteus medius/minimus) in those with high and low gait variability. HDL (high density lean) is a measure of the % of lean tissue and both LDL (low density lean) and mFAT (muscle fat) are measures of the % IMAT. Gait variability was determined by adding the z-scores for stride time, stance time, swing time, and double support time, high and low variability represent those in the high and low tertiles for variability. *=p<0.05.

Fig. (2)

Schematic diagram illustrating how IMAT may be related to increased gait variability and falls in older adults. Disease, obesity, injury, age and inactivity may all contribute to increased IMAT levels in skeletal muscle. High levels of IMAT may result in impaired muscle strength, activation and muscle quality which may result in increased levels of gait variability and increased fall risk.