Effects of age/gender profiles and physical activity level on symmetry of lumbar muscle activation in pain-free older adults during various spinal movements.

The study was cross-sectional and included pain-free adults, so it cannot show that muscle asymmetry causes low back pain. The sample was small and recruited by convenience sampling, so it may not represent adults with back pain, frailty, or different activity levels. Participants moved at their own pace, and speed and range of motion were not controlled, so differences in movement style may have affected muscle activation. Physical activity and sitting time were self-reported, which can be inaccurate. EMG was normalized to quiet standing, and the paper notes that low baseline activity can inflate normalized values. Only L3 paraspinal muscles were measured, so other trunk muscles were not assessed.

The paper reports NIH extramural research support. The supplied text does not include a conflicts-of-interest declaration.

Do not read these results as proof that left-side muscle asymmetry causes low back pain or that reducing sitting will prevent it. The study was cross-sectional, included pain-free older adults, and found associations only.