Different muscle strategy during head/knee level of functional reaching-transporting task to decrease falling probability in postmenopausal women with osteoporosis

BACKGROUND: The reaching-transporting task as an essential daily activity impacts balance control and falling in older women. This study investigated the different muscle strategies during the head/knee level of the functional reaching-transporting task in postmenopausal women with osteoporosis. METHODS: 24 postmenopausal volunteers were classified into two groups based on the lumbar T-score: osteoporosis (≤ -2.5, n = 12) and non-osteoporosis (> –1, n = 12). Using a custom-designed device, participants randomly performed 12 reaching-transporting tasks at the head and knee levels. Electromyography signals were collected while reaching and transporting phases with a wireless system. The peak of the root means square (PRMS) and time to PRMS (TPRMS) were measured. In addition, the isometric muscle strength and the fear of falling were assessed. RESULTS: The isometric muscle strength in the osteoporotic group was significantly lower than in the non-osteoporotic group (P < 0.05), except for vastus lateralis (VL). The PRMS of VL, (P = 0.010) during the reaching phase and VL (P = 0.002) and gastrocnemius lateralis (GL) (P < 0.001) during transporting phase was greater than the non-osteoporotic group. The PRMS value of the muscles was greater for reaching-transporting at the knee level than the head level; this increase was significant just for VL and biceps femoris during the transporting phase (P = 0.036 and P = 0.004, respectively). CONCLUSION: Osteoporotic women have more muscle activities during the reaching-transporting task, especially at the knee level, compared to the head level. Their muscle weakness may lead to insufficient stability during the task and cause disturbance and falling, which requires further investigation.