News & Views from the Editor-in-Chief - L. Bruce Gladden
I am pleased to bring three papers to your particular attention in this month's journal. First, prior research has shown that older adults exhibit dysfunctional central pain modulatory processing compared to younger individuals, including a deficient capacity for exercise-induced hypoalgesia, a phenomenon in which pain sensitivity and pain perception to noxious stimulation is temporarily reduced following an acute bout of moderate to vigorous exercise. In this context, Ohlman et al. are the first to reveal that older adults who accumulate more moderate to vigorous physical activity per week experience greater exercise-induced hypoalgesia. These results point to potential benefits of physical activity in maintaining older adults' capacity for pain inhibition following acute exercise. Understanding modifiable factors associated with age-related dysfunctional central pain modulatory processing, such as physical activity behavior, is highly relevant to pain prevention and management strategies for this growing segment of the population.
Secondly, Ma and colleagues examined the regulatory effects of different intensities of exercise on the level and function of circulating endothelial progenitor cell-derived exosomes (EPC-EXs) in mice. They report that exercise elevated the plasma level of EPC-EXs and their microRNA-126 content in an intensity-dependent manner. Treatment of endothelial cells with circulating EPC-EXs isolated from moderately exercised mice provided anti-apoptotic and pro-angiogenic effects against high glucose and hypoxic injury. These beneficial effects were mediated by the activation of the microRNA-126 downstream proteins, SPRED1 and VEGF. Although exercise can increase the level of total exosomes in circulation, the cellular source has not been explored. These findings may offer a molecular mechanism for exercise-induced benefits on vascular diseases such as diabetes mellitus.
In my third highlight, Fukutani and Herzog studied residual force enhancement (RFE). The work/force achieved by muscles in the shortening phase of stretch-shortening cycles (SSCs) is greater when shortening is preceded by stretch. This property of skeletal muscle has been observed consistently. However, how this enhanced work/force is achieved remains unclear. Fukutani and Herzog tested the idea that RFE is partly responsible for the increased work/force output in SSCs. This aim was achieved by performing SSCs in which the stretch phase was kept constant while the magnitude of shortening was changed in single fibers of rabbit psoas. They found that RFE decreases with increasing shortening magnitudes in SSCs leading to the conclusion that while RFE contributes to the enhanced work/force in the shortening phase of SSCs, its effect diminishes with increasing shortening magnitudes.
L. Bruce Gladden
School of Kinesiology