News & Views from the Editor-in-Chief - L. Bruce Gladden
As usual, I have identified three excellent articles among many in this month’s issue. First, Bowser and Roles conducted the first known study to compare running kinematics and kinetics between healthy weight and overweight/obese children. Their results indicate that overweight/obese children run with shorter steps, decreased hip and knee flexion excursions during early stance, higher ground reaction forces, and greater joint moments. These differences indicate that overweight/obese children exhibit a more rigid running pattern. Subsequently, overweight/obese children likely experience greater joint loading during running that could potentially result in lower extremity mal-alignments and other potential joint pathologies. Encouraging participation in physical activity is crucial in reducing childhood obesity rates. Equally important is prescribing appropriate exercises and progressions that avoid placing overweight/obese children at an increased risk for developing injuries or pathologies associated with excessive loading.
Next, passive static stretching is accompanied by an acute reduction in the force-generating capacity of the stretched muscle and perhaps even the contralateral homologous muscle. Accordingly, Coratella et al. investigated the acute effects of unilateral passive stretching on neuromuscular mechanisms involved in contralateral force-generating capacity. Before and after intermittent passive stretching, they assessed maximum voluntary contraction (MVC) and electrically evoked V-wave, H-reflex, and M-wave to reflect the supraspinal, spinal, and peripheral contribution, respectively, in both the stretched and the contralateral limb. They observed a reduction in the contralateral MVC accompanied by a decrease in the V-wave/M-wave ratio, while both H-reflex/M-wave ratio and M-wave remained unchanged. The authors concluded that only supraspinal mechanisms may be involved in contralateral MVC loss, albeit spinal correlates cannot be excluded. Peripheral mechanisms seem to play no role. These results offer a deeper insight into passive stretch effects on contralateral force-generating capacity.
Finally, regular exercise increases total daily energy expenditure; however, it usually results in less weight loss than expected. Broskey and colleagues designed the E-MECHANIC Ancillary study to assess how two common exercise doses; one for general health and the other for weight loss affects the different components of energy expenditure. This novel study combined the doubly labeled water method with a 24-hour indirect calorimetry measurement in a whole-room respiratory chamber. Individuals randomized to the high exercise dose lost only half of the expected amount of weight. Total daily energy expenditure increased slightly due to the exercise, but there was also a reduction in energy expenditure due to increased sedentary time. Thereby, the net contribution of exercise to daily energy expenditure was small. Exercise does not promote weight loss in all people as energy burned in exercise may be compensated by overall energy conservation.
L. Bruce Gladden
School of Kinesiology