October 2017 - Volume 49 - Issue 10

  • L. Bruce Gladden, PhD, FACSM
  • 0195-9131
  • 1530-0315
  • 12 issues / year
  • 6/81 in Sports Sciences
  • 4.141
​​​​​​​​​​​​​​​​​​​​​​Three unique papers from different study areas are highlighted in this month's journal. First, Janz and colleagues analyzed 14 years of prospective data from the Iowa Bone Development Study and determined the contributions of sedentary time, light physical activity (PA), moderate to vigorous physical activity (MVPA), and TV viewing to total adiposity and, uniquely, to visceral adiposity. The same youths were followed from age 5 to age 19 years. MVPA, but neither light PA nor sedentary time, predicted adiposity throughout childhood and adolescence. Subjectively measured TV viewing was also a predictor of adiposity, independently of MVPA. Given that TV viewing, but not total sedentary time, was important, it seems likely that TV viewing represents more than just low energy expenditure; it may also represent uncontrolled snacking, extended eating patterns, unhealthy food preferences, and/or sleep disturbances. These results argue for focusing public health approaches on MVPA and reduction of TV viewing time.

Next, Healy and colleagues showed novel evidence that long-term reductions in sitting may have some benefit for indicators of cardiometabolic health among office workers. The activity changes achieved with their workplace-delivered intervention (largely the replacement of sitting with standing) seemed to produce benefits in "healthy" workers, mostly by mitigating the natural worsening in cardiometabolic risk biomarkers over time. The authors argue that long-term facilitation of movement and standing at work may be a useful approach to reducing cardiovascular disease risk in the working population, and note that workers at high risk for cardiovascular disease may particularly benefit from such interventions.

Finally, in a completely different avenue of research, several studies have reported that dietary nitrate improves exercise efficiency in humans, but the exact mechanisms of action remain unclear, especially since the majority of mechanistic research has been done in rodent models. Whitfield et al. sought to determine how nitrate supplementation in the form of beetroot juice might alter contractile function in human skeletal muscle. Beetroot juice increased force production during low-frequency transcutaneous electrical stimulation, indicative of an intrinsic intramuscular improvement. However, in contrast to previous work in rodent muscle, this occurred in the absence of a change in protein expression of targets associated with calcium handling. Further work is therefore required to determine the underlying causes of nitrate effects in humans, something that may be relevant for applications in both athletic and clinical populations.​

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L. Bruce Gladden

School of Kinesiology
Auburn University

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