Jeanne D. Johnston

Lower-Leg Compression, Running Mechanics, and Economy in Trained Distance Runners

The efficacy of and mechanisms behind the widespread use of lower-leg compression as an ergogenic aid to improve running performance are unknown. The purpose of this study was to examine whether wearing graduated lower-leg compression sleeves during exercise evokes changes in running economy (RE), perhaps due to altered gait mechanics. Sixteen highly trained male distance runners completed 2 separate RE tests during a single laboratory session, including a randomized-treatment trial of graduated calf-compression sleeves (CS; 15-20 mm Hg) and a control trial (CON) without compression sleeves. RE was determined by measuring oxygen consumption at 3 constant submaximal speeds of 233, 268, and 300 m/min on a treadmill. Running mechanics were measured during the last 30 s of each 4-min stage of the RE test via wireless triaxial 10-g accelerometer devices attached to the top of each shoe. Ground-contact time, swing time, step frequency, and step length were determined from accelerometric output corresponding to foot-strike and toe-off events. Gait variability was calculated as the standard deviation of a given gait variable for an individual during the last 30 s of each stage. There were no differences in VO2 or kinematic variables between CON and CS trials at any of the speeds. Wearing lower-leg compression does not alter the energetics of running at submaximal speeds through changes in running mechanics or other means. However, it appears that the individual response to wearing lower-leg compression varies greatly and warrants further examination.

Innovation in Weight Loss Intervention Programs: An Examination of a 3D Virtual World Approach

Obesity is a costly condition that can reduce quality of life and increase the risk for many serious chronic diseases and premature death. The rising rates, high prevalence, and adverse consequences of obesity call for the development and testing of new and innovative approaches that address weight loss barriers and bring help to those most affected by obesity. In this article, we examine the effectiveness of a 12-week behavioral-based weight loss program delivered via a 3D virtual world, Club One IslandTM (COI) in Linden Labs Second Life. Intervention design was informed by social cognitive theory and emerging research on avatar identification and the Proteus Effect. Our results offer strong preliminary evidence that not only can a 3D VW-based program be as effective as a content similar in-person intervention relative to positive biometric changes, but it may serve as a more effective platform to influence meaningful behavioral changes and increased self-efficacy.

Change in Physical Activity and Sitting Time After Myocardial Infarction and Mortality Among Postmenopausal Women in the Women's Health Initiative‐Observational Study

Background How physical activity (PA) and sitting time may change after first myocardial infarction (MI) and the association with mortality in postmenopausal women is unknown. Methods and Results Participants included postmenopausal women in the Womens Health Initiative‐Observational Study, aged 50 to 79 years who experienced a clinical MI during the study. This analysis included 856 women who had adequate data on PA exposure and 533 women for sitting time exposures. Sitting time was self‐reported at baseline, year 3, and year 6. Self‐reported PA was reported at baseline through year 8. Change in PA and sitting time were calculated as the difference between the cumulative average immediately following MI and the cumulative average immediately preceding MI. The 4 categories of change were: maintained low, decreased, increased, and maintained high. The cut points were ≥7.5 metabolic equivalent of task hours/week versus <7.5 metabolic equivalent of task hours/week for PA and ≥8 h/day versus <8 h/day for sitting time. Cox proportional hazard models estimated hazard ratios and 95% CIs for all‐cause, coronary heart disease, and cardiovascular disease mortality. Compared with women who maintained low PA (referent), the risk of all‐cause mortality was: 0.54 (0.34–0.86) for increased PA and 0.52 (0.36–0.73) for maintained high PA. Women who had pre‐MI levels of sitting time <8 h/day, every 1 h/day increase in sitting time was associated with a 9% increased risk (hazard ratio=1.09, 95% CI: 1.01, 1.19) of all‐cause mortality. Conclusions Meeting the recommended PA guidelines pre‐ and post‐MI may have a protective role against mortality in postmenopausal women.

Association of physical activity and sitting time with incident colorectal cancer in postmenopausal women

Findings from epidemiological studies have found that physical activity (PA) is associated with a lower risk of colorectal cancer (CRC). Recent studies have found an increased CRC risk with higher sitting time (ST); however, many studies did not include PA as a potential confounder. The objective of this project was to investigate the independent and combined associations of ST and PA with the risk of incident CRC, specifically colon and rectal cancer. Participants in the Women’s Health Initiative Observational Study (n=74 870), 50–79 years of age self-reported ST and PA at baseline, years 3 and 6. Incident CRC was the primary outcome; colon and rectal cancers were the secondary outcomes, which were centrally adjudicated. Over a 13-year follow-up period, 1145 incident cases of CRC were documented. A positive age-adjusted association was found between higher ST (≥10 vs. <5 h/day) and CRC (P for trend=0.04) and colon cancer (P for trend=0.05); however, these associations were attenuated and no longer significant in multivariable-adjusted models. Compared with inactive women (⩽1.7 MET-h/week), the multivariable risk of CRC in the high PA (>20 MET-h/week) group was 0.81 (95% confidence interval: 0.66–1.00; P for trend 0.04). Compared with inactive women with high ST (≥10 h/day), there was a trend toward reduced multivariable CRC risks with higher PA irrespective of ST level (interaction=0.64). We observed an inverse association between leisure time PA and the risk of CRC, particularly for rectal cancer. There was no association between ST and CRC in multivariable models.