Latest News & Research: 26 February 2019

Evening exercise won’t ruin sleep and may reduce appetite • Exercise may improve health by increasing gut bacterial diversity • Drop and give me 41!

Evening exercise won’t ruin sleep and may reduce appetite

New Australian research published in Experimental Physiology has suggested that 30 minutes of high-intensity exercise performed in the early evening does not negatively affect subsequent sleep, and may also reduce feelings of hunger.

Researchers at Charles Sturt University, NSW, recruited eleven middle-aged men to complete three experimental trials to investigate sleep and appetite responses to exercise performed in the morning (6 – 7am), afternoon (2 – 4pm) and evening (7 – 9pm). Participants were required to perform high-intensity cycling involving six one-minute, maximal intensity sprints interspersed by four minutes of rest. Blood collections were taken prior to exercise and following exercise to examine appetite-related hormones, and multiple tests were performed during sleep to assess sleep stages.

The results not only showed that evening exercise did not have a detrimental impact on subsequent sleep, but also that afternoon and evening high-intensity exercise were associated with greater reductions of the hunger stimulating hormone, ghrelin. It is important to note that a single bout of exercise was not linked to reduced hunger, but nevertheless, the observations from this study support high-intensity exercise early in the evening as a viable time-of day for exercise.

As this study’s sample size was relatively small, the findings extrapolated to other population groups beyond middle-aged men may be limited, given that sleep and appetite regulation are influenced by sex and age.

Penelope Larsen, lead author of the study, commented said: ‘In the future, we hope to conduct similar studies recruiting women, to determine whether sleep and appetite responses may be different depending on sex. Also, this study only considered a single bout of exercise; therefore, it would be beneficial to investigate long-term sleep and appetite adaptations to high-intensity exercise training performed either in the morning, afternoon or evening.’

‘Interestingly, power output during the sprint efforts was higher for the afternoon and evening trials compared to the morning trial, indicating that participants were able to perform better during latter parts of the day. Therefore, time-of-day may also need to be considered when planning training schedules.’

Source: The Physiological Society

Exercise may improve health by increasing gut bacterial diversity

Research published in Experimental Physiology has suggested that the efficiency with which we transport oxygen to our tissues (cardiorespiratory fitness) is a far greater predictor of gut microbiota diversity than either body fat percentage or general physical activity.

The findings suggest that exercise at a sufficiently high intensity to improve cardiorespiratory fitness may support health through favourable alterations in the presence, activity and clustering of gut microbes. Before now, it was understood that higher cardiorespiratory fitness tended to coincide with greater gut microbiota diversity, but it was unclear whether this relationship was attributable to body fat percentage or physical activities of daily-living.

Since cancer treatment is known to trigger physiological changes detrimental to cardio-metabolic health, including increased body fat percentage and declining cardiorespiratory fitness, this research was performed on cancer survivors. In total, 37 non-metastatic breast cancer survivors, who had completed treatment at least one year prior, were enrolled.

Participants performed a graded exercise test to estimate peak cardiorespiratory fitness, assessments of total energy expenditure and examination of gut microbiota from faecal swipes. The results showed that participants with the higher cardiorespiratory fitness had significantly greater gut microbiota diversity compared to less fit participants. Further statistical analyses highlighted that cardiorespiratory fitness accounted for roughly a quarter of the variance in species richness and evenness, independent of body fat percent.

The participant sample was restricted to women with a history of breast cancer, who tended to exhibit low cardiorespiratory fitness and other health problems, meaning generalisation to other groups should be made with caution.

Source: The Physiological Society

Drop and give me 41!

A US study published in JAMA Network Open has found that active, middle-aged men able to complete more than 40 push-ups had a significantly lower risk of cardiovascular disease (CVD) outcomes, including diagnoses of coronary artery disease and major events such as heart failure, during 10 years of follow-up compared with those who were able to do less than 10 push-ups during the baseline exam.

‘Our findings provide evidence that push-up capacity could be an easy, no-cost method to help assess cardiovascular disease risk in almost any setting. Surprisingly, push-up capacity was more strongly associated with cardiovascular disease risk than the results of submaximal treadmill tests’ said first author Justin Yang, occupational medicine resident in the Department of Environmental Health at Harvard T.H. Chan School of Public Health.

Objective assessments of physical fitness are considered strong predictors of health status; however, most current tools such as treadmill tests are too expensive and time-consuming to use during routine exams. This is the first known study to report an association between push-up capacity and subsequent cardiovascular disease outcomes.

The researchers analyzed health data from 1,104 active male firefighters collected from 2000 to 2010. Their mean age was 39.6 and mean body mass index (BMI) was 28.7. Participants’ push-up capacity and submaximal treadmill exercise tolerance were measured at the start of the study, and each man subsequently completed annual physical examinations and health and medical questionnaires.

During the 10-year study period, 37 CVD-related outcomes were reported. All but one occurred in men who completed 40 or fewer pushups during the baseline exam. The researchers calculated that men able to do more than 40 push-ups had a 96% reduced risk of CVD events compared with those who were able to do less than 10 push-ups. Push-up capacity was more strongly associated with lower incidence of cardiovascular disease events than was aerobic capacity as estimated by a submaximal treadmill exercise test.

Because the study population consisted of middle-aged, occupationally active men, the results may not be generalizable to women or to men of other ages or who are less active, note the authors.

‘This study emphasises the importance of physical fitness on health, and why clinicians should assess fitness during clinical encounters’ said senior author Stefanos Kales, professor in the Department of Environmental Health at Harvard Chan School and chief of occupational medicine at Cambridge Health Alliance.

Source: Harvard T H Chan school of Public Health