Research Highlights from the October Issue of the Journal Medicine & Science in Sports & Exercise

Breaks from Long Periods of Sitting Improves Blood Glucose Control, but Fat Tissue Dysfunction Remains

Population cross-sectional studies indicate that prolonged sitting has negative effects on multiple health outcomes. Yet, there has been little attempt to understand the physiology which might underlie or explain these associations. In this new study, investigators asked whether short bouts of physical activity (two minutes walking every 20 minutes over 5.5 hours) would improve metabolism in a group of eleven men and women with overweight and obesity (average age 50 years).

Results showed that continuously breaking prolonged sitting with short bouts of physical activity reduced blood glucose and insulin after eating–by approximately 50 percent! This is a very large effect and one that is clinically very meaningful. Despite these large and sustained differences in post-feeding glucose and insulin levels, fat tissue responses (the expression of key genes) were not affected. So, while breaks from prolonged sitting are highly effective for improving glucose control, this strategy does not, in the short term, translate into a beneficial physiological effect in adipose (fat) tissue. Longer-term studies are needed to understand whether these improvements in glucose control might bring about corresponding changes in adipose tissue over a period of weeks or months.

For more information, view the abstract or contact the investigator.

Maternal Physical Activity During Pregnancy and Offspring Liver Health

Maternal physical activity/exercise before and during pregnancy can have a positive impact on offspring health, but maternal consumption of a high-fat diet can have a negative impact on the offspring. To study these issues in an animal model, the investigators tested whether maternal physical activity could reduce or prevent the harmful effects of maternal high-fat diet feeding on liver health in male and female rat offspring. Maternal exercise was found to increase markers that indicate improved health in the liver mitochondria of the offspring (mitochondria are the energy powerhouse of the cell). The beneficial adaptations included increasing proteins that are responsible for making new mitochondria and removing old, damaged ones. In addition, female offspring were found to have elevated markers of liver mitochondria health, as compared to the males, possibly explaining why the females were protected against excess fat accumulation in the liver. These findings highlight the importance of engaging in physical activity prior to and during pregnancy and provide interesting insights into sex differences that collectively influence liver health.

For more information, view the abstract or contact the investigator.

Older Adults and Reduction in Post-exercise Pain Perception

In healthy younger adults, a single session of isometric exercise can temporarily decrease pain sensitivity and perception. Isometric exercises provide a helpful tool to study this phenomenon. Isometrics are those exercises that involve static contraction–force is applied by the muscle against an immovable object, but no muscle shortening occurs, e.g., squeezing a jar as hard as you can. This phenomenon of reduced pain sensitivity following acute isometric exercise is called “exercise-induced hypoalgesia.” In this study, the investigators assessed whether 52 healthy older adults would experience exercise-induced hypoalgesia after performing a single bout of isometric exercise with their hands and forearms. The researchers also measured the physical activity patterns of these subjects for one week, using an accelerometer. An accelerometer is a small device worn on the hip that measures how much a person moves and the intensity of those movements.

This study, which supports evidence from prior studies, showed that healthy older adults do not experience exercise-induced hypoalgesia. In other words, many older adults did not experience reduced pain sensitivity following a single session of isometric exercise, as is often found in younger adults. Interestingly, however, participants’ weekly physical activity behavior was important in predicting which older adults did experience reduced pain sensitivity following the exercise. Specifically, older adults who did more moderate to vigorous physical activity per week experienced greater exercise-induced hypoalgesia, meaning they experienced more reduction in pain following exercise. These results point to potential benefits of physical activity in maintaining older adults’ capacity for pain reduction following acute exercise. Understanding modifiable factors associated with age-related changes in pain processing, such as physical activity behavior, is essential to pain prevention and management strategies for this growing segment of the population.

For more information, view the abstract or contact the investigator.

Forget Whistling While You Work – Pedaling May Be Healthier

People who work in sedentary environments are inactive and have increased risks for obesity, diabetes and heart disease. Much of this increase in disease risk is due to the consequences of sedentary behaviors on decreasing the body’s sensitivity to insulin. Being physically active at work can be challenging and difficult to implement. Researchers at the University of Massachusetts compared a standard desk with a prototype pedal desk, which allows workers to sit and pedal at self-paced rates. Subjects were 12 sedentary overweight/obese male and female office workers. After giving subjects a test meal, blood levels for sugar (glucose), insulin and fats (fatty acids) were monitored. The subjects were given four sample computer-based work tasks to complete over two hours; everyone participated in both study conditions on different days–one with the standard desk and one with the pedal desk. Comparing results for the pedal desk to the standard desk, there were no changes in blood sugar or fat levels; there was also no difference in performances of the assigned work tasks. However, with the pedal desk conditions, the same sugar and fat levels were associated with much lower insulin levels. This means that use of the pedal desk allowed workers to use less insulin to achieve the same glucose and fat levels. Using less insulin to achieve the same effect typically indicates an improvement in the body’s sensitivity to insulin. Pedal desks may provide a viable option for sedentary workers to improve their metabolic health while maintaining their work performance.

For more information, view the abstract or contact the investigator.