Three articles particularly caught my eye in this month’s issue of MSSE: one on training to prevent deconditioning due to microgravity, one on the benefits of regular exercise to prevent sleep problems, and a third on the negative effects of increased sedentary time in a natural environment.
With long-term space missions planned for the future, optimal exercise training interventions will be critical for protecting astronaut health and maintaining high-level physical functioning. As physiological deconditioning occurs rapidly in a microgravity environment, effective exercise countermeasures are important for mitigating these changes. Cotter et al. gathered information on a novel device that permits concurrent aerobic and resistance training while meeting many of the equipment engineering constraints required for spaceflight. Overall, concurrent exercise was successful at positively manipulating cardiovascular and musculoskeletal conditioning during simulated microgravity. However, a significant problem remains: the soleus and plantar flexors were resistant to the training due to a heightened sensitivity to unloading.
In an entirely different research area, Dishman and colleagues followed 7,368 men and 1,155 women from the Aerobics Center Longitudinal Study, assessing cardiorespiratory fitness at four consecutive clinic visits at intervals of 2–3 years. After adjustment for other risk factors, each minute decline in treadmill endurance between ages 51 and 56 was associated with an increase in the odds of incident sleep complaints by 2% in men and 1% in women. Odds were approximately 8% higher per minute decline in people with sleep complaints at two or three visits. These results suggest that maintenance of cardiorespiratory fitness during middle age, when decline in fitness typically accelerates and risk of sleep problems is elevated, helps protect against the onset of sleep complaints made to a physician in both men and women.
Finally, on a third topic, Lyden et al. used an ecologically relevant model to study metabolic effects of sedentary behavior; that is, they studied participants in their natural environment where they significantly increased their daily sedentary time, but were allowed to take breaks from sedentary behaviors to accumulate small amounts of light-intensity, moderate-intensity, and vigorous-intensity activities. Three metrics of physical behavior (reduced time in light intensity activity, and increased time in sedentary bouts longer than 30 and 60 min) appeared to drive a negative association of increased sedentary time with reduced postprandial glucose and insulin metabolism. As a companion paper, I refer you to the highly cited paper of Powell and Blair [The public health burdens of sedentary living habits: theoretical but realistic estimates. Med Sci Sports Exerc. 1994;26(7):851-856].
L. Bruce Gladden