Project in brief
The overall goal is to maintain or even improve important aspects of physical performance, without injuring skeletal muscle connective tissue in space travelers on long-haul missions in Orbit. High-load flywheel resistance exercise (RE) training reduces or even counteracts muscle and strength loss, seen after 90 d bed rest (BR). It is unknown if this intervention concurrently stimulates the connective tissue of unloaded muscle. Considered being the weakest link of skeletal muscle, it appears connective tissue calls for relatively more time to adapt to increased load than the contractile elements. Concurrent BR/spaceflight and exercise training may induce conflicting signals, resulting in adaptation or blunting of the catabolic muscle response. Twenty-one healthy men, age 21-46 yr, are subjected to 6° head-down-tilt BR for 90 d, with or without RE. Coupled maximal concentric and eccentric actions are performed in the Supine Squat (4 sets of 7 reps) and Calf Press (4 x 14), every third day employing gravity-independent YoYo™ technology. Prior to, and following BR or BR+RE, biopsies are taken from mm. vastus lateralis and soleus. Expression of markers for collagen turnover and growth factors, involved in collagen turnover, are analyzed. More specifically changes in activation state of pathways regulating connective tissue integrity, are explored.
Because connective tissue may be the weak link leading to overload symptoms upon unaccustomed reloading, this study will disclose whether RE, using hardware designed for in-flight use, can blunt loss of skeletal muscle connective tissue, and thus strength during prolonged BR. The project will provide information important in designing exercise protocol guidelines for astronauts on extended missions in Orbit, and the general population as well.
Our overarching research focus is to determine the effects of prolonged reduced activity on connective tissue turnover in muscle and tendons induced by e.g., disuse, disease, spaceflight or aging.
Research in the field
- Moerch L, Pingel J, Boesen M, Kjaer M, Langberg H. The effect of acute exercise on collagen turnover in human tendons: influence of prior immobilization period. Eur J Appl Physiol Jul 13 [Epub ahead of print], 2012.
- Nedergaard A, Jespersen JG, Pingel J, Christensen B, Sroczynski N, Langberg H, Kjaer M, Schjerling P. Effects of 2 weeks lower limb immobilization and two separate rehabilitation regimens on gastrocnemius muscle protein turnover signaling and normalization genes. BMC Res Notes 28:166, 2012.
- Christensen B, Dyrberg E, Aagaard P, Kjaer M, Langberg H. Short-term immobilization and recovery affect skeletal muscle but not collagen tissue turnover in humans. J Appl Physiol 105: 1845-1851, 2008.
- Christensen B, Dyrberg E, Aagaard P, Enehjelm S, Krogsgaard M, Kjær M, Langberg H. Effects of long-term immobilization and recovery on human triceps surae and collagen turnover in the Achilles tendon in patients with healing ankle fracture. J Appl Physiol 105:420-426, 2008.