Muscle-Specific Substrate Use During Cycle Exercise at 1 G: Implications for Astronaut Muscle Health
Lester BE, Standley RA, Lee JD, Fink WJ, Trappe SW, Trappe TA. Muscle-specific substrate use during cycle exercise at 1 G: implications for astronaut muscle health. Aviat Space Environ Med 2013; 84:789–96.
Introduction: Studies of real and simulated microgravity exposure show the lower limb muscles atrophy to the greatest extent, with the calf muscles being most affected and most difficult to target with exercise countermeasures. This ground-based study examined the metabolic involvement of the thigh and calf muscles during two cycle exercise protocols (moderate and high intensity) central to the exercise countermeasures program on the International Space Station. Methods: Intramuscular glycogen and triglyceride levels were quantified in the vastus lateralis and soleus muscles before and after a moderate (current ISS prescription: 45 min at 55% o2max, 131 ± 12 W) and high (proposed ISS prescription: 8 × 30-s intervals at 150% o2max, 459 ± 34 W) intensity
cycle exercise bout in nine individuals.
Results:
During moderate intensity cycling, glycogen was significantly reduced in the vastus lateralis (114 ± 27 mmol · kg−1 dry weight) and remained unchanged in the soleus. High intensity cycling significantly
reduced glycogen in both muscles, but the vastus lateralis (151 ± 25 mmol · kg−1 dry weight) used significantly more (∼160%) than the soleus (59 ± 11 mmol · kg−1 dry weight). Intramuscular triglycerides were unchanged in both
muscles at both intensities.
Discussion:
These findings, coupled with other ground-based studies, provide strong support for high intensity cycling being a more appropriate component of the ISS prescription for upper and lower leg skeletal muscle health and cardiorespiratory
fitness, although additional exercise paradigms that target the calf are warranted. These muscle-specific findings should be considered when designing exercise strategies for combating conditions of sarcopenia and muscle wasting on Earth.
Introduction: Studies of real and simulated microgravity exposure show the lower limb muscles atrophy to the greatest extent, with the calf muscles being most affected and most difficult to target with exercise countermeasures. This ground-based study examined the metabolic involvement of the thigh and calf muscles during two cycle exercise protocols (moderate and high intensity) central to the exercise countermeasures program on the International Space Station. Methods: Intramuscular glycogen and triglyceride levels were quantified in the vastus lateralis and soleus muscles before and after a moderate (current ISS prescription: 45 min at 55%
Keywords: glycogen; high intensity exercise; intramuscular triglycerides; sarcopenia
Document Type: Research Article
Publication date: 01 August 2013
- The peer-reviewed monthly journal, Aviation, Space, and Environmental Medicine (ASEM) provides contact with physicians, life scientists, bioengineers, and medical specialists working in both basic medical research and in its clinical applications. It is the most used and cited journal in its field. ASEM is distributed to more than 80 nations.
To access volumes 86 to present, please click here. - Information for Authors
- Submit a Paper
- Subscribe to this Title
- Membership Information
- Information for Advertisers
- Submit Articles
- Ingenta Connect is not responsible for the content or availability of external websites
- Access Key
- Free content
- Partial Free content
- New content
- Open access content
- Partial Open access content
- Subscribed content
- Partial Subscribed content
- Free trial content