Abstract
BackgroundIt has been established that excellence in sports with short and long exercise duration requires a high proportion of fast-twitch (FT) or type-II fibers and slow-twitch (ST) or type-I fibers, respectively. Until today, the muscle biopsy method is still accepted as gold standard to measure muscle fiber type composition. Because of its invasive nature and high sampling variance, it would be useful to develop a non-invasive alternative.MethodologyEighty-three control subjects, 15 talented young track-and-field athletes, 51 elite athletes and 14 ex-athletes volunteered to participate in the current study. The carnosine content of all 163 subjects was measured in the gastrocnemius muscle by proton magnetic resonance spectroscopy (1H-MRS). Muscle biopsies for fiber typing were taken from 12 untrained males.Principal FindingsA significant positive correlation was found between muscle carnosine, measured by 1H-MRS, and percentage area occupied by type II fibers. Explosive athletes had ∼30% higher carnosine levels compared to a reference population, whereas it was ∼20% lower than normal in typical endurance athletes. Similar results were found in young talents and ex-athletes. When active elite runners were ranked according to their best running distance, a negative sigmoidal curve was found between logarithm of running distance and muscle carnosine.ConclusionsMuscle carnosine content shows a good reflection of the disciplines of elite track-and-field athletes and is able to distinguish between individual track running distances. The differences between endurance and sprint muscle types is also observed in young talents and former athletes, suggesting this characteristic is genetically determined and can be applied in early talent identification. This quick method provides a valid alternative for the muscle biopsy method. In addition, this technique may also contribute to the diagnosis and monitoring of many conditions and diseases that are characterized by an altered muscle fiber type composition.
Highlights
In mammals, including humans, skeletal muscle fibers exist in two main categories, the fatigue-resistant slow-twitch (ST) or type-I fibers, and the fatigue-sensitive fast-twitch (FT) or type-II fibers [1]
Muscle carnosine content shows a good reflection of the disciplines of elite track-and-field athletes and is able to distinguish between individual track running distances
The differences between endurance and sprint muscle types is observed in young talents and former athletes, suggesting this characteristic is genetically determined and can be applied in early talent identification. This quick method provides a valid alternative for the muscle biopsy method. This technique may contribute to the diagnosis and monitoring of many conditions and diseases that are characterized by an altered muscle fiber type composition
Summary
In mammals, including humans, skeletal muscle fibers exist in two main categories, the fatigue-resistant slow-twitch (ST) or type-I fibers, and the fatigue-sensitive fast-twitch (FT) or type-II fibers [1]. Classical papers from the 70s [2,3] established that excellence in sports with short and long exercise duration requires a high proportion of FT and ST muscle fibers, respectively. Measurement of the muscle fiber type composition can be a tool for talent identification and for defining an athlete’s optimal exercise duration in track-and-field as well as many other sports. Because of the invasive nature and high sampling variance of the muscle biopsy method, a non-invasive alternative to measure muscle fiber type composition would be useful. It has been established that excellence in sports with short and long exercise duration requires a high proportion of fast-twitch (FT) or type-II fibers and slow-twitch (ST) or type-I fibers, respectively. Because of its invasive nature and high sampling variance, it would be useful to develop a non-invasive alternative
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