The metabolic responses of human type I and II muscle fibres during maximal treadmill sprinting

• Published in: The Journal of physiology Vol. 478; no. Pt 1; pp. 149 - 155
• Main Authors: Greenhaff, P L, Nevill, M E, Soderlund, K, Bodin, K, Boobis, L H, Williams, C, Hultman, E
• Format: Journal Article
• Language: English
• Published: England The Physiological Society 01-07-1994
• Subjects: Adenosine Triphosphate - metabolism; Adult; Biopsy; Exercise Test; Female; Glycogen - metabolism; Humans; Hydrogen-Ion Concentration; Lactates - blood; Male; Muscles - cytology; Muscles - metabolism; Phosphocreatine - metabolism; Physical Exertion; Reference Values; Space life sciences; Time Factors
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1994.sp020238

1. Muscle biopsy samples were obtained from the vastus lateralis of six healthy volunteers before and after 30 s of treadmill
sprinting. A portion of each biopsy sample was used for mixed-fibre metabolite analysis. Single fibres were dissected from
the remaining portion of each biopsy and were used for ATP, phosphocreatine (PCr) and glycogen determination. 2. Before exercise,
PCr and glycogen contents were higher in type II fibres (79.3 +/- 2.7 and 472 +/- 35 mmol (kg dry matter (DM)-1, respectively)
compared with type I fibres (71.3 +/- 3.0 mmol (kg DM)-1, P < 0.01 and 375 +/- 25 mmol (kg DM)-1, P < 0.001, respectively).
3. Peak power output was 885 +/- 66 W and declined by 65 +/- 3% during exercise. Phosphocreatine and glycogen degradation
in type II fibres during exercise (74.3 +/- 2.5 and 126.3 +/- 15.8 mmol (kg DM)-1, respectively) was greater than the corresponding
degradation in type I fibres (59.1 +/- 2.9 mmol (kg DM)-1, P < 0.001 and 77.0 +/- 14.3 mmol (kg DM)-1, P < 0.01, respectively).
The decline in ATP during exercise was similar when comparing fibre types (P > 0.05). 4. Compared with previous studies involving
similar durations of maximal cycling exercise, isokinetic knee extension and intermittent isometric contraction, the rates
of substrate utilization recorded in type I fibres were extremely high, being close to the rapid rates observed in this fibre
type during intense contraction with limb blood flow occluded.