Cycling efficiency is related to the percentage of Type I muscle fibers

E. F. Coyle, L. S. Sidossis, J. F. Horowitz, J. D. Beltz

Research output: Contribution to journalArticle

406 Citations (Scopus)

Abstract

We determined that the variability in the oxygen cost and thus the caloric expenditure of cycling at a given work rate (i.e., cycling economy) observed among highly endurance-trained cyclists (N = 19; mean ± SE; V̇O(2max), 4.9 ± 0.1 l · min-1; body weight, 71 ± 1 kg) is related to differences in their % Type I muscle fibers. The percentage of Type I and II muscle fibers was determined from biopsies of the vastus lateralis muscle that were histochemically stained for ATPase activity. When cycling a Monark ergometer at 80 RPM at work rates eliciting 52 ± 1, 61 ± 1, and 71 ± 1% V̇O(2max), efficiency was determined from the caloric expenditure responses (V̇O2 and RER using open circuit spirometry) to steady-state exercise. Gross efficiency (GE) was calculated as the ratio of work accomplished · min-1 to caloric expenditure · min-1, whereas delta efficiency (DE) was calculated as the slope of this relationship between approximately 50 and 70% V̇O(2max). The % Type I fibers ranged from 32 to 76%, and DE when cycling ranged from 18.3 to 25.6% in these subjects. The % Type I fibers was positively correlated with both DE (r = 0.85; P < 0.001; N = 19) and GE (r = 0.75; P < 0.001; N = 19) during cycling. Additionally, % Type I fibers was positively correlated with GE (r = 0.74; P < 0.001; N = 13) measured during the novel task of two-legged knee extension; performed at a velocity of 177 ± 6° · s-1 and intensity of 50 and 70% of peak V̇O2 for that activity. Therefore, the relationship between muscular efficiency and muscle fiber type is not specific to cycling. We conclude that muscular efficiency varies greatly in highly endurance- trained cyclists and most of this variability appears to be related to differences in their % Type I muscle fibers. Therefore, when endurance- trained men exercise under these conditions, Type I muscle fibers appear to be substantially more efficient than Type II muscle fibers, possibly as a result of a lower rate of ATP turnover as reflected by a lower V̇O2 while performing exercise at a given power output.

Original languageEnglish (US)
Pages (from-to)782-788
Number of pages7
JournalMedicine and Science in Sports and Exercise
Volume24
Issue number7
StatePublished - 1992
Externally publishedYes

Fingerprint

Slow-Twitch Muscle Fibers
Health Expenditures
Fast-Twitch Muscle Fibers
Exercise
Muscles
Spirometry
Quadriceps Muscle
Adenosine Triphosphatases
Knee
Adenosine Triphosphate
Body Weight
Oxygen
Biopsy
Costs and Cost Analysis

Keywords

  • FAST TWITCH
  • MECHANICAL EFFICIENCY
  • MUSCLE ENERGETICS
  • MUSCULATURE CONTRACTION
  • MYOSIN
  • PHYSICAL EXERCISE
  • SLOW TWITCH

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Coyle, E. F., Sidossis, L. S., Horowitz, J. F., & Beltz, J. D. (1992). Cycling efficiency is related to the percentage of Type I muscle fibers. Medicine and Science in Sports and Exercise, 24(7), 782-788.

Cycling efficiency is related to the percentage of Type I muscle fibers. / Coyle, E. F.; Sidossis, L. S.; Horowitz, J. F.; Beltz, J. D.

In: Medicine and Science in Sports and Exercise, Vol. 24, No. 7, 1992, p. 782-788.

Research output: Contribution to journalArticle

Coyle, EF, Sidossis, LS, Horowitz, JF & Beltz, JD 1992, 'Cycling efficiency is related to the percentage of Type I muscle fibers', Medicine and Science in Sports and Exercise, vol. 24, no. 7, pp. 782-788.
Coyle, E. F. ; Sidossis, L. S. ; Horowitz, J. F. ; Beltz, J. D. / Cycling efficiency is related to the percentage of Type I muscle fibers. In: Medicine and Science in Sports and Exercise. 1992 ; Vol. 24, No. 7. pp. 782-788.
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