Lower energy cost of skeletal muscle contractions in older humans

Michael A. Tevald, Stephen A. Foulis, Ian R Lanza, Jane A. Kent-Braun

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Recent studies suggest that the cost of muscle contraction may be reduced in old age, which could be an important mediator of age-related differences in muscle fatigue under some circumstances. We used phosphorus magnetic resonance spectroscopy and electrically elicited contractions to examine the energetic cost of ankle dorsiflexion in 9 young (Y; 26 ± 3.8 yr; mean ± SD) and 9 older healthy men (O; 72 ± 4.6). We hypothesized that the energy cost of twitch and tetanic contractions would be lower in O and that this difference would be greater during tetanic contractions at f50 (frequency at 50% of peak force from force-frequency relationship) than at 25 Hz. The energy costs of a twitch (O = 0.13 ± 0.04 mM ATP/twitch, Y = 0.18 ± 0.06; P = 0.045) and a 60-s tetanus at 25 Hz (O = 1.5 ± 0.4 mM ATP/s, Y = 2.0 ± 0.2; P = 0.01) were 27% and 26% lower in O, respectively, while the respective force ·time integrals were not different. In contrast, energy cost during a 90-s tetanus at f50 (O = 10.9 ± 2.0 Hz, Y = 14.8 ± 2.1 Hz; P = 0.002) was 49% lower in O (1.0 ± 0.2 mM ATP/s) compared with Y (1.9 ± 0.2; P < 0.001). Y had greater force potentiation during the f50 protocol, which accounted for the greater age difference in energy cost at f50 compared with 25 Hz. These results provide novel evidence of an age-related difference in human contractile energy cost in vivo and suggest that intramuscular changes contribute to the lower cost of contraction in older muscle. This difference in energetics may provide an important mechanism for the enhanced fatigue resistance often observed in older individuals.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume298
Issue number3
DOIs
StatePublished - Mar 2010
Externally publishedYes

Fingerprint

Muscle Contraction
Skeletal Muscle
Costs and Cost Analysis
Adenosine Triphosphate
Tetanus
Muscle Fatigue
Ankle
Phosphorus
Fatigue
Magnetic Resonance Spectroscopy
Muscles

Keywords

  • ATP
  • Bioenergetics
  • Dorsiflexors
  • Force-frequency
  • Magnetic resonance
  • Twitch

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

Lower energy cost of skeletal muscle contractions in older humans. / Tevald, Michael A.; Foulis, Stephen A.; Lanza, Ian R; Kent-Braun, Jane A.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 298, No. 3, 03.2010.

Research output: Contribution to journalArticle

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abstract = "Recent studies suggest that the cost of muscle contraction may be reduced in old age, which could be an important mediator of age-related differences in muscle fatigue under some circumstances. We used phosphorus magnetic resonance spectroscopy and electrically elicited contractions to examine the energetic cost of ankle dorsiflexion in 9 young (Y; 26 ± 3.8 yr; mean ± SD) and 9 older healthy men (O; 72 ± 4.6). We hypothesized that the energy cost of twitch and tetanic contractions would be lower in O and that this difference would be greater during tetanic contractions at f50 (frequency at 50{\%} of peak force from force-frequency relationship) than at 25 Hz. The energy costs of a twitch (O = 0.13 ± 0.04 mM ATP/twitch, Y = 0.18 ± 0.06; P = 0.045) and a 60-s tetanus at 25 Hz (O = 1.5 ± 0.4 mM ATP/s, Y = 2.0 ± 0.2; P = 0.01) were 27{\%} and 26{\%} lower in O, respectively, while the respective force ·time integrals were not different. In contrast, energy cost during a 90-s tetanus at f50 (O = 10.9 ± 2.0 Hz, Y = 14.8 ± 2.1 Hz; P = 0.002) was 49{\%} lower in O (1.0 ± 0.2 mM ATP/s) compared with Y (1.9 ± 0.2; P < 0.001). Y had greater force potentiation during the f50 protocol, which accounted for the greater age difference in energy cost at f50 compared with 25 Hz. These results provide novel evidence of an age-related difference in human contractile energy cost in vivo and suggest that intramuscular changes contribute to the lower cost of contraction in older muscle. This difference in energetics may provide an important mechanism for the enhanced fatigue resistance often observed in older individuals.",
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