Mechanical and metabolic determination of V̇O2 and fatigue during repetitive isometric contractions in situ

Bill Ameredes, William F. Brechue, Wendell N. Stainsby

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (L(o)) or short length (L(s); ~0.9 · L(o)), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (L(o) vs. L(s), all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (P(o)) = 544 vs. 174 (0.38 · P(o)) g/g, maximal blood flow (Q̇) = 2.0 vs. 1.4 ml · min-1 · g-1, and maximal oxygen uptake (V̇O2) = 12 rs. 9 μmol · min-1 · g-1. Tension at L(o) decreased to 0.64 · P(o) over 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at L(s). In separate muscles contracting at L(o), Q̇ was set to that measured at L(s) (1.1 ml · min-1 · g-1), resulting in decreased V̇O2 (7μmol · min-1 · g-1), and rapid fatigue, to 0.44 · P(o). These data demonstrate that 1) muscles at L(o) have higher Q̇ and V̇O2 values than those at L(s); 2) fatigue occurs at L(o) with high V̇O2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at L, with lower tension, Q̇, and V̇O2 suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension and V̇O2 between L(o) and L(s) groups indicate that muscles contracting isometrically at initial lengths shorter than L(o) are working under submaximal conditions.

Original languageEnglish (US)
Pages (from-to)1909-1916
Number of pages8
JournalJournal of Applied Physiology
Volume84
Issue number6
StatePublished - Jun 1998
Externally publishedYes

Fingerprint

Isometric Contraction
Fatigue
Muscles
Skeletal Muscle
Canidae
Oxygen

Keywords

  • Blood flow
  • Canine
  • Gastrocnemius muscle
  • Length
  • Oxygen uptake
  • Passive tension
  • Preload

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Mechanical and metabolic determination of V̇O2 and fatigue during repetitive isometric contractions in situ. / Ameredes, Bill; Brechue, William F.; Stainsby, Wendell N.

In: Journal of Applied Physiology, Vol. 84, No. 6, 06.1998, p. 1909-1916.

Research output: Contribution to journalArticle

@article{0dfcdc3bb68e49c9b1371f500da5d328,
title = "Mechanical and metabolic determination of V̇O2 and fatigue during repetitive isometric contractions in situ",
abstract = "Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (L(o)) or short length (L(s); ~0.9 · L(o)), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (L(o) vs. L(s), all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (P(o)) = 544 vs. 174 (0.38 · P(o)) g/g, maximal blood flow (Q̇) = 2.0 vs. 1.4 ml · min-1 · g-1, and maximal oxygen uptake (V̇O2) = 12 rs. 9 μmol · min-1 · g-1. Tension at L(o) decreased to 0.64 · P(o) over 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at L(s). In separate muscles contracting at L(o), Q̇ was set to that measured at L(s) (1.1 ml · min-1 · g-1), resulting in decreased V̇O2 (7μmol · min-1 · g-1), and rapid fatigue, to 0.44 · P(o). These data demonstrate that 1) muscles at L(o) have higher Q̇ and V̇O2 values than those at L(s); 2) fatigue occurs at L(o) with high V̇O2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at L, with lower tension, Q̇, and V̇O2 suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension and V̇O2 between L(o) and L(s) groups indicate that muscles contracting isometrically at initial lengths shorter than L(o) are working under submaximal conditions.",
keywords = "Blood flow, Canine, Gastrocnemius muscle, Length, Oxygen uptake, Passive tension, Preload",
author = "Bill Ameredes and Brechue, {William F.} and Stainsby, {Wendell N.}",
year = "1998",
month = "6",
language = "English (US)",
volume = "84",
pages = "1909--1916",
journal = "Journal of Applied Physiology",
issn = "8750-7587",
publisher = "American Physiological Society",
number = "6",

}

TY - JOUR

T1 - Mechanical and metabolic determination of V̇O2 and fatigue during repetitive isometric contractions in situ

AU - Ameredes, Bill

AU - Brechue, William F.

AU - Stainsby, Wendell N.

PY - 1998/6

Y1 - 1998/6

N2 - Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (L(o)) or short length (L(s); ~0.9 · L(o)), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (L(o) vs. L(s), all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (P(o)) = 544 vs. 174 (0.38 · P(o)) g/g, maximal blood flow (Q̇) = 2.0 vs. 1.4 ml · min-1 · g-1, and maximal oxygen uptake (V̇O2) = 12 rs. 9 μmol · min-1 · g-1. Tension at L(o) decreased to 0.64 · P(o) over 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at L(s). In separate muscles contracting at L(o), Q̇ was set to that measured at L(s) (1.1 ml · min-1 · g-1), resulting in decreased V̇O2 (7μmol · min-1 · g-1), and rapid fatigue, to 0.44 · P(o). These data demonstrate that 1) muscles at L(o) have higher Q̇ and V̇O2 values than those at L(s); 2) fatigue occurs at L(o) with high V̇O2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at L, with lower tension, Q̇, and V̇O2 suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension and V̇O2 between L(o) and L(s) groups indicate that muscles contracting isometrically at initial lengths shorter than L(o) are working under submaximal conditions.

AB - Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (L(o)) or short length (L(s); ~0.9 · L(o)), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (L(o) vs. L(s), all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (P(o)) = 544 vs. 174 (0.38 · P(o)) g/g, maximal blood flow (Q̇) = 2.0 vs. 1.4 ml · min-1 · g-1, and maximal oxygen uptake (V̇O2) = 12 rs. 9 μmol · min-1 · g-1. Tension at L(o) decreased to 0.64 · P(o) over 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at L(s). In separate muscles contracting at L(o), Q̇ was set to that measured at L(s) (1.1 ml · min-1 · g-1), resulting in decreased V̇O2 (7μmol · min-1 · g-1), and rapid fatigue, to 0.44 · P(o). These data demonstrate that 1) muscles at L(o) have higher Q̇ and V̇O2 values than those at L(s); 2) fatigue occurs at L(o) with high V̇O2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at L, with lower tension, Q̇, and V̇O2 suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension and V̇O2 between L(o) and L(s) groups indicate that muscles contracting isometrically at initial lengths shorter than L(o) are working under submaximal conditions.

KW - Blood flow

KW - Canine

KW - Gastrocnemius muscle

KW - Length

KW - Oxygen uptake

KW - Passive tension

KW - Preload

UR - http://www.scopus.com/inward/record.url?scp=0031832032&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031832032&partnerID=8YFLogxK

M3 - Article

VL - 84

SP - 1909

EP - 1916

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 6

ER -