Effect of muscle mass and intensity of isometric contraction on heart rate

• Published in: Journal of applied physiology (1985) 2000-02, Vol.88 (2), p.487-492
• Main Authors: Galvez, Jose M, Alonso, Juan P, Sangrador, Luis A, Navarro, Gonzalo
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Biological and medical sciences; Double-Blind Method; Exercise; Fundamental and applied biological sciences. Psychology; Hand Strength - physiology; Heart; Heart Rate - physiology; Humans; Isometric Contraction - physiology; Linear Models; Male; Muscle, Skeletal - anatomy & histology; Muscle, Skeletal - physiology; Muscular system; Organ Size; Physical Exertion - physiology; Space life sciences; Striated muscle. Tendons; Time Factors; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2000.88.2.487

1  Instituto de Ergonomía MAPFRE SA, 50639 Zaragoza; 2  Diputación General de Aragón, 50004 Zaragoza; 3  Centro Nacional de Epidemiología, 28029 Madrid; and 4  Hospital Reina Sofía, 31500 Tudela, Navarra, Spain The purpose of this study was to determine the effect of muscle mass and the level of force on the contraction-induced rise in heart rate. We conducted an experimental study in a sample of 28 healthy men between 20 and 30 yr of age (power: 95%, : 5%). Smokers, obese subjects, and those who performed regular physical activity over a certain amount of energetic expenditure were excluded from the study. The participants exerted two types of isometric contractions: handgrip and turning a 40-cm-diameter wheel. Both were sustained to exhaustion at 20 and 50% of maximal force. Twenty-five subjects finished the experiment. Heart rate increased a mean of 15.1 beats/min [95% confidence interval (CI): 5.5-24.6] from 20 to 50% handgrip contractions, and 20.7 beats/min (95% CI: 11.9-29.5) from 20 to 50% wheel-turn contractions. Heart rate also increased a mean of 13.3 beats/min (95% CI: 10.4-16.1) from handgrip to wheel-turn contractions at 20% maximal force, and 18.9 beats/min (95% CI: 9.8-28.0) from handgrip to wheel-turn contractions at 50% maximal force. We conclude that the magnitude of the heart rate increase during isometric exercise is related to the intensity of the contraction and the mass of the contracted muscle. skeletal muscle; exercise; maximal force; muscle endurance