Maximal Handgrip Force Research Articles

Sympathoadrenal-circulatory regulation during sustained isometric exercise in young and older men

The aim of this study was to test the hypothesis that the arterial blood pressure, vasoconstrictor, and sympathoadrenal adjustments to sustained submaximal isometric exercise become augmented with advancing age in humans. Fourteen young (26 +/- 1 yr) and 14 older (66 +/- 1 yr) healthy males performed isometric handgrip exercise at 30% of maximal voluntary force until exhaustion (inability to maintain target force). Maximal handgrip force was quite similar in the young and older subjects (402 +/- 20 vs. 392 +/- 20 N, respectively). The two groups did not differ significantly on any variable at rest. During sustained handgrip to exhaustion, peak levels of both perceived exertion and contracting forearm electromyographic activity were similar in the young and older men, suggesting equivalent voluntary efforts. Exercise time was not different in the two groups (315 +/- 27 s in young vs. 339 +/- 17 s in older men). Throughout exercise the increases in arterial blood pressure were very similar in the young and older subjects. Heart rate increased less (P less than 0.05), but stroke volume (impedance cardiography) tended to decrease less (not significant) in the older men; thus the increases in cardiac output were not different in the two groups. During the latter portion of exercise, systemic vascular resistance tended to increase in both the young and older men, with no significant group differences. The blood flow responses in the whole calf (venous occlusion plethysmography) and the calf skin (laser-Doppler velocimetry) were similar in the young and older subjects, as were the corresponding increases in vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory Muscle Strength in Congestive Heart Failure

In experimental animals, conditions which drastically decrease cardiac output may reduce the strength and endurance of respiratory muscles leading to hypercapnic respiratory failure. Because patients with chronic CHF have reduced cardiac output and vital capacity (FVC), we measured PImax and PEmax and maximal handgrip force in 16 patients with CHF and 18 AMNs. The patients with CHF had a mean left ventricular ejection fraction of 26 +/- 7 percent. Maximal respiratory pressures were significantly reduced; group mean values (+/- SD) for PImax at FRC were 41.4 +/- 5.6 cm H2O (CHF) and 102.1 +/- 27.4 cm H2O (AMN) (p less than 0.001), with PImax values in five patients with CHF as low as 20 to 30 cm H2O. In most patients, PEmax was comparably reduced. Handgrip force was less dramatically reduced, suggesting selective respiratory muscle weakness. Possible explanations include reduction in respiratory muscle blood flow or generalized muscular atrophy and weakness related to cardiac cachexia.

A microcomputer system for the measurement of finger forces

In the analysis of hand functions, the production and control of forces exerted during voluntary contraction of the finger muscles plays an important role; unfortunately such an analysis is rarely seen in routine clinical examinations of neurological patients. A microcomputer controlled system for the measurement and analysis of finger forces is described. The system consists of a modified Z80 based microcomputer, a commercially available high precision force transducer, a specially designed force signal amplifier and a suite of menu-driven user interactive programs. A variety of tasks is implemented by means of the computer programs. In addition to the measurement of maximum hand grip force, the system is able to record forces continuously as a function of time. Task characteristics and the type of feedback presented to the subject are under user control; they can be varied to meet clinical or experimental requirements. Examples of programs and clinical applications are presented and discussed.

Electromyographic study of muscular overflow during precision handgrip.

This study was designed to describe the "overflow" of muscular activity to muscles beyond the essential prime mover and synergists during a precision handgrip exercise. Five subjects performed a 10-minute isometric handgrip exercise consisting of one-second contractions alternated with one-second rests. Four different force levels were assigned: 5, 15, 25, and 40 percent of each subject's maximum handgrip force. All subjects demonstrated overflow activity at the 5-percent level, and three of the five subjects showed more overflow at the 5-percent level than at 15 percent. The greatest amount of overflow was shown at the 40-percent level. No striking interindividual or intraindividual consistency in recruitment order of overflow muscles was apparent. Two distinguishable types of overflow were observed: continuous overflow was the characteristic type at the lower force levels, whereas an interrupted pattern of overflow synchronized to the handgrip contraction was typical of the higher force levels. The possible effects of overflow on precision motor skills are discussed.

Vibration-induced decrease in the muscle force in lumberjacks.

Isometric maximal hand grip force was measured with a strain gauge dynamometer in 91 lumberjacks and 31 controls during a 2-min compression-relaxation task. Measurements were carried out on both hands with and without simultaneous vibration exposure. The muscle forces of older subjects were smaller than those of younger men, independent of occupational vibration exposure. The fatigue curves of lumberjacks and control subjects had the same shape. During vibration exposure in the test, the forces diminished in the left hand significantly in the lumberjacks but not in the control subjects. The force level of fatigue curves of the lumberjacks with a history of diminished grip force was lower and decreased more during vibration exposure than in the lumberjacks with a history of normal grip force. The reduction in the hand grip force during vibration exposure in the lumberjacks seemed to be linked to lesions in the peripheral nerves and to activation of a tonic vibration reflex, but probably not to circulation disturbances. The fatigue mechanism seemed to be the same in lumberjacks and control subjects.