Isometric Handgrip Task Research Articles

The Relationship between Muscle Fatigue and Recovery during Isometric Handgrip Task

The Relationship between Muscle Fatigue and Recovery during Isometric Handgrip Task

Complexity of force output during static exercise in individuals with Down syndrome

Force variability is greater in individuals with Down syndrome (DS) compared with persons without DS and is similar to that seen with normal aging. The purpose of this study was to examine the structure (in both time and frequency domains) of force output variability in persons with DS to determine whether deficits in force control are similar between individuals with DS and older adults. An isometric handgrip task at a constant force (30% of maximal voluntary contraction) was completed by individuals with DS (n = 29, age 26 yr), and healthy young (n = 26, age 27 yr) and older (n = 33, age 70 yr) individuals. Mean, standard deviation (SD), and coefficient of variation (CV) were used to analyze the magnitude of force output variability. Spectral analysis and approximate entropy (ApEn) were used to analyze the structure of force output variability. Mean force output for DS was lower than in young controls (P < 0.05) but no different from old controls. Individuals with DS had greater SD and CV than young and old controls (P < 0.05). The DS group had a significantly greater proportion of spectral power within the 0-to 4-Hz bandwidth than the young and older controls (P < 0.05). The DS group had significantly lower ApEn values than the young controls (P < 0.05), but there were no differences in ApEn between the DS group and the old controls (P > 0.05). In conclusion, young persons with DS demonstrate enhanced temporal structure and greater amplitude of low-frequency oscillations in the force output signal than age-matched non-DS peers. Interestingly, young persons with DS and older persons without DS have similar time-dependent structure of force output variability. This would suggest a possible link between premature aging and less complex force output in persons with DS.

The Effect of Manipulated Self-Efficacy on Perceived and Sustained Effort

Self-efficacy's role in determining perceived and sustained effort during an isometric handgrip task was assessed using a repeated measures experimental design. Moderately active, predominantly Caucasian, participants (male = 33, female = 39, M = 19.18 years, SD = .74) were recruited from the southeastern United States. Participants were randomly assigned to one of three groups: High-efficacy (HE), low-efficacy (LE), or control. Efficacy expectations were manipulated via false performance feedback. During the task participants provided differentiated ratings of perceived effort at 15-s intervals. Effort tolerance was determined by the length of time the participant could maintain the task. Repeated measures (RM) multivariate analysis of variance (MANOVA) indicated the HE group found the task less strenuous and more enjoyable than the LE or control group. Furthermore, the HE group demonstrated greater tolerance of the task than either the LE or control group. These findings imply that self-efficacy has a major role in enhancing performance and physical effort tolerance.

Attention focus during physical effort: The mediating role of task intensity

Objectives Tenenbaum's (2001) [A social-cognitive perspective of perceived exertion and exertion tolerance. In R. N. Singer, H. Hausenblas, & C. Janelle (Eds.), Handbook of sport psychology (pp. 810–820). New York, NY:Wiley] exercise intensity-attention linkage model was used to design and carry out two studies to examine individuals’ attentional strategies during engagement in two physically demanding tasks, and the mediating effect of task intensity on attention focus. Design An experimental design was employed where thought classifications (associative vs. dissociative) during three stages of a handgrip task (study 1) and during 50%, 70%, and 90% VO 2 max effort in a cycling task (study 2) were subjected to non-parametric Chi-square analysis. Methods Male and female participants were exposed to the increasing sensation of physical effort via two fatiguing tasks: an isometric handgrip task ( n=35), and a stationary cycling task ( n=13). During each task participants were instructed to vocally express their current thoughts—in sentences, phrases or words—continuously throughout the testing procedure. Participant's self-reported thoughts were recorded during the tasks, and later classified to reveal patterns of associative and dissociative attention focus. Results Attention focus was predominantly associative when task intensity was high. These findings are consistent with Tenenbaum's (2001) [A social-cognitive perspective of perceived exertion and exertion tolerance. In R. N. Singer, H. Hausenblas, & C. Janelle (Eds.), Handbook of sport psychology (pp. 810–820). New York, NY:Wiley] model postulating the relationship between exercise intensity and attention allocation, which maintains that above a given effort threshold physiological cues dominate attention focus. Conclusions During conditions of high workload and prolonged duration, attention is focused on overwhelming physiological sensations, which dominate focal awareness. At this point an associative attention focus is almost unavoidable.

Hemodynamic alterations in alcohol-related transitory hypertension

Alcoholic patients are often transiently hypertensive (tHT) during days 1–3 of withdrawal but become normotensive thereafter. However, at 3–4 weeks postwithdrawal these tHT patients may still show exaggerated blood pressure rises to isometric handgrip exercise. We examined the hemodynamic mechanisms associated with persistent altered pressure response. Forty-two alcoholic inpatients were equally divided into three subgroups based on admission BPs: transitory hypertensive (tHT; BP ≥ 160/95 mmHg), transitory borderline hypertensive (tBH; 140/90 ≤ BP < 160/95), and normotensive (NT; BP < 140/90). After 3–4 weeks of sobriety, the alcoholics and a normotensive nonalcoholic group (CONTs; n = 14) were tested during rest and an isometric handgrip task. Impedance cardiographic evaluation at both times showed elevated peripheral resistance, elevated heart rate, and reduced stroke volume in tHTs. Liquor consumption was found to be highly predictive of the altered hemodynamic and BP activity. Alcoholic patients with acute withdrawal hypertension (1–3 days) may show a persistent alteration of BP regulation even when resting pressures are normal.

Hemodynamic adjustments to laboratory stress: the influence of gender and personality.

Exaggerated cardiovascular reactivity to psychological stress is a potential pathophysiological mechanism linking behavior and cardiovascular disease. Because of the recognized gender differences in incidence of cardiovascular disease, potential gender differences in cardiovascular reactivity to laboratory stressors have been evaluated. The current study examined the cardiovascular responses of a total of 42 young women (N = 22) and men (N = 20) undergoing a laboratory protocol including the following: a nonverbal math task, a mirror tracing task, the Stroop Color-Word interference task, and an isometric handgrip task. In addition to the assessment of heart rate and blood pressure, cardiac output, stroke volume, total peripheral resistance and preejection period were assessed by impedance cardiography. A number of personality characteristics that vary in prevalence by gender were also measured to evaluate their ability to explain potential gender differences in cardiovascular responses. Results indicated that men responded with greater total peripheral resistance and systolic and diastolic blood pressure responses than did women on a subset of tasks, whereas women exhibited larger increases in heart rate on a subset of tasks. Thus, men were more likely to be "vascular" reactors, with women being more likely to be "cardiac" reactors. Personality characteristics did differ between men and women, but did not explain significant variance in the gender differences in cardiovascular responses. We conclude that additional studies should focus on experimental manipulations of potential physiological mechanisms responsible for these differences, such as reproductive hormones.

Cardiovascular responses to mental arithmetic and handgrip during different conditions of postural change.

ABSTRACTTwenty healthy male subjects, aged 18–29 yrs, were studied during three sequences of four different postural trials‐sitting, sitting to standing, standing, and standing to sitting. The first sequence was a baseline, without other stimulation. In the remaining two, subjects performed a mental arithmetic task and an isometric handgrip task during each trial (counterbalanced). Systolic blood pressure, diastolic blood pressure, heart rate, and skin conductance were recorded during the trials. The physiological responses to the two tasks were shown to vary as a function of the specific postural trial. Systolic and diastolic blood pressure were generally more sensitive to these effects than heart rate or skin conductance. The two tasks facilitated increases in blood pressure during the sitting to standing trials, especially during the standing phase. The increases in blood pressure were comparable to those reported previously for voluntary control and biofeedback procedures. Mental and physical strategies are effective in increasing blood pressure during postural change and may be useful in the management of orthostatic hypotension.

Are cardiovascular responses to behavioral stressors a stable individual difference variable in childhood?

ABSTRACTThe present paper reports two studies which address the extent to which cardiovascular responses to behavioral stress can be conceptualised as a stable individual difference variable in children. In the first study, eighth grade girls (mean age = 14.2 yrs) who had participated in a study of the familial aggregation of cardiovascular responses to behavioral stress were asked to repeat the assessment protocol when they were in (he ninth grade (mean age = 15.1 yrs). Results showed that mean task‐induced increases in diastolic blood pressure and heart rate during serial subtraction, mirror image tracing, and isometric handgrip tasks were reliable across test sessions, particularly due to the reliable increases exhibited during the mirror image tracing task. In the second study, fifth grade boys (mean age = 10.4 yrs) who had participated in a previous experiment (Matthews &amp; Jennings, 1984) of cardiovascular responses during a video game were tested in the ninth grade (mean age ‐ 14.0 yrs) in the protocol used in Study 1. Results showed that mean tusk‐induced increases in diastolic blood pressure and heart rate during video games were related to mean task‐induced increases during serial subtraction, mirror image tracing, and isometric handgrip tasks over three years Liter. The association for heart rate increases during the video game and isometric handgrip task was particularly impressive. These results suggest that task‐induced diastolic blood pressure and heart rate responses of children are stable over substantial periods of time and amiss important developmental transitions, and generalize across tasks requiring qualitatively different behavioral responses. Nonetheless, future research is needed in adults and children to further identify factors which influence the stability and generalizability of cardiovascular responses to behavioral stress.