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Vicki Ebbeck

This study examined the sources of information used by adult exercisers to judge performance. Of particular interest was the investigation of gender differences. Subjects, 271 adults (174 males, 97 females) who were enrolled in a university weight training program, completed a questionnaire designed to evaluate the importance of 12 information sources in judging weight training performance: instructor feedback, student feedback, student comparison, changes noticed outside the gym, personal attraction toward the activity, degree of perceived effort exerted in the workout, performance in workout, feedback from others not in the class, goal setting, muscle development, workout improvement over time, and ease in learning new skills. Results revealed a significant discriminant function analysis for gender, with six information sources entering the stepwise procedure: goal setting, student feedback, learning, effort, improvement, and changes noticed outside the gym differentiated the gender groups. Males relied more than females on student feedback as an information source to judge performance. Alternatively, females used effort, goal setting, improvement, and learning as information sources more than males.

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Kelly R. Rice, Catherine Gammon, Karin Pfieffer and Stewart Trost

Purpose:

The OMNI perceived exertion scale was developed for children to report perceived effort while performing physical activity; however no studies have formally examined age-related differences in validity. This study evaluated the validity of the OMNI-RPE in 4 age groups performing a range of lifestyle activities.

Methods:

206 participants were stratified into four age groups: 6-8 years (n = 42), 9-10 years (n = 46), 11-12 years (n = 47), and 13-15 years (n = 71). Heart rate and VO2 were measured during 11 activity trials ranging in intensity from sedentary to vigorous. After each trial, participants reported effort from the OMNI walk/run scale. Concurrent validity was assessed by calculating within-subject correlations between OMNI ratings and the two physiological indices.

Results:

The average correlation between OMNI ratings and VO2 was 0.67, 0.77, 0.85, and 0.87 for the 6-8, 9-10, 11-12 and 13-15 y age groups, respectively.

Conclusion:

The OMNI RPE scale demonstrated fair to good evidence of validity across a range of lifestyle activities among 6- to 15-year-old children. The validity of the scale appears to be developmentally related with RPE reports closely reflecting physiological responses among children older than 8 years.

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Chris Easton, Stephen Turner and Yannis P. Pitsiladis

The authors examined the effects of combined creatine (Cr) and glycerol (Gly) supplementation on responses to exercise in the heat. Subjects (N = 24) were matched for body mass and assigned to either a Cr or placebo (Pl) group. Twice daily during two 7-d supplementation regimens, the Cr group received 11.4 g of Cr·H2O and the Pl group received 11.4 g of glucose. Subjects in both groups also ingested 1 g of Gly/kg body mass (twice daily) in either the first or the second supplementation regimen. This design allowed 4 possible combinations of supplements to be examined (Pl/Pl, Pl/Gly, Cr/Pl, and Cr/Gly). Exercise trials were conducted pre- and post supplementation at 30 °C and 70% relative humidity. In the Pl group, total body water (TBW) increased by 0.50 ± 0.28 L after Gly and in the Cr group by 0.63 ± 0.33 L after Pl and by 0.87 ± 0.21 L after Gly. Both Cr/Pl and Cr/Gly resulted in significantly attenuated heart rate, rectal temperature, and perceived effort during exercise, although no regimen had any effect on performance. The addition of Gly to Cr significantly increased TBW more than Cr alone (P = 0.02) but did not further enhance the attenuation in HR, Tre, and RPE during exercise. These data suggest that combined Cr and Gly is an effective method of hyper hydration capable of reducing thermal and cardiovascular responses.

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John G. Williams, Roger G. Eston and Clare Stretch

This study examined the ability of 40 children (20 boys and 20 girls), ages 11 to 14 years, to regulate the intensity of their effort using perceived effort ratings during cycling. The Borg Rating of Perceived Exertion 6 to 20 Scale was learned and used as a perceptual frame of reference. Maximal oxygen uptake and power output were predicted from telemetered heart rate data collected during a submaximal graded exercise test. Subjects were then fully familiarized with the RPE scale and attended three consecutive sessions of cycling during which they adjusted the workloads themselves so as to produce effort intensities for scale ratings of 9 (very light), 13 (somewhat hard), and 17 (very hard). Heart rates were sampled during the final half minute of each session and the data were submitted to a mixed factorial analysis of variance. This showed highly significant differences (p<.001) between the three RPE levels but no significant effects for age, gender, or trials. It was concluded that the RPE is readily learned by older children and adolescents and is a potentially useful frame of reference when self-regulating effort intensity during vigorous exercise.

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Diego B. Souza, Michael Duncan and Marcos D. Polito

Purpose: To examine the effects of acute caffeine (CAF) intake on physical performance in 3 sets of unilateral knee extensions with blood-flow restriction. Methods: In a double-blind crossover design, 22 trained men ingested 6 mg·kg−1 of CAF or a placebo (PLA), 1 h prior to performing unilateral knee-extension exercise with blood-flow restriction until exhaustion (30% of 1 maximal repetition). Results: There was a significant difference in the number of repetitions between the CAF and PLA conditions in the first set (28.3 [5.3] vs 23.7 [3.2]; P = .005), second set (11.6 [3.1] vs 8.9 [2.9]; P = .03), and total repetitions performed across the 3 sets (44.5 [9.4] vs 35.0 [6.6]; P = .001). Blood lactate was also significantly different (P = .03) after exercise between the CAF (7.8 [1.1] mmol·L−1) and PLA (6.0 [0.9] mmol·L−1). In regard to pain perception, there was a difference between the CAF and PLA in the second (6.9 [1.5] vs 8.4 [1.4]; P = .04) and third sets (8.7 [0.4] vs 9.5 [0.6]; P = .01). No differences were found for perceived effort. Conclusion: Acute caffeine intake increases performance and blood lactate concentration and reduces perception of pain in unilateral knee-extension exercise with blood-flow restriction.

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Boris l. Prilutsky

The purpose of this paper is three-fold: (a) to summarize available data on coordination of major two- and one-joint muscles in multijoint tasks and identify basic features of muscle coordination, (b) to demonstrate that there may exist an optimization criterion that predicts essential features of electromyographic activity of individual muscles in a variety of tasks, and (c) to address the functional consequences of the observed muscle coordination and underlying mechanisms of its control. The analysis of the literature revealed that basic features of muscle coordination are similar among different voluntary motor tasks and reflex responses. It is demonstrated that these basic features of coordination of one- and two-joint muscles in two-dimensional tasks are qualitatively predicted by minimizing the sum of muscle stresses cubed. Functional consequences of the observed coordination of one- and two-joint muscles are (a) reduction of muscle force as well as stress, mechanical and metabolic energy expenditure, muscle fatigue, and perceived effort; (b) a spring-like behavior of a multi-joint limb during maintenance of an equilibrium posture; and (c) energy transfer between joints via two-joint muscles. A conceptual scheme of connections between motoneuron pools of one- and two-joint muscles, which accounts for the observed muscle coordination, is proposed. An important part of this scheme is the force-dependent inhibition and excitation from two-joint to one-joint synergists and antagonists, respectively.

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Daniel Viggiani and Jack P. Callaghan

A prolonged standing exposure can identify asymptomatic adults who have a higher risk of developing clinical low back pain later in life. Hip abductor cocontraction differences can predict low back pain development during standing exposures. This study’s purpose was to determine if hip abductor strength, fatigability, and recovery during prolonged standing were related to standing-induced low back pain. Forty young, asymptomatic adults (50% female) performed two 2-hour standing sessions; a fatiguing hip abductor exercise was performed prior to 1 of the 2 standing sessions. Hip abductor strength and surface electromyography of gluteus medius and tensor fascia latae were measured. Self-reported low back pain differentiated low back pain developing (PD) and nonpain developing (NPD) groups. The PD group hip abductors fatigued before the NPD group, with similar perceived effort and force losses. Mean power frequency decreases with fatigue were similar between pain groups for all muscles measured after the fatiguing exercise. Unlike NPDs, PDs did not recover force losses after 120 minutes of standing. Hip abductor fatigability may be related to the development of low back pain in this population.

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Vasilis Nikolopoulos, Melissa J. Arkinstall and John A. Hawley

The purpose of this study was to determine the effect of carbohydrate ingestion before and during intense constant load cycling to volitional fatigue on surface electromyographic (sEMG) activity from the vastus lateralis (VL) and vastus medialis (VM) muscles. After 24-h diet and training control, 8 well-trained subjects [maximal O2 uptake (VO2max) 66 ± 2 ml · kg–1· min–1; mean ± SD] ingested 8 ml · kg–1 of either a 6.4% carbohydrate-electrolyte (CHO) or a placebo (PLA) solution immediately before, followed by 2 ml · kg–1 of the same solution every 15 min while cycling to exhaustion at 84 ± 1% of VO2max. Exercise time to fatigue was 13% longer with CHO ingestion compared to PLA (58:54 ± 8:48 vs. 51:18 ± 5:54 min:s, NS). VO2 (4.22 ± 0.11 vs. 4.20 ± 0.14 L · min–1), heart rate (172 ± 4 vs. 176 ± 4 beats · min–1), ratings of perceived effort (18 ± 0.1 vs. 19 ± 0.1), and rates of carbohydrate oxidation (314 ± 28 vs. 324 ± 26 μmol · kg–1 · min–1) were similar for both PLA and CHO at exhaustion. There was no main treatment effect of CHO ingestion on blood glucose or lactate concentrations, nor plasma prolactin levels either during exercise or at fatigue. However, CHO ingestion attenuated the rise in EMG root mean square (RMS) activity during the latter stages (>45 min) of exercise and at the point of exhaustion for both VM (0.325 ± 0.010 vs. 0.403 ± 0.020 mV; p = .006) and VL (0.298 ± 0.011 vs. 0.370 ± 0.007 mV; p = .0004). We conclude that in well-trained subjects, the ingestion of carbohydrate attenuated the increase in surface electromyographic activity during intense, constant load cycling leading to exhaustion in ~1 h. The precise mechanism(s) underlying this effect cannot be attributed to alterations in CHO availability but, instead, may be linked to changes in afferent sensory input.

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Marcos A. Soriano, Amador García-Ramos, Antonio Torres-González, Joaquín Castillo-Palencia, Pedro J. Marín, Pilar Sainz de Baranda and Paul Comfort

activation, exercise-specific drills, and one set of 5 submaximal (50%–60% of the maximal perceived effort) repetitions in each exercise (PP, PJ, and SJ). Five minutes of rest was taken, followed by another set of 3 submaximal (70%–85% of the maximal perceived effort) repetitions for each exercise. After the

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Kevin S. Spink and Kayla Fesser

perceived effort at the end of the season than those who received non-normative control messages. To our knowledge, research in the activity area has been dominated by studies exploring the influence of social norms on the individuals’ own behavior (e.g.,  Crozier & Spink, 2017 ; Spink et al., 2013