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Diane K. Ehlers and Jennifer L. Huberty

Background:

The purpose of this study was to describe which theory-based behavioral and technological features middle-aged women prefer to be included in a mobile application designed to help them adopt and maintain regular physical activity (PA).

Methods:

Women aged 30 to 64 years (N = 120) completed an online survey measuring their demographics and mobile PA application preferences. The survey was developed upon behavioral principles of Social Cognitive Theory, recent mobile app research, and technology adoption principles of the Unified Theory of Acceptance and Use of Technology. Frequencies were calculated and content analyses conducted to identify which features women most preferred.

Results:

Behavioral features that help women self-regulate their PA (PA tracking, goal-setting, progress monitoring) were most preferred. Technological features that enhance perceived effort expectancy and playfulness were most preferred. Many women reported the desire to interact and compete with others through the application.

Conclusions:

Theory-based PA self-regulation features and theory-based design features that improve perceived effort expectancy and playfulness may be most beneficial in a mobile PA application for middleaged women. Opportunities to interact with other people and the employment of social, game-like activities may also be attractive. Interdisciplinary engagement of experts in PA behavior change, technology adoption, and software development is needed.

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Kevin L. Lamb

This study examined the validity and reliability of the Rating of Perceived Exertion (RPE) scale and the Children’s Effort Rating Table (CERT) as methods of regulating exercise intensity during discontinuous cycle ergometry. Sixty-four school children (ages 9–10) were randomly assigned to one of two groups, RPE or CERT, and received two trials 7 days apart. On both occasions, subjects produced 4 × 4-min scale-specific exercise intensities—3, 5, 7, and 9 (CERT) or 8, 12, 15, and 18 (RPE)—interspersed with 2-min rest periods. Analyses yielded significant (p < .01) correlations between perceived effort levels and objective measures: r = .47 to .61 (heart rate) and r = .59 to .75 (power output). Intraclass correlations indicated satisfactory overall repeatability of the produced exercise intensities (R > .70), but some notable inconsistencies were observed. The usefulness of effort perception scales among preadolescent children is presently rather limited, probably due to a number of confounding factors that need to be systematically addressed.

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Herbert W. Marsh

Physical activity measures for a large, nationally representative sample of Australian boys and girls aged 9, 12, and 15 were related to multiple dimensions of physical fitness. Physical activity during a one-week period was only modestly related to physical fitness. However, relations tended to be higher for length of time multiplied by METs (METs - minday1) than for time alone, time multiplied by perceived effort, or METs - min day−1 multiplied by effort, whereas time multiplied by effort did no better than time alone. Relations tended to be nonlinear in that progressively higher levels of activity had less positive associations with physical fitness. The pattern and size of the relations were consistent across scores for boys and girls aged 9 to 15. Self-report measures of typical and recent (within one week) physical activity both contributed to the prediction of physical fitness, indicating that both aspects of physical activity are important.

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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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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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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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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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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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Boris I. Prilutsky

In this response, the major criticisms of the target article are addressed. Terminology from the target article that may have caused some confusion is clarified. In particular, the tasks that have the basic features of muscle coordination, as identified in the target article, have been limited in scope. Anew metabolic optimization criterion suggested by Alexander (2000) is examined for its ability to predict muscle coordination in walking. Issues concerning the validation of muscle force predictions, the rules of muscle coordination, and the role of directional constraints in coordination of two-joint muscles are discussed. It is shown in particular that even in one-joint systems, the forces predicted by the criterion of Crowninshield and Brand (1981) depend upon the muscle moment arms and the physiological cross-sectional areas in much more complex ways than either previously assumed in the target article, or incorrectly derived by Herzog and Ait-Haddou (2000). It is concluded that the criterion of Crowninshield and Brand qualitatively predicts the basic coordination features of the major one- and two-joint muscles in a number of highly skilled, repetitive motor tasks performed by humans under predictable conditions and little demands on stability and accuracy. A possible functional significance of such muscle coordination may be the minimization of perceived effort, muscle fatigue, and/or energy expenditure.

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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.