International Journal of Exercise Science

Multiple Models Can Concurrently Explain Fatigue During Human Performance

C. Matthew Laurent — Fri, 16 Oct 2009 08:28:52 PDT

One of the most commonly and thoroughly studied paradigms of human performance is fatigue. However, despite volumes of research there remains considerable controversy among scientists regarding definitive conclusions about the specific mechanism(s) contributing to fatigue. Within the literature there are three primary yet distinctly different governing ideas of fatigue; the traditionally referenced central model and peripheral model as well as the emerging central governor model (CGM). The CGM has recently been advocated by a limited number of researchers and is suggestive of a more integrative model of fatigue when compared the traditional peripheral and central models. However, more work is needed to determine the specific and perhaps synergistic roles of each paradigm during exercise or sport activity. This article contains three components; (1) a brief overview of the problems associated with defining fatigue, (2) a description of the models governing interpretation of fatigue and, (3) a presentation of multiple interpretations of selected data to demonstrate that some results can be reasonably explained using multiple models of fatigue, often concurrently. The purposes of this paper are to reveal that a) perhaps it is not the results that suggest a certain paradigm of regulation, yet that it may be a product of an a priori definition that is being employed and b) an integrative model of central and peripheral fatigue may present a plausible explanation for fatigue vs. adherence to the notion that each paradigm is mutually exclusive.

Determination of Force Corresponding to Maximal Lactate Steady State in Tethered Swimming

Marcelo Papoti — Fri, 16 Oct 2009 08:28:50 PDT

The main aim of the present investigation was to verify if the aerobic capacity (AC) measured in tethered swimming corresponds to the maximal lactate steady state (MLSS) and its correlation with 30 min and 400m free style swimming. Twenty-five swimmers were submitted to an incremental tethered swimming test (ITS) with an initial load of 20N and increments of 10N each 3min. After each stage of 3min, the athletes had 30s of interval to blood sample collections that were used to measure blood lactate concentrations ([La-]). The ACBI was determined by the abrupt increase in [La-] versus force (F). The points obtained between [La-] versus force (N) were adjusted by an exponential curve model to determine AC corresponding to 3.5mmol.l-1 (AC3.5) and 4.0mmol.l-1 (AC4.0). After these procedures, the swimmers performed maximal efforts of 30min and 400m in free style swimming. We used the distance performed in 30min and the time performed in 400m to calculate the median velocities (i.e. V30 and V400) of these protocols. After one week, in order to measure the MLSS, nine athletes performed three 30-min tethered swimming efforts with intensities of 90, 100, and 110% of ACBI. The ANOVA one-way was used to compare the ACBI, AC3.5 and AC4.0. Correlations between ACs, and between ACs and V30 and V400 (p<0.05) were determined using the Pearson's correlation coefficient. The intensity corresponding to 100% of ACBI was similar to the MLSS. It was observed significant correlations of the aerobic capacities (i.e. ACBI, AC3.5 and AC4.0) with V30 (r>0.91) and V400 (r>0.63). According to our results, it is possible to conclude that the ACBI corresponds to the MLSS, and both the AC - individually determined - and the AC - determined using fixed blood lactate concentrations of 3.5 and 4.0mmol.l-1 - can be used to predict the mean velocity of 30min and 400m in free style swimming. In addition to that, the tethered swimming system can be used for aerobic development in places where official sized swimming pools are not available, such as rehabilitation clinics and health clubs.

The Short-Term Effect of Whole Body Vibration Training on Sprint Start in Collegiate Athletes

Brad Roberts* — Fri, 16 Oct 2009 08:22:40 PDT

Whole body vibration (WBV) is characterized by a vibratory stimulus emitted throughout the body through the use of a vibrating platform on which the subject stands. Studies have shown over 30% increases in maximal explosive strength such as maximal speed biceps curl as well as increases in maximum dynamic force such as maximal sitting bench pull as the result of vibration. The purpose of this study was to investigate the effects of short term whole-body vibration on sprint starts among collegiate track athletes. On the first day eleven subjects were randomly assigned to either a non-vibration or vibration group for initial testing. The vibration group used whole body vibration along with their normal warm-up routine while the non-vibration group did not. Force measurements were taken where the starting blocks were placed using a force plate embedded under the track surface following the warm up. One week later the groups alternated. The results were then compared between vibration and non-vibration groups for individual athletes. The vibration protocol occurred for 60 s at 26 Hz with an amplitude of 4mm on a Galileo 2000 platform. Repeated measures analysis of the variance showed peak resultant force was 6% greater when the vibration platform was utilized prior to the start (p=0.013). Further research is needed to determine whether any meaningful differences exist in sprint start velocity as a result of WBV. There were no observed differences in the 30m sprint times.

Evaluation of Hand-to-Hand Bioelectrical Impedance Analysis for Estimating Percent Body Fat in Young Adults

Aaron M. Weaver* — Fri, 16 Oct 2009 08:19:32 PDT

Purposes were to (a) to examine the validity and precision of a hand-to-hand bioelectrical impedance analyzer (HBIA) and (b) to determine the effect of an acute sub-maximal aerobic exercise bout on HBIA percent body fat (%BF) measures. Forty-one young adults (21 women; 20 men) visited the laboratory for body composition assessment on two separate occasions. During the control session, %BF was assessed by HBIA twice, before and immediately after 30 min of rest, and once by air-displacement plethysmography (ADP), using the BOD POD, which was considered the criterion method for comparison. During the exercise session, HBIA %BF measurements were determined prior-to and immediately after 30 minutes of moderate-intensity treadmill exercise. HBIA significantly underestimated %BF in the total sample (mean difference (MD) = 1.4 � 4.3%) and, when examined by gender, in the women (MD = 2.4 � 4.1%). The standard errors of estimate (range 4.1-4.3%) also exceeded the recommended range for accuracy (<3.5%). Following exercise, there was minimal, but statistically significant reduction in HBIA-measured %BF pre- to post-exercise for the total sample (19.6 � 6.0 vs. 19.3 � 6.0%; p = 0.011). HBIA underestimated %BF when compared to ADP and the individual prediction error exceeded current recommendations when assessing young adults. In addition, performing sub-maximal aerobic exercise prior to the assessment decreased the %BF estimate. When one factors the exercise-induced alterations with the currently observed tendency for HBIA to underestimate %BF, it is apparent that exercise may further reduce the accuracy of this method.

A Kinematic and Kinetic Case Study of a Netball Shoulder Pass

Sharon A. Hetherington* — Fri, 16 Oct 2009 08:16:02 PDT

The majority of studies analysing netball skills using force platforms have focused on reducing the risk of injury from compression and torsion forces on the knee and ankle joints during landing and pivoting. In this preliminary case study our aim was to investigate the efficacy of a combination of tools to describe the kinematic and kinetic mechanisms underlying the netball shoulder pass. The segmental movements of the netball shoulder pass were analysed from video and force platform data in order to develop a suitable methodology for use in a larger study. Peak vertical ground reaction force of 850 N was found to coincide with the point of maximum velocity of the centre of pressure, occurring 40 ms before ball release. The participant's centre of pressure continued anteriorly for 40 ms after ball release. The wrist traveled in a linear path during the propulsion phases, maximising impulse to the ball. A large shear force also occurred in the anterior posterior direction coinciding with ball release due to friction between the left shoe and the force platform, resisting the forward momentum of the body. Negative acceleration of the upper limb following the propulsion phase reached a peak of 68.6 rad/s-2 for the arm and 82.4 rad/s-2 for the forearm. Peak shoulder deceleration torque was calculated at 4.1 Nm which was greater than during acceleration (1.6 Nm). The combination of kinematic and kinetic tools yielded a comprehensive analysis of the investigated skill. Future biomechanical studies may determine differences in skill execution between novice and professional players or variability in movement within a population of skilled netball players.

Psychosocial Correlates of Physical Activity in Children and Adolescents in a Rural Community Setting

Kelly Crimi — Fri, 16 Oct 2009 07:53:17 PDT

The purpose of this study was to evaluate the relationships between selected psychosocial factors and the physical activity behaviors of children (grade 4-8) and adolescents (grades 9-12) in a rural community setting. The Children's Physical Activity Scale (CPAC)was used to measure the psychosocial factors of physical activity, The Physical Activity Questionnaire-Children (PAQ-C), and Physical Activity Questionnaire-Adolescents (PAQ-A) were used to measure the physical activity behaviors of the 167 participants. Results indicated that male and female physical activity behaviors were not significantly different. However, physical activity declined with age [F(8,147) = 5.44, p < 0.05, ES = 0.23]. All psychosocial factors were significantly correlated with physical activity in youth with the single highest correlation for males being "liking of exercise" (r = .61) and the highest correlation for females was "liking of games and sports"(r = .44). Stepwise regression analyses identified three subscales (liking of games and sport, liking of exercise, and parental support) in a significant prediction model of physical activity in both genders. The results indicate that children's physical activity is associated with a variety of psychosocial variables that represent import predisposing and reinforcing factors.

Balance Across Boundaries: Service Learning from an International Perspective

Teresa C. Fitts — Fri, 16 Oct 2009 07:53:16 PDT

Service-Learning provides students, faculty and community partners an opportunity to go beyond classroom and laboratory instruction to the application of theoretical principles, and the development of civic responsibility by forging meaningful relationships with community partners. Service-learning also enables faculty to broaden the cultural sensitivity and international exposure of students by engaging students in directed, purposeful projects aimed at supporting the goals of both the college and the international partners. We have a unique opportunity in Exercise Science to make lasting changes and improve global conditions relating to student learning and the physical inactivity crisis.The purpose of this article is to define service-learning, describe different types of service-learning projects, and discuss service-learning opportunities in international settings.

Comparison of the Power Plate and Free Weight Exercises on Upper Body Muscle Endurance in Young Athletes

Elisabeth Boland* — Wed, 29 Jul 2009 08:15:29 PDT

The power plate (PP) is designed to reduce training time while providing a muscle stimulus that leads to positive changes in muscle mass. This study investigated the effect that training on the PP has compared to a free-weight (FW) program, on upper body endurance, defined as the number of push-ups completed at one time prior to failure. Following IRB approval a pre-test was used to assess push-up endurance in PP and FW cohorts. Each group exercised for six consecutive weeks, working out three times per week, on non-consecutive days performing five exercises of two sets of 8-12 repetitions. Twenty-two females and 2 males enrolled in the investigation. Eleven with a mean age of 22 years (20-24) participated in the PP cohort. Thirteen participated in the FW arm of the study with a mean age of 24.5 (20-29) years. Shapiro-Wilk found lack of data normality. Wilcoxon Rank Sum testing yielded statistically significant differences within groups. The FW comparison between pre and post test showed a p value of 0.016. The PP group pre to post test p value was 0.005. Nonparametric testing (Mann Whitney) found no statistical differences (p=0.62) between Group A (FW) and Group B (PP) on the push-up pre-test. The post-test comparing post testing differences between groups (PP and FW) found no statistical differences (p=0.55) in the push-up test. Subjects in both groups saw increases in upper-body endurance with statistically significant differences within groups. Based on our findings the PP is a useful tool which enhances upper body muscle endurance.

Predictors of ADL Disability in Culturally Diverse Older Adults

Fernanda Winchester — Wed, 29 Jul 2009 08:03:09 PDT

The purpose of this study was to utilize the disablement pathway model to examine the contribution of physical function, dyspnea, and pain to disability in activities-of-daily-living (ADL) in culturally diverse older adults. Participants were 51 older adults (age = 69.0 years � 9.7; 76.5% African-American, 51.0% < high school education, 52.9% < $20,000 annual income) from an urban community center and an independent living housing facility for seniors. Participants completed the Functional Status Index (FSI), which provides ratings of need for assistance (FSIA) and pain (FSIP) with ADL, the Continuous Scale Physical Functional Performance 10-item Test (CS-PFP10), and an analog dyspnea scale. Hierarchical multiple regression analyses revealed that facility, physical function, pain, and dyspnea accounted for 50.5% of the variance in disability and that pain (β = .43, p < .01) and physical function (β = -.39, p < .01) were the only significant predictors. In the second model, facility, dyspnea, and pain explained 27.6% of the variance in physical function, and facility (β = .39, p < .01) and dyspnea (β = -.26, p = .05) were the only significant predictors. Based on the disablement pathway model, physical functional improvement and pain prevention and management should be targeted when designing culturally appropriate strategies for delaying disability and maintaining independent life.

Consequences of Weight Cycling: An Increase in Disease Risk?

Kelley Strohacker — Mon, 27 Jul 2009 20:30:30 PDT

Research indicates that weight cycling, or "yo-yo dieting" is a common occurrence in obese populations. The long term negative health consequences of weight cycling are debated and it is unclear whether or not this weight change pattern poses a greater disease risk compared to obesity maintenance. This review discusses the prevalence of weight cycling and physiological alterations occurring during weight loss that promotes weight regain. We also discuss the effect weight regain has upon adipose tissue in terms of rate and type of accumulation. Also within this review are discussions surrounding the previously published literature based upon human and rodent research. We focus on previous limitations and difference in experimental design that have perhaps resulted in mixed findings concerning independent effects of weight cycling on health parameters. The final purpose of this review is to discuss future directions in evaluating the pro-inflammatory response to weight cycling in order to compare the disease risk compared to obesity maintenance.