Test-retest reliability of the aerobic power index component of the tri-level fitness profile in a sedentary population

Exercise-Induced Hypoalgesia in Patients with Chronic Whiplash-Associated Disorders: Differences between Subgroups Based on the Central Sensitization Inventory

BACKGROUND

Physical exercise is an important element in the rehabilitation of chronic whiplash-associated disorders, with the physiological process underlying pain reduction called exercise-induced hypoalgesia. In chronic whiplash-associated disorders, exercise-induced hypoalgesia appears impaired, and the research suggests a relationship with symptoms of dysfunctional nociceptive processing, such as central sensitization. This study improves our understanding of exercise-induced hypoalgesia in chronic whiplash-associated disorders by examining the differences between the extent of exercise-induced hypoalgesia in subgroups based on scores on the central sensitization inventory (CSI).

METHODS

Data were collected from 135 participants with chronic whiplash-associated disorders who completed a set of questionnaires. Pain pressure thresholds and temporal summations were assessed before and after a submaximal aerobic bicycle exercise test.

RESULTS

We observed no interaction effect between exercise-induced hypoalgesia and the CSI scores for both pain pressure threshold and temporal summation. No overall statistical effect was measured in the analysis of the effect of time. The pain pressure threshold significantly related to the CSI. The temporal summation showed no correlation.

CONCLUSIONS

During this study, we did not find evidence for a difference in the presence of exercise-induced hypoalgesia when the subgroups were created based on the central sensitization cluster calculator. Limited evidence was found for the influence of CSI scores on the delta pain pressure threshold.

Effect of exercise on chronic neck pain and central sensitization: A protocol for a randomized crossover trial

Exercise-induced hypoalgesia (EIH) has been found to vary widely within individuals with chronic neck pain (NP). Research has suggested that the presence of central sensitization within a subgroup of individuals with chronic NP might be a mediating factor to explain the relationship between exercise and improvements in patient-reported outcomes. Furthermore, recent work has found that lactate might play a role in the development and maintenance of chronic pain. The immediate effect of a single bout of physical exercise on central sensitization in individuals with chronic NP and the relationship between lactate concentration, central sensitization and pain sensitivity are to be investigated. Eighty adult participants with chronic NP will be recruited for this randomized crossover trial. Outcome measures, including temporal summation, conditioned pain modulation, EIH and lactate concentration, will be assessed before and after low- and high-intensity bicycling exercise. The outcomes of this study will provide new insights into the mechanistic effect of exercise on central sensitization in individuals with chronic NP and have the potential to add important information to the current exercise prescription guidelines for individuals with chronic NP. This study has been approved by the Human Research Ethics Committee, The University of Adelaide (H-2022-082) and registered in the Australian New Zealand Clinical Trials Registry (ACTRN12622000642785p).

Exploring pain mechanisms in hypermobile Ehlers-Danlos syndrome: a case-control study

BACKGROUND

The hypermobile type of Ehlers-Danlos syndrome (hEDS) is a heritable connective tissue disorder, associated with joint hypermobility and prominent chronic pain. Because experimental pain testing in hEDS is scarce, the underlying mechanisms are still poorly understood.

OBJECTIVE

The present study assesses endogenous pain facilitation and pain inhibition in hEDS, using a protocol for temporal summation of pain (TSP), conditioned pain modulation (CPM), and exercise-induced hypoalgesia (EIH).

METHODS

Twenty women with hEDS and 20 age-matched healthy controls participated. After evaluating thermal and mechanical pain thresholds (PPT), TSP was assessed using 10 repetitive painful pressure stimuli. CPM was provoked using pressure as the test stimulus and hand immersion in hot water (46°) as the conditioning stimulus. EIH was assessed after a submaximal cycling protocol.

RESULTS

The hEDS group demonstrated reduced PPTs and showed significantly more TSP after repeated painful stimuli than the control group. The increase in PPTs caused by the submaximal cycling protocol (EIH) did not reach statistical significance in the hEDS group. Furthermore, in comparison to the healthy control group, the hEDS group demonstrated significantly less EIH at the quadriceps test location. At the trapezius, EIH did not significantly differ between groups. No significant differences were found between the hEDS group and control group in the CPM response.

CONCLUSION

The results demonstrate increased TSP in hEDS, suggesting increased central pain facilitation. EIH should be studied more extensively, but may be disturbed when evaluated in working muscles. The CPM results are inconclusive and require more research.

Long-Term and Transfer Effects of an Action Control Intervention in Overweight Couples: A Randomized Controlled Trial Using Text Messages

Keeping a physically active lifestyle requires consistent self-regulatory effort such as action control (e.g., continuously monitoring and evaluating a behavior in terms of one's goals). Involving the romantic partner in interventions might be particularly effective in the long run. The present study examined the long-term and transfer effects of an action control intervention in couples using text messaging for promoting target persons' and partners' physical activity, anthropometric measures and physical fitness 6 months post baseline. A total of 121 overweight and obese romantic couples, randomly allocated to an intervention (n = 60; information + action control text messages) or a control group (n = 61; information only) and to participating as target person or partner, completed baseline assessments (T1). 100 couples (82.6%) completed the 6-month follow-up (T3) assessment. Primary outcomes included self-reported moderate-to-vigorous physical activity (MVPA) and objective MVPA and MVPA adherence using triaxial accelerometers across a diary period of 14 days after T3. Secondary outcomes included BMI, waist-to-hip circumference and physical fitness (target persons only) using a submaximal aerobic cycle test. At T3, there were no significant between-group differences between target persons and partners with regard to their objective MVPA, self-reported MVPA, BMI, waist-hip ratio or physical fitness. No significant changes in outcomes were observed from T1 to T3; however, changes in BMI from T1 to T3 between target persons and partners in the intervention group were associated. Overall, the brief 14-days action control intervention was not effective in improving target person's physical activity, body measures and physical fitness in the long-term. Moreover, no long-term benefits for partners emerged. While brief ecological momentary interventions might be a promising tool for short-term effects, future studies are needed to test features enhancing long-term effectiveness. Associations in romantic partners' changes suggest that dyadic interventions can be a promising approach, as changes induced in one partner may then transfer over to the other (controlled-trials.com ISRCTN15705531).

Reduced Parasympathetic Reactivation during Recovery from Exercise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Although autonomic nervous system (ANS) dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) has been proposed, conflicting evidence makes it difficult to draw firm conclusions regarding ANS activity at rest in ME/CFS patients. Although severe exercise intolerance is one of the core features of ME/CFS, little attempts have been made to study ANS responses to physical exercise. Therefore, impairments in ANS activation at rest and following exercise were examined using a case-control study in 20 ME/CFS patients and 20 healthy people. Different autonomous variables, including cardiac, respiratory, and electrodermal responses were assessed at rest and following an acute exercise bout. At rest, parameters in the time-domain represented normal autonomic function in ME/CFS, while frequency-domain parameters indicated the possible presence of diminished (para)sympathetic activation. Reduced parasympathetic reactivation during recovery from exercise was observed in ME/CFS. This is the first study showing reduced parasympathetic reactivation during recovery from physical exercise in ME/CFS. Delayed HR recovery and/or a reduced HRV as seen in ME/CFS have been associated with poor disease prognosis, high risk for adverse cardiac events, and morbidity in other pathologies, implying that future studies should examine whether this is also the case in ME/CFS and how to safely improve HR recovery in this population.

Neurocognitive processes mediate the relation between children's motor skills, cardiorespiratory fitness and response inhibition: Evidence from source imaging

Accumulating evidence suggests an association between outcomes of sports participation, such as motor skills and cardiorespiratory fitness, and aspects of inhibitory control in children. However, it remains unclear if motor skills and cardiorespiratory fitness are related to different source activity patterns and if neurophysiological indices of response inhibition mediate the relation of these constructs with behavioral performance. We examined the relative contributions of motor skills and cardiorespiratory fitness to response inhibition and a potential mediation by the neurocognitive processes indexed by the N200 and P300 components of event-related potentials. About 92 children aged 9-13 years completed the Movement ABC-2, the PWC170 and a Go/NoGo task. We employed electroencephalography (EEG) to record the N200 and P300 components elicited by the task, which are considered to reflect conflict monitoring and the allocation of attentional resources toward task-relevant stimuli, respectively. Path-anlayses revealed a moderate association between motor skills and behavioral performance on the Go/NoGo task. This association was fully mediated by the P300 amplitude in the NoGo condition. In contrast, cardiorespiratory fitness was not related to behavioral performance, but accounted for variance in N200. Source analyses supported an association between cardiorespiratory fitness and N200 source activity in prefrontal and primary motor cortex, whereas motor skills were related to P300 source activity in the posterior cingulate cortex. Our findings provide novel insights into the neural mechanisms underlying the relation between motor skills and response inhibition. Moreover, we found that the neural generators of the P300 and N200 varied as a function of children's cardiorespiratory fitness and motor skills.

A Combined EEG-fNIRS Study Investigating Mechanisms Underlying the Association between Aerobic Fitness and Inhibitory Control in Young Adults

The current evidence suggests that aerobic fitness is associated with inhibitory control of executive functioning in children and older adults. However, the relative contributions of different neurophysiological mechanisms to this relation remain unclear and have not yet been examined in young adults. The present study aimed to compare inhibitory control between high and low-fit young adult men, and to investigate a possible mediation of fitness effects by conflict monitoring (N450 component of event-related potentials) and lateralized oxygenation difference (LOD) in the DLPFC. For the present cross-sectional study, participants with different physical activity levels were recruited and divided into low-fit and high-fit participants based on relative power on the PWC170. A Stroop Color-Word task was administered and combined EEG-fNIRS was simultaneously utilized to assess the N450 and LOD, because these parameters are linked with behavioral performance. The results of the statistical analysis showed that high-fitcompared to low-fit participants showed less Stroop interference and lower negativity of the N450, whereas no difference was found for LOD. Path-analyses further revealed that the relation between aerobic fitness levels and Stroop interference was indirect and mediated by N450. In contrast, LOD was inversely correlated with Stroop interference, but did not explain the relation of aerobic fitness with behavioral performance. The present findings indicate that greater inhibitory control in high- compared to low-fit young men can be explained by more effective conflict monitoring. Moreover, young adults with left-lateralizedDLPFC oxygenation also show higher inhibitory control, but this oxygenation pattern is not influenced by aerobic fitness.

Exercise-induce hyperalgesia, complement system and elastase activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome - a secondary analysis of experimental comparative studies

Background and aims The interaction between the immune system and pain has been thoroughly explored in the recent decades. The release of inflammatory mediators from immune cells has the capability of activating neurons and glial cells, in turn sensitizing the nervous system. Both immune system alterations and pain modulation dysfunctions have been shown in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) following exercise. However, no studies tried to explore whether these two phenomena are linked and can explain exercise-induced symptoms worsening in people with ME/CFS. We hypothesized that exercise-induced changes in descending pain modulation is associated to changes in immune system functions. We used complement system product C4a and elastase activity as indicators of immune system activity. Methods The study design was a secondary analysis of controlled experimental studies. Twenty-two patients with ME/CFS and 22 healthy sedentary controls were enrolled. In experiment 1, subjects performed an aerobic submaximal exercise test; in experiment 2 they underwent a self-paced exercise test. One week of rest period were set between the two exercise tests. Before and after each experiment, subjects underwent clinical assessment, pain thresholds (PPTs) measurement, and blood sampling. Immune system function was assessed measuring complement system C4a products and elastase activity. Results Changes in elastase activity were not associated to changes in PPTs. Associations were observed in the ME/CFS group between changes in PPTs and C4a products, following both types of exercise. After submaximal exercise, the change in C4a products was associated with the change in PPT at the thumb in patients (r=0.669, p=0.001). Similarly, after self-paced exercise the change in C4a products was associated witht the change in PPT at the calf in patients (r=0.429, p=0.047). No such correlations were found in healthy controls. Regression analysis showed that C4a changes after the submaximal exercise significantly predicted the change in PPTs (R2=0.236; p=0.02). Conclusions Moderate associations between exercise-induced changes in PPTs and immune system activity were found only in ME/CFS. The change in the complement system following submaximal exercise might be able to explain part of the change in patient's pain thresholds, providing evidence for a potential link between immune system alteration and dysfunctional endogenous pain modulation. These results have to be taken with caution, as only one out of three measures of PPTs was found associated with C4a changes. We cannot reject the hypothesis that C4a might therefore be a confounding factor, and changes during exercise might be mediated by other mechanism. Implications Immune system changes following exercise might contribute to exercise-induced symptoms worsening in patients with ME/CFS. However, the role of the complement system is questionable.

The effect of backpack load placement on physiological and self-reported measures of exertion

BACKGROUND

Backpacks are the most popular way of carrying additional weight; however, it puts the body under physical stress and may cause discomfort. It may also increase oxygen demand and energy cost. Manipulation of load placement may relieve the effects carrying a backpack has on the body.

OBJECTIVE

This study investigated physiological and self-reported measures of exertion, movement economy and efficiency, carrying a loaded backpack in high and low load placement compared to a control condition.

METHOD

Fifteen healthy adults were examined under three load conditions: no load, carrying a 20% of body weight in high and low load placement. Dependent variables were measured using a metabolic measurement system and participants rated their perceived exertion on a Borg scale.

RESULT

Carrying load produced a significant increase in VO2, minute ventilation, heart rate, movement economy and overall perceived exertion in both load placements compared with the no backpack condition. However, no difference was observed between the high and low load placement conditions.

CONCLUSION

While altering load placement did not influence physiological variables or overall exertion, participants reported lower perceived exertion on the shoulders in low load placement and low load placement might be preferable in this respect.

Exercise and Cognitive Functioning in People With Chronic Whiplash-Associated Disorders: A Controlled Laboratory Study

STUDY DESIGN

Controlled laboratory study.

BACKGROUND

In addition to persistent pain, people with chronic whiplash-associated disorders (WAD) commonly deal with cognitive dysfunctions. In healthy individuals, aerobic exercise has a positive effect on cognitive performance, and preliminary evidence in other chronic pain conditions reveals promising results as well. However, there is evidence that people with chronic WAD may show a worsening of the symptom complex following physical exertion.

OBJECTIVE

To examine postexercise cognitive performance in people with chronic WAD.

METHODS

People with chronic WAD (n = 27) and healthy, inactive, sex- and age-matched controls (n = 27) performed a single bout of an incremental submaximal cycling exercise. Before and after the exercise, participants completed 2 performance-based cognitive tests assessing selective and sustained attention, cognitive inhibition, and simple and choice reaction time.

RESULTS

At baseline, people with chronic WAD displayed significantly lower scores on sustained attention and simple reaction time (P<.001), but not on selective attention, cognitive inhibition, and choice reaction time (P>.05), compared with healthy controls. Postexercise, both groups showed significantly improved selective attention and choice reaction time (chronic WAD, P = .001; control, P<.001), while simple reaction time significantly increased (P = .037) only in the control group. In both groups, no other significant changes in sustained attention, cognitive inhibition, pain, and fatigue were observed (P>.05).

CONCLUSION

In the short term, postexercise cognitive functioning, pain, and fatigue were not aggravated in people with chronic WAD. However, randomized controlled trials are required to study the longer-term and isolated effects of exercise on cognitive functioning.

Effect of a physical conditioning versus health promotion intervention in dancers: a randomized controlled trial

Although dancing requires extensive physical exertion, dancers do not often train their physical fitness outside dance classes. Reduced aerobic capacity, lower muscle strength and altered motor control have been suggested as contributing factors for musculoskeletal injuries in dancers. This randomized controlled trial examined whether an intervention program improves aerobic capacity and explosive strength and reduces musculoskeletal injuries in dancers. Forty-four dancers were randomly allocated to a 4-month conditioning (i.e. endurance, strength and motor control training) or health promotion program (educational sessions). Outcome assessment was conducted by blinded assessors. When accounting for differences at baseline, no significant differences were observed between the groups following the intervention, except for the subscale "Pain" of the Short Form 36 Questionnaire (p = 0.03). Injury incidence rate and the proportion of injured dancers were identical in both groups, but dancers following the conditioning program had significant less low back injuries (p = 0.02). Supplementing regular dance training with a 4-month conditioning program does not lead to a significant increase in aerobic capacity or explosive strength in pre-professional dancers compared to a health promotion program without conditioning training, but leads to less reported pain. Further research should explore how additional training may be organized, taking into account the demanding dance schedule of pre-professional dancers. The trial is registered at ClinicalTrials.gov, number NCT01440153.

Oxygen Consumption at 30 W of Exercise Is Surrogate for Peak Oxygen Consumption in Evaluation of Cardiorespiratory Fitness in Young-Adult African-American Females

Body mass index (BMI) is negatively correlated with cardiorespiratory fitness, measured by maximal or peak oxygen consumption (VO_2peak). VO_2peak measurements require heavy aerobic exercise to near exhaustion which increases the potential for adverse cardiovascular events. This study tests the hypothesis that VO₂ measured at a fixed submaximal workload of 30 W is a surrogate for VO_2peak. We studied 42 normotensive African-American female university students, 18–25 years of age. We measured VO_2peak, blood pressure, and VO₂ at a 30 W exercise workload and computed BMI. We found significant negative correlations between BMI and VO_2peak (r = −0.41, P < 0.01) and between BMI and VO₂ at 30 W (r = −0.53, P < 0.001). Compared to VO_2peak, VO₂ at 30 W increased the significance of the negative correlation with BMI. The heart rate-systolic pressure product at 30 W was positively correlated with BMI (r = 0.36, P < 0.01) and negatively correlated with VO_2peak (r = −0.38, P < 0.001). The positive correlation between BMI and the heart rate-systolic pressure product and the greater negative correlation between VO₂ and BMI at 30 W of exercise than that at exercise to fatigue suggest that normalized measurements of VO₂ at the fixed exercise workload of 30 W could be useful surrogates for measurements of VO_2peak.

Effects of aerobic endurance, muscle strength, and motor control exercise on physical fitness and musculoskeletal injury rate in preprofessional dancers: an uncontrolled trial

OBJECTIVE

The purpose of this study was to evaluate musculoskeletal injury rate and physical fitness before and 6 months after an endurance, strength, and motor control exercise program in preprofessional dancers.

METHODS

This uncontrolled trial was completed at a college offering a professional bachelor degree in dance. Forty preprofessional dancers underwent a test battery before and after a 6-month lasting exercise program in addition to their regular dance lessons. Physical fitness was evaluated by means of a submaximal exercise test with continuous physiological monitoring and by a field test for explosive strength. Anthropometric measurements were taken to analyze the influence of fitness training on body composition. Musculoskeletal injury incidence and quality of life were recorded during the 6-month lasting intervention. An intention-to-treat analysis ("last observation carried forward" method) was used with a Student t test for normally distributed variables. The Wilcoxon signed rank and Mann-Whitney U tests were used as nonparametric tests.

RESULTS

Physical fitness improved after the 6 months of additional training program (P<.05). The waist:hip ratio (P=.036) and the sum of the measured subcutaneous skin thickness (P=.001) significantly decreased. Twelve dancers developed musculoskeletal complaints, requiring temporary interruption of dancing.

CONCLUSIONS

The combination of regular dance lessons with an additional exercise program resulted in improved physical fitness in preprofessional dancers, without affecting the aesthetical appearance. A relatively high injury rate was observed during the intervention period. These results suggest that a randomized, controlled trial should be performed to examine the effectiveness of additional exercise in dancers on physical fitness and musculoskeletal injury rate.

Pain inhibition and postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: an experimental study

OBJECTIVES

To examine the efficacy of the pain inhibitory systems in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) during two different types of exercise and to examine whether the (mal)functioning of pain inhibitory systems is associated with symptom increases following exercise.

DESIGN

A controlled experimental study.

SETTING AND SUBJECTS

Twenty-two women with ME/CFS and 22 healthy sedentary controls were studied at the Department of Human Physiology, Vrije Universiteit Brussel.

INTERVENTIONS

All subjects performed a submaximal exercise test and a self-paced, physiologically limited exercise test on a cycle ergometer. The exercise tests were undertaken with continuous cardiorespiratory monitoring. Before and after the exercise bouts, subjects filled out questionnaires to assess health status, and underwent pressure pain threshold measurements. Throughout the study, subjects' activity levels were assessed using accelerometry.

RESULTS

In patients with ME/CFS, pain thresholds decreased following both types of exercise, whereas they increased in healthy subjects. This was accompanied by a worsening of the ME/CFS symptom complex post-exercise. Decreased pressure thresholds during submaximal exercise were associated with postexertional fatigue in the ME/CFS group (r = 0.454; P = 0.034).

CONCLUSIONS

These observations indicate the presence of abnormal central pain processing during exercise in patients with ME/CFS and demonstrate that both submaximal exercise and self-paced, physiologically limited exercise trigger postexertional malaise in these patients. Further study is required to identify specific modes and intensity of exercise that can be performed in people with ME/CFS without exacerbating symptoms.

Unravelling the nature of postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: the role of elastase, complement C4a and interleukin-1beta

OBJECTIVES

Too vigorous exercise or activity increase frequently triggers postexertional malaise in people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a primary characteristic evident in up to 95% of people with ME/CFS. The present study aimed at examining whether two different types of exercise results in changes in health status, circulating elastase activity, interleukin (IL)-1beta and complement C4a levels.

DESIGN

Comparative experimental design.

SETTING

University.

SUBJECTS

Twenty-two women with ME/CFS and 22 healthy sedentary controls

INTERVENTIONS

participants were subjected to a submaximal exercise (day 8) and a self-paced, physiologically limited exercise (day 16). Each bout of exercise was preceded and followed by blood sampling, actigraphy and assessment of their health status.

RESULTS

Both submaximal exercise and self-paced, physiologically limited exercise resulted in postexertional malaise in people with ME/CFS. However, neither exercise bout altered elastase activity, IL-1beta or complement C4a split product levels in people with ME/CFS or healthy sedentary control subjects (P > 0.05). Postexercise complement C4a level was identified as a clinically important biomarker for postexertional malaise in people with ME/CFS.

CONCLUSIONS

Submaximal exercise as well as self-paced, physiologically limited exercise triggers postexertional malaise in people with ME/CFS, but neither types of exercise alter acute circulating levels of IL-1beta, complement C4a split product or elastase activity. Further studying of immune alterations in relation to postexertional malaise in people with ME/CFS using multiple measurement points postexercise is required.

Reliability of health-related physical fitness tests in European adolescents. The HELENA Study

OBJECTIVE

To examine the reliability of a set of health-related physical fitness tests used in the European Union-funded Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) Study on lifestyle and nutrition among adolescents.

DESIGN

A set of physical fitness tests was performed twice in a study sample, 2 weeks apart, by the same researchers.

PARTICIPANTS

A total of 123 adolescents (69 males and 54 females, aged 13.6+/-0.8 years) from 10 European cities participated in the study.

MEASUREMENTS

Flexibility, muscular fitness, speed/agility and aerobic capacity were tested using the back-saver sit and reach, handgrip, standing broad jump, Bosco jumps (squat jump, counter movement jump and Abalakov jump), bent arm hang, 4 x 10 m shuttle run, and 20-m shuttle run tests.

RESULTS

The ANOVA analysis showed that neither systematic bias nor sex differences were found for any of the studied tests, except for the back-saver sit and reach test, in which a borderline significant sex difference was observed (P=0.044). The Bland-Altman plots graphically showed the reliability patterns, in terms of systematic errors (bias) and random error (95% limits of agreement), of the physical fitness tests studied. The observed systematic error for all the fitness assessment tests was nearly 0.

CONCLUSIONS

Neither a learning nor a fatigue effect was found for any of the physical fitness tests when repeated. The results also suggest that reliability did not differ between male and female adolescents. Collectively, it can be stated that the reliability of the set of physical fitness tests examined in this study is acceptable. The data provided contribute to a better understanding of physical fitness assessment in young people.

Using Electromyography to Detect the Weightings of the Local Muscle Factors to the Increase of Perceived Exertion During Stepping Exercise

Rate of perceived exertion (RPE) is a clinically convenient indicator for monitoring exercise intensity in cardiopulmonary rehabilitation. It might not be sensitive enough for clinicians to determine the patients' physiological status because its association with the cardiovascular system and local muscle factors is unknown. This study used the electromyographic sensor to detect the local muscle fatigue and stabilization of patella, and analyzed the relationship between various local muscle and cardiovascular factors and the increase of RPE during stepping exercise, a common exercise program provided in cardiopulmonary rehabilitation. Ten healthy adults (4 males and 6 females) participated in this study. Each subject used their right bare foot to step up onto a 23-cm-high step at a constant speed until the RPE score reached 20. The RPE, heart rate (HR), and surface EMG of the rectus femoris (RF), vastus medialis, and vastus lateralis were recorded at 1-minute intervals during the stepping exercise. The generalized estimating equations (GEE) analysis indicated that the increase in RPE significantly correlated with the increase in HR, and decrease in median frequency (MF) of the EMG power spectrum of the RF. Experimental results suggest that the increase in RPE during stepping exercise was influenced by the cardiovascular status, localized muscle fatigue in the lower extremities. The weighting of the local muscle factors was more than half of the weighting of the cardiovascular factor.

Test–retest reliability of the Aerobic Power Index submaximal exercise test in an obese population

Many overweight and obese individuals have difficulty in performing aerobic fitness tests that require maximal exertion. Therefore, the purpose of this study was to investigate the reliability of the Aerobic Power Index (API) submaximal aerobic exercise test, as well as associated variables consisting of oxygen uptake (mlkg(-1)min(-1)) and ratings of perceived exertion (RPE) in an obese population. Twenty-two obese subjects (3 males and 19 females) aged between 36 and 68 years (mean=45.7+/-9.8 years), with BMI's ranging between 30.45 and 39.18kgm(-2) (mean=33.63+/-2.6), participated in two trials that was performed on the same weekday at the same time, but 1 week apart. Intraclass correlation coefficient (ICC) scores for power output (Wkg(-1)) and oxygen uptake O(2) (mlkg(-1)min(-1)) were highly reliable (R(1)=0.95 and 0.96, respectively), while the ICC score for RPE was moderately reliable (R(1)=0.88). Technical error of measurement results for power output (Wkg(-1)), O(2) (mlkg(-1)min(-1)), and RPE were 0.07Wkg(-1), 0.71mlkg(-1)min(-1), and 0.92, respectively. Additionally, a Pearson product-moment correlation coefficient demonstrated a strong relationship between power output (Wkg(-1)) and O(2) (mlkg(-1)min(-1)) for trial 1 (r=0.90) and for trial 2 (r=0.89). Results from this study demonstrated that the API submaximal aerobic exercise test is a highly reliable protocol for use in an obese population, and can be considered as an alternative exercise test to other submaximal cycle tests.

Reliability of physiological, psychological, and cognitive variables in chronic fatigue syndrome

The purpose of this study was to assess the reliability of specific physiological, psychological, and cognitive variables in 31 chronic fatigue syndrome (CFS) subjects and 31 matched control subjects. All variables were assessed weekly over a 4-week period and reliability was determined using an intraclass correlation coefficient (ICC). Results ranged from moderately to highly reliable for all variables assessed, except for mental and physical fatigue, which were of questionable reliability in both groups (ICC = 0.61 and 0.65, respectively, for the CFS group; 0.62 and 0.52 for the control group). A Pearson product-moment correlation analysis that compared exercise performance with all psychological variables assessed, demonstrated a significant relationship between exercise performance and depression (r = .41, P = .02) in week 3 only, suggesting minimal association between objective performance and psychological responses. These correlation results support a central, as opposed to a peripheral, basis to the sensation of fatigue in CFS.

Physiological Responses during a Submaximal Cycle Test in Chronic Fatigue Syndrome

INTRODUCTION/PURPOSE

Numerous studies have assessed physical function in individuals suffering from chronic fatigue syndrome (CFS) but neglected to match control subjects according to current activity levels, consequently casting doubt on reported results. The purpose of this study was to include current activity levels as one criterion for matching CFS subjects with healthy control subjects in order to more accurately assess physical function in these subjects.

METHODS

Thirty-one healthy control subjects were matched to CFS subjects according to age, gender, body mass, height, and current activity levels. Physiological function was assessed weekly over a 4-wk period using a submaximal cycle test.

RESULTS

Comparison of absolute physiological results recorded at the end of each incremental work level of the exercise test showed that ratings of perceived effort (RPE) was the only variable that was significantly different between the two groups. Scores for RPE were significantly higher in CFS subjects for each incremental work level assessed. Conversely, results recorded on completion of the exercise test showed that the control group was capable of a greater power output than the CFS group as reflected by significantly higher scores for watts per kilogram (P < 0.0005), net lactate production (P = 0.003), oxygen uptake (mL x kg(-1) x min(-1); P < 0.0005), respiratory exchange ratio (P = 0.021), and HR values as a percentage of age predicted HR(max) (P = 0.001). End-point RPE scores were again significantly higher in the CFS group (P < 0.0005).

CONCLUSION

It is proposed that the reduced exercise tolerance in CFS is due to impairment in the mechanisms that constitute effort sense and/or to avoidance behaviors that result in a reluctance by these subject to exercise to full capacity.