Effect of creatine supplementation on cycle ergometer exercise in a hyperthermic environment

In order to examine thermoregulatory response to creatine (CR) supplementation, competitive male cyclists and triathletes (n = 7, VO2max = 50.6 +/- 0.8 ml x kg(-1) x min(-1)) completed three 1-hour hyperthermic (ambient temperature = 38.7 +/- 1.0 degrees C, relative humidity = 33 +/- 4%) exercise sessions at 181 +/- 12 W (50% of Wmax, approximately 66% of VO2max). Subjects completed a baseline (BL) session, then 2 sessions following 5 days of CR (20 g x d(-1)) and placebo (PL, 20 g x d(-1)) administered in a double-blind counterbalanced crossover manner with > or = 28-day washout. Pre-exercise BL, CR, and PL body mass were unchanged, with similar decreases in postexercise mass among the three conditions. Tympanic temperature, heart rate, systolic blood pressure, perceived exertion, and lactate, cortisol, and aldosterone concentrations increased similarly during BL, CR, and PL exercise. A greater (p = 0.013) estimated decrease in plasma volume occurred following BL (-16.5 +/- 2.0%) and PL (-17.6 +/- 1.7%) exercise compared to CR (-13.5 +/- 2.1%). Creatine supplementation reduces plasma volume loss during 1 hour of hyperthermic exercise but does not appear to otherwise change thermoregulatory response to hyperthermic exercise.

Laboratory 20-km cycle time trial reproducibility

This study evaluated the reproducibility of laboratory based 20-km time trials in well trained versus recreational cyclists. Eighteen cyclists (age = 34 +/- 8 yrs; body mass index = 23.1 +/- 2.2 kg/m (2); VO(2max) = 4.19 +/- 0.65 L/min) completed three 20-km time trials over a month on a Velotron cycle ergometer. Average power output (PO) (W), speed, and heart rate (HR) were significantly lower in the first time trial compared to the second and third time trial. The coefficients of variation (CV) between the second and third trial of the top eight performers for average PO, time to completion, and speed were 1.2 %, 0.6 %, 0.5 %, respectively, compared to 4.8 %, 2.0 %, and 2.3 % for the bottom ten. In addition, the average HR, VO(2), and percentage of VO(2max) were similar between trials. This study demonstrated that (1) a familiarization session improves the reliability of the measurements (i.e., average PO, time to completion and speed), and (2) the CV was much smaller for the best performers.

Acurácia do teste de escada utilizando o consumo máximo de oxigênio como padrão-ouro

OBJETIVO: Determinar a acurácia dos atributos do teste de escada (TE) de altura definida utilizando como padrão-ouro o consumo máximo de oxigênio (VO2 máx). MÉTODOS: O TE foi realizado com incentivo, em escada (6 lances; 72 degraus; 12,16 m de altura total), em 51 pacientes. O 'tempo' de subida foi cronometrado e o 'trabalho' e a 'potência' calculados. O VO2 máx foi obtido por ergoespirometria, utilizando-se o protocolo de Balke. Foram calculados a correlação linear de Pearson (r) e os valores de p entre as variáveis do TE e o VO2 máx. Para o cálculo da acurácia, o ponto de corte do VO2 máx foi estabelecido em 25 mL/kg/min, estratificando os indivíduos em normais ou alterados. Os pontos de corte para os atributos do TE foram obtidos através da curva receiver operating characteristic. A estatística Kappa (k) foi utilizada para estudo da concordância. RESULTADOS: Obtiveram-se os seguintes valores para a variável 'tempo': ponto de corte = 40 s; x= 41 ± 15,5 s; r = -0,707; p < 0,005; especificidade = 89%; sensibilidade = 83%; acurácia = 86% e k = 0,724. Para a variável 'potência', obteve-se ponto de corte = 200 w; x= 222,3 ± 95,2 w; r = 0,515; p < 0,005; especificidade = 67%; sensibilidade = 75%; acurácia = 71% e k = 0,414. A correlação de 'trabalho' com o VO2 máx não foi significativa, sendo esse atributo descartado. CONCLUSÃO: Dos atributos testados do TE, tendo como padrão-ouro o VO2 máx, a variável 'tempo' foi a que apresentou a melhor acurácia.

The influence of circadian rhythm on muscle activity and efficient force production during cycling at different pedal rates

The aim of this study was to examine the pedal rate and chronobiological impacts on muscle activity pattern and propulsive force production during cycling. Ten male competitive cyclists performed at 06:00 and 18:00 h a submaximal exercise on a cycle ergometer at a power output which elicited 50% of their respective W(max). The exercise was divided into 4 periods lasting 5 min each during which subjects were requested to use different pedal rates (free pedal rate, 70, 90 and 120 rev min-1) in random order. The study demonstrated that, under high pedal rate, several muscles exhibited a phase advance of activity. These modifications of temporal organization of muscle activity were not sufficient to keep an identical propulsive torque pattern. Time to peak torque was delayed when pedal rate increased. The effects of circadian fluctuation on electromyographic activity were limited to a later M. rectus femoris burst end and shorter activity duration for M. tibialis anterior at 06:00 h. From the results of this study, it seems that the influence of pedal rate in the range of torque fluctuation would depend on time-of-day of testing. The decrease in torque fluctuation due to pedal rate increase is reinforced when testing in the early morning. Taking this specific variable into consideration, the chronobiological effect increases the impact of pedal rate variations.

Low-Frequency Rectangular Pulse Is Superior to Middle Frequency Alternating Current Stimulation in Cycling of People With Spinal Cord Injury

OBJECTIVE

To determine the efficacy of using modulated middle frequency alternating current (MFAC) muscle stimulation for functional electric stimulation-propelled cycling by people with spinal cord injury (SCI) compared with the conventional method of using standard low-frequency rectangular pulses (LFRP).

DESIGN

Repeated-measures.

SETTING

Laboratory setting.

PARTICIPANTS

Eleven otherwise healthy volunteer subjects with SCI (8 with American Spinal Injury Association [ASIA] grade A, 3 with ASIA grade B).

INTERVENTIONS

To evaluate cycling-relevant differences between LFRP and modulated MFAC stimulation, we exposed participants to isometric measurements and cycling experiments performed during both 20 Hz LFRP and 4 KHz modulated with 50 Hz MFAC.

MAIN OUTCOME MEASURES

We recorded maximal isometric torque, maximal dynamic work during 20 minutes of ergometer cycling, and perceived discomfort for each of the 2 stimulation patterns.

RESULTS

Both the isometric torque (P<.02) and work generated (P<.001) during MFAC stimulation were significantly lower than during standard LFRP stimulation. Four participants reported discomfort and 1 of them also developed skin burns during MFAC stimulation.

CONCLUSIONS

Our findings suggest that in SCI subjects, stimulated cycling with low frequency is generally more effective than cycling with modulated MFAC in terms of torque, work, and pain sensation.

Clinical condition at mid-to-late follow-up after transatrial-transpulmonary repair of tetralogy of Fallot

OBJECTIVES

To assess the clinical condition at mid-to-late follow-up in tetralogy of Fallot corrected by a transatrial-transpulmonary approach at a young age and to identify risk factors associated with right ventricular dilation/dysfunction and with decreased exercise tolerance.

METHODS

Patients with tetralogy of Fallot underwent cardiac magnetic resonance imaging, maximal bicycle ergometry, electrocardiography, Holter monitoring, and spirometry. Multivariate linear regression analyses were used to determine independent predictors for selected clinical parameters.

RESULTS

Fifty-nine patients (mean +/- SD), age at repair 0.9 +/- 0.5 years, interval since repair 14 +/- 5 years, were included. The median pulmonary regurgitant fraction was 32% (0%-57%). Compared with published data on healthy controls, Fallot patients had significantly larger right ventricular end-diastolic and end-systolic volumes and smaller right ventricular and left ventricular ejection fractions. Maximum oxygen consumption was 97% +/- 17% and maximum workload 89% +/- 13% of predicted. Median QRS duration was 110 ms (82-161 ms). No important ventricular arrhythmias were found. Compared with patients without a transannular patch, patients with a patch had more pulmonary regurgitation, a larger right ventricle, worse right ventricular and left ventricular ejection fractions, but comparable exercise capacity. Multivariate regression analysis identified the following independent determinants for larger right ventricular volumes: longer interval since repair, longer QRS duration, and higher pulmonary regurgitation percentage. The following were independent determinants for smaller right ventricular ejection fraction: abnormal right ventricular outflow tract wall motion, longer interval since repair, and longer QRS duration. For smaller maximum oxygen consumption, the independent determinants were smaller right ventricular ejection fraction and longer QRS duration.

CONCLUSIONS

At mid-to-late follow-up, clinical condition in tetralogy of Fallot corrected according to contemporary surgical approaches appears well preserved. However, even these patients show right ventricular dilation and dysfunction associated with impaired functional capacity. Abnormalities relate to right ventricular outflow tract motion abnormalities, longer interval since repair, longer QRS duration, and more severe pulmonary regurgitation.

High-intensity resistance training amplifies muscle hypertrophy and functional gains in persons with Parkinson's disease

Strength deficits in persons with Parkinson's disease (PD) have been identified as a contributor to bradykinesia. However, there is little research that examines the effect of resistance training on muscle size, muscle force production, and mobility in persons with PD. The purpose of this exploratory study was to examine, in persons with PD, the changes in quadriceps muscle volume, muscle force production, and mobility as a result of a 12-week high-force eccentric resistance training program and to compare the effects to a standard-care control. Nineteen individuals with idiopathic PD were recruited and consented to participate. Matched assignment for age and disease severity resulted in 10 participants in the eccentric group and 9 participants in the control group. All participants were tested prior to and following a 12-week intervention period with testing and training conducted at standardized times in their medication cycle. The eccentric group performed high-force quadriceps contractions on an eccentric ergometer 3 days a week for 12 weeks. The standard-care group exercise program encompassed standard exercise management of PD. The outcome variables were quadriceps muscle volume, muscle force, and mobility measures (6-minute walk, stair ascent/descent time). Each outcome variable was tested using separate one-way analyses of covariance on the difference scores. Muscle volume, muscle force, and functional status improvements occurred in persons with PD as a result of high-force eccentric resistance training. The eccentric group demonstrated significantly greater difference scores for muscle structure, stair descent, and 6-minute walk (P < 0.05). Magnitude of effect size estimators for the eccentric group consistently exceeded those in the standard-care group for all variables. To our knowledge, this is the first clinical trial to investigate and demonstrate the effects of eccentric resistance training on muscle hypertrophy, strength, and mobility in persons with PD. Additional research is needed to determine the anatomical and neurological mechanisms of the observed strength gains and mobility improvements.

Force-Velocity and Power-Velocity Relationships during Maximal Short-Term Rowing Ergometry

INTRODUCTION

Maximal rowing power-velocity relationships that exhibit ascending and descending limbs and a local maximum have not been reported. Further, duty cycle (portion of the stroke occupied by the pull phase) is unconstrained during rowing and is known to influence average muscular power output.

PURPOSE

Our purposes for conducting this study were to fully describe maximal short-term rowing force-velocity and power-velocity relationships. Within the context of those purposes, we also aimed to determine the apex of the power-velocity relationship and the influence of freely chosen duty cycle on stroke power.

METHODS

Collegiate varsity male rowers (N = 11, 22.9 +/- 2.3 yr, 84.1 + 12.1 kg, 184 +/- 7 cm) performed five maximal rowing trials using an inertial load ergometer. For each stroke, we determined force and power averaged for the pull phase and the complete stroke, instantaneous peak force and power, average handle velocity for the pull phase, handle velocity at peak instantaneous force and power, pull time, recovery time, and freely chosen duty cycle. Force-velocity and power-velocity relationships were characterized using regression analyses, and optimal velocities were determined from the regression coefficients.

RESULTS

Pull force-velocity (r2 = 0.99) and peak instantaneous force-velocity (r2 = 0.93) relationships were linear. Stroke power (r2 = 0.98), pull power (r2 = 0.99), and instantaneous peak power (r2 = 0.99) were quadratic, with apexes at 2.04, 3.25, and 3.43 m x s(-1), respectively. Maximum power values were 812 +/- 28 W (9.8 +/- 0.4 W x kg(-1)), 1995 +/- 67 W (23.9 +/- 0.7 W x kg(-1)), and 3481 +/- 112 W (41.9 +/- 1.3 W x kg(-1)) for stroke, pull, and instantaneous power, respectively. Freely chosen duty cycle decreased from 58 +/- 1% on the first stroke to 26 +/- 1% on the fifth stroke.

CONCLUSIONS

These data characterized the maximal rowing force-velocity and power-velocity relationships and identified the optimal velocity for producing maximal rowing power. Differences in maximum pull and stroke power emphasized the importance of duty cycle.

Effects of Levels of Cigarette Smoke Exposure on Symptom-Limited Spiroergometry

Previous investigations demonstrated reduced exposure to selected cigarette smoke constituents in adult smokers switching from conventional cigarettes (CC) to an electrically heated cigarette smoking system (EHCSS). This study investigated whether reduced exposure and no smoking (NS) would improve exercise performance. In a 3-period crossover study, 18 male adult smokers (age, 43.6+/-5.3 years) of CC were randomized to smoke CC (tar, 11 mg; nicotine, 0.8 mg; carbon monoxide, 11 mg), to use EHCSS (tar, 3 mg; nicotine, 0.2 mg; carbon monoxide, 0.4 mg [Federal Trade Commission method]), or to NS for 3 days before performing symptom-limited spiroergometry. NS and EHCSS vs CC resulted in less severe dyspnea (NS, 44.4% [P<.01 vs CC;] EHCSS, 50% [P=.03 vs CC;] CC, 88.9%), higher working capacity (NS, 2.92+/-0.4 W/kg [P=.06 vs CC;] ECHSS, 2.92+/-0.4 W/kg [P=.04 vs CC;] CC, 2.86+/-0.5 W/kg), higher peak oxygen uptake (NS, 2694+/-466 mL O(2)/min [P=.08 vs CC;] EHCSS, 2830+/-606 mL O(2)/min [P=.03 vs CC;] CC, 2682+/-492 mL O(2)/min), higher anaerobic threshold (NS, 1324+/-306 mL O(2)/min; EHCSS, 1396+/-312 mL O(2)/min [P=.03 vs CC;] CC, 1315+/-290 mL O(2)/min), and higher maximum rate-pressure product (NS, 30.1+/-2.7 x 10(3) mm Hg/min; EHCSS, 2.8 x 10(3) mm Hg/min [P<.01 vs CC;] CC, 30.7+/-29.2+/-3.6 x 10(3) mm Hg/min) indicating that reduced exposure from tobacco smoke and NS for 3 days may improve cardiovascular function as detected by symptom-limited spiroergometry.

Biventricular myocardial adaptation to different training protocols in competitive master athletes

BACKGROUND

Conflicting data have been reported about the nature (physiologic versus pathologic) of left ventricular (LV) hypertrophy in master athletes.

AIM OF THE STUDY

To analyze LV and right ventricular (RV) myocardial function in master athletes with LV hypertrophy induced by either endurance or strength training.

METHODS

Standard Doppler echo and colour Doppler Myocardial Imaging (DMI) of LV and of RV basal lateral walls were performed in 40 competitive master (>45 years) endurance athletes (ATE), in 20 master strength-trained athletes (ATS) and 25 age-matched healthy sedentary subjects, all males. By use of DMI, the following parameters of myocardial function were assessed: systolic peak velocities, precontraction time, contraction time, early (E(m)) and late (A(m)) diastolic peak velocities, E(m)/A(m) ratio, relaxation time.

RESULTS

The two groups were comparable for age, but ATS at rest showed higher heart rate, systolic blood pressure, and body surface area. LV mass index did not significantly differ between the two groups of athletes. However, ATS showed increased wall thickness and relative wall thickness, while LV stroke volume and both LV and RV end-diastolic diameters were greater in ATE. All transmitral and transtricuspid Doppler indexes were higher in ATE. DMI analysis showed in ATE higher E(m) and E(m)/A(m) ratio at the level of both RV and LV lateral walls. In the overall population of athletes, linear regression models evidenced independent positive association of RV peak E(m) velocity with both LV stroke volume and maximal workload achieved by bicycle ergometer (both p<0.001).

CONCLUSIONS

RV early diastolic myocardial function is positively influenced by preload increase in master athletes and represents an independent determinant of cardiac performance during physical effort. Therefore, colour DMI may be taken into account to distinguish different cardiac adaptation to either endurance or strength sport training in master athletes.

Analysis of swimming performance from physical, physiological, and biomechanical parameters in young swimmers

The purpose of this study was to examine the influence of the energy cost of swimming, body composition, and technical parameters on swimming performance in young swimmers. Twenty-nine swimmers, 15 prepubertal (11.9 +/- 0.3 years; Tanner Stages 1-2) and 14 pubertal (14.3 +/- 1.4 years; Tanner Stages 3-4) boys participated in the study. The energy cost of swimming (Cs) and stroking parameters were assessed over maximal 400-m front-crawl swimming in a 25-m swimming pool. The backward extrapolation technique was used to evaluate peak oxygen consumption (VO2peak). A stroke index (SI; m2 . s(-1) . cycles(-1)) was calculated by multiplying the swimming speed by the stroke length. VO2peak results were compared with VO2peak test in the laboratory (bicycle, 2.86 +/- 0.74 L/min, vs. in water, 2.53 +/- 0.50 L/min; R2 = .713; p = .0001). Stepwise-regression analyses revealed that SI (R2 = .898), in-water VO2peak (R2 = .358), and arm span (R2 = .454) were the best predictors of swimming performance. The backward-extrapolation method could be used to assess VO2peak in young swimmers. SI, arm span, and VO2peak appear to be the major determinants of front-crawl swimming performance in young swimmers.

The effect of repetitive arm cycling on post stroke spasticity and motor control

This study's aims were (1) to test whether training on an arm ergometer improves motor performance, and (2) to develop a technique to quantify individual muscle spasticity. Nine patients with a stabilized hemisyndrome (in average 22 months after ischemic stroke in the territory of middle cerebral artery) underwent a 3-week training on an arm ergometer, 5 days/week. The patients were tested one week before training, at training onset, at the end of training and 2 weeks after training. Spasticity was quantified by (1) the Ashworth Scale of the elbow flexors and extensors, (2) the maximum active extension of the biceps, and (3) the minimum torque on the lesioned side during arm cycling. The data were standardized, pooled and a 2-way ANOVA revealed a decrease of the spasticity by the training (p=0.076). Similarly muscle force was evaluated by the Rivermead Motorik Assessment, the Motricity Index and the cycling force, and the range of active movement as the sum of the angles at a maximum shoulder flexion, shoulder abduction, elbow flexion and elbow extension. The training increased the force (p<0.01) and also the range of motion (p<0.05) significantly. The patients confirmed the clinical relevance of the results. The spasticity index - the relation between the muscle activity modulation on the normal and lesioned side - was shown to be a useful tool in quantifying individual muscle spasticity. It was concluded that cycling on an arm ergometer is a useful tool for rehabilitation.

Acceptability of Power Variation during a Simulated Hilly Time Trial

We investigated the acceptability of power variation during a cycling time trial (TT) with simulated uphill and downhill sections. Seven cyclists first completed an 800-kJ self-paced TT on a simulated flat course. An 800-kJ TT course with four sections of uphill/downhill was then modeled. Each section involved 100 kJ of cycling up a simulated gradient of 5 % followed by 100 kJ of riding down a simulated gradient of - 5 %. Participants were required to complete this simulated course using two pacing strategies; (i) at a constant power equivalent to the mean power achieved during the initial TT, and (ii) increasing power by 5 % of mean power when traveling uphill (mean duration of each climb = 714 s) and decreasing power in the downhill sections (mean duration of each descent = 190 s), so that overall mean power was equivalent to that in (i). All participants maintained this variable power strategy during the first half of the TT, but two riders could not adhere to the power variations during the final 400 kJ. Nevertheless, mean +/- SD finish time for the variable power trial (3670 +/- 589 s) was significantly faster than that for the constant power TT (3758 +/- 645 s), the 95 % confidence interval for the percentage improvement being 0.4 to 4.3 %. Heart rate and lactate responses were highest in the initial self-paced TT and did not differ between the subsequent constant and variable power trials. Ratings of perceived exertion were also similar between trials. In our externally-valid TT, we found that some cyclists cannot fully adhere to a pacing strategy involving an approximate +/- 5 % variation in mean power in parallel with gradient variation. Nevertheless, an important time saving can still result even if a variable pacing strategy is only partially adopted during a hilly time trial, so that no additional physiological strain is incurred.

Recovery kinetics throughout successive bouts of various exercises in elite cyclists

PURPOSE

In the present study we investigated whether a high volume of cycling training would influence the metabolic changes associated with a succession of three exhaustive cycling exercises.

METHODS

Seven professional road cyclists (VO2max: 74.3 +/- 3.7 mL.min.kg; maximal power tolerated: 475 +/- 18 W; training: 22 +/- 3 h.wk) and seven sport sciences students (VO2max: 54.2 +/- 5.3 mL.min.kg; maximal power tolerated: 341 +/- 26 W; training: 6 +/- 2 h.wk) performed three different exhaustive cycling exercise bouts (progressive, constant load, and sprint) on an electrically braked cycloergometer positioned near the magnetic resonance scanner. Less than 45 s after the completion of each exercise bout, recovery kinetics of high-energy phosphorylated compounds and pH were measured using P-MR spectroscopy.

RESULTS

Resting values for phosphomonoesters (PME) and phosphodiesters (PDE) were significantly elevated in the cyclist group (PME/ATP: 0.82 +/- 0.11 vs 0.58 +/- 0.19; PDE/ATP: 0.27 +/- 0.03 vs 0.21 +/- 0.05). Phosphocreatine (PCr) consumption and inorganic phosphate (Pi) accumulation measured at end of exercise bouts 1 (PCr: 6.5 +/- 3.2 vs 10.4 +/- 1.6 mM; Pi: 1.6 +/- 0.7 vs 6.8 +/- 3.4 mM) and 3 (PCr: 5.6 +/- 2.4 vs 9.3 +/- 3.9 mM; Pi: 1.5 +/- 0.5 vs 7.7 +/- 3.3 mM) were reduced in cyclists compared with controls. During the recovery period after each exercise bout, the pH-recovery rate was larger in professional road cyclists, whereas the PCr-recovery kinetics were significantly faster for cyclists only for bout 3.

DISCUSSION

Whereas the PDE and PME elevation at rest in professional cyclists may indicate fiber-type changes and an imbalance between glycogenolytic and glycolytic activity, the lower PCr consumption during exercise and the faster pH-recovery kinetic clearly suggest an improved mitochondrial function.

Electromyographic and neuromuscular fatigue thresholds as concepts of fatigue

The aim of this study was to investigate the concepts of electromyographic (EMG) threshold (EMGT) by integrated EMG (iEMG) signals and neuromuscular fatigue threshold (NMFT) concepts in trained male athletes. Nine competitive national-level male rowers (21.8 +/- 4.4 years; 186.2 +/- 4.6 cm; 79.6 +/- 8.4 kg) took part in this investigation. Subjects were asked to participate in the graded exercise test to volitional exhaustion and 500-, 1,000-, and 2,000-m all-out rowing ergometer tests on a rowing ergometer. During all tests, oxygen consumption parameters, average power, and iEMG of the musculus vastus lateralis were recorded. The second ventilatory threshold (248.9 +/- 26.67 W) and EMGT (258.89 +/- 27.13 W) were not significantly different but were significantly lower than the NMFT (302.25 +/- 45.10 W). During 1,000- and 2,000-m all-out distances, VO(2) increased during the first minute and then leveled on a plateau with a slight decrease at the end of the exercise. Vastus lateralis activity showed a slight increase during all distances that was accompanied by a remarkable increase towards the end of the distance. All measured threshold values were significantly correlated (r > 0.70; p < 0.05) to the rowing ergometer performance characteristics. It was concluded that EMGT is closely related to the aerobic-anaerobic transition phase, because NMFT represents the local fatigue accumulation in the muscle. NMFT indicates the performance capacity of the muscles; therefore, it helps coaches to better predict top athletes' performance.

The inadequate effect of automobile seating on foot posture and callus development

Driver posture is an important factor to be considered in the ergonomics design process of automobiles. Most decisions during automobile design and manufacture are informed by studying the intricate biomechanical components of human musculoskeletal systems to ensure maximum comfort, safety and well-being during driving. A case study is presented that confirms inappropriate foot position as a causative factor for the development of abnormal lateral/plantar heel callosities when driving a 4 x 4-style vehicle. The driver's foot position was influenced by the seat geometry of the vehicle. Cessation of driving the 4 x 4-style vehicle and driving of an alternative automobile while on holiday for a period of 4 weeks resolved the condition. On return to the 4 x 4-style vehicle, however, the abnormal callus patterns redeveloped while using the same footwear and no change in any other parameters. It is therefore suggested that seat and consequent foot position is an important ergonomic factor that should be addressed in the future design of automobile seating.

External work and peak power are reliable measures of ergometer grinding performance when tested under load, deck heel, and grinding direction conditions

The reliability of grinding performance was assessed in 18 current Emirates Team New Zealand America's Cup sailors in two test sessions separated by 5 h using a custom-built ergometer. Sixteen different grinding conditions that varied by load (Light 39 N x m, Moderate 48 N x m, Heavy 68 N x m), deck heel (Flat 0 degrees control, Downhill 25 degrees, Uphill 25 degrees, Right 25 degrees, Left 25 degrees), and grinding direction (forwards, backwards) were assessed using peak power and external work over 5 s during maximal-effort 8-s grinds. Reliability statistics included the difference in mean (M(diff)), standard error of measurement (SEM), and intraclass correlation coefficients (ICC). External work (SEM = 1.6-6.9%; ICC = 0.91-0.99) was a more consistent performance measure than peak power (SEM = 1.3-9.6%; ICC = 0.84-0.99) across all test conditions. Testing under different load conditions resulted in external work SEMs of 1.6-3.9% with performance more reliable in lighter load conditions. Grinding performance during different heel conditions was less reliable (external work SEMs = 4.6-6.9%). Grinding direction (forward or backward) did not appear to affect performance reliability, although external work was 10-15% higher in forward grinding. Reliability is acceptable across various loads, but testing under different heel conditions may need some protocol development to allow the detection of smaller differences in performance.

The effects of hyperthermia and hypoxia on ventilation during low-intensity steady-state exercise

This study assessed whether the elevated sensitivity of ventilation to hypoxia during exercise is accounted for by an elevation of esophageal temperature (Tes). Eleven males volunteered for two exercise sessions on an underwater, head-out cycle ergometer at a steady-state rate of oxygen consumption (V̇o2) of ∼0.87 l/min (SD 0.07). In one exercise session, 31.5°C (SD 1.4) water held Tesat a normothermic level of ∼37.1°C, and in the other exercise session, water at 38.2°C (SD 0.1) maintained a hyperthermic Tesof ∼38.5°C. After a 30-min rest and 20-min warm-up, exercising participants inhaled air for 10 min [Euoxia 1 (E1)], an isocapnic hypoxic gas mixture with 12% O2in N2(H1) for the next 10 min and air again [Euoxia 2 (E2)] for the last 10 min. A significant increase in V̇Eduring all hyperthermia conditions (0.01< P < 0.048) was evident; however, during hyperthermic hypoxia, there was a disproportionate and significant ( P = 0.017) increase in V̇Erelative to normothermic hypoxia. This was the main explanation for a significant esophageal temperature and gas type interaction ( P = 0.012) for V̇E. Significant effects of hyperthermia, isocapnic hypoxia, and their positive interaction remained evident after removing the influence of V̇o2on V̇E. Serum lactate and potassium concentrations, as well as hemoglobin oxygen saturation, were each not significantly different between normothermic and hyperthermic-hypoxic conditions. In conclusion, the elevated sensitivity of exercise ventilation to hypoxia during exertion appears to be modulated by elevations in esophageal temperature, potentially because of a temperature-mediated stimulation of the peripheral chemoreceptors.

Plasma Protein Carbonyl Response to Increasing Exercise Duration in Aerobically Trained Men and Women

The purpose of this study was to determine the effect of aerobic exercise duration on plasma protein carbonyl concentrations, a marker of protein oxidation, in aerobically trained men and women. Eight men (age: 27 +/- 4 years, VO (2peak): 4.09 +/- 0.26 L x min (-1); mean +/- SD) and 7 women (age: 27 +/- 6 years, VO (2peak): 2.33 +/- 0.24 L x min (-1)) exercised on an electrically-braked cycle ergometer at 70 % VO (2peak) for 30, 60 or 120 minutes on three separate days. Plasma samples collected before and immediately, 30- and 60-minutes post-exercise were analyzed for protein carbonyls. Mean oxygen uptake was greater for men in all conditions (2.75 +/- 0.03 L x min (-1); 38 +/- 0.43 ml x kg (-1) x min (-1)) compared to women (1.57 +/- 0.03 L x min (-1); 24.1 +/- 0.47 ml x kg (-1) x min (-1)). Total work performed during the exercise sessions was also greater for men than for women during the 30 (368 +/- 11 versus 223 +/- 7 kJ), 60 (697 +/- 17 versus 423 +/- 18 kJ), and 120-minute conditions (1173 +/- 44 versus 726 +/- 28 kJ) (Mean +/- SEM). Although these comparisons were significant (p < 0.0001), sex differences in total work performed and mean VO (2) did not result in sex differences in protein carbonyls. However, a condition by time interaction was observed with greater post-exercise values following the 120-minute condition compared to both the 30- and 60-minute conditions. Protein carbonyl concentration was greatest immediately post-exercise for both men and women and generally declined in a linear trend through one hour of recovery. These data suggest that protein carbonyl concentration is elevated by cycling exercise performed at 70 % VO (2peak), is greater following longer duration rides, begins to recover within one hour following exercise, and is not different between men and women.

The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes

BACKGROUND

The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear.

AIMS

To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes.

METHODS

Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO(2)max) = 69.9 (7.9) (mlO(2)/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O(2)/65% N(2) (nitrox) or 35% O(2)/65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3-min intervals and at fatigue. Oxygen consumption (VO(2)) and minute ventilation (V(E)) were monitored continuously.

RESULTS

Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO(2)max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V(E) (157 (24) and 163 (22) l/min). Between-trial variability in peak power output was less than either VO(2)max or maximal V(E).

CONCLUSION

Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and V(E) with a concomitant reduction in VO(2) suggests an improved gas exchange and reduced O(2) cost of ventilation when breathing heliox.

Effectiveness of Low-Intensity Endurance Training

Recent studies point to the preventive efficacy of low-intensity endurance training in terms of cardiovascular risk factor modification and mortality reduction. In addition, it is frequently recommended as a means of stimulating fat metabolism. It was the intention of this study to clarify if endurance training effectiveness remains unimpaired when exercise intensity is reduced by a certain amount from "moderate" to "low", but total energy expenditure held constant. For this purpose, 39 healthy untrained subjects (44 +/- 7 yrs, 82 +/- 19 kg; 173 +/- 9 cm) were stratified for endurance capacity and sex and randomly assigned to 3 groups: "moderate intensity" (MOD, n = 13, 5 sessions per week, 30 min each, intensity 90 % of the anaerobic threshold [baseline lactate + 1.5 mmol/l]), "low intensity" (LOW, n = 13, 5 sessions per week, intensity 15 bpm below MOD, duration proportionally longer to arrive at the same total energy output as MOD), and control (CO, n = 13, no training). Training was conducted over 12 weeks and each session monitored by means of portable heart rate (HR) recorders. Identical treadmill protocols prior to and after the training program served for exercise prescription and documentation of endurance effects. VO (2max) improved similarly in both training groups (MOD + 1.5 ml x min (-1) x kg (-1); LOW + 1.7 ml x min (-1) x kg (-1); p = 0.97 between groups). Compared with CO (- 1.0 ml x min (-1) x kg (-1)) this effect was significant for LOW (p < 0.01) whereas there was only a tendency for MOD (p = 0.07). However, objective criteria (HR (max), maximal blood lactate) indicated that a different degree of effort was responsible for this finding. In comparison with CO (mean decrease of 3 bpm), average HR during incremental exercise decreased significantly by 9 bpm (MOD, p < 0.05 vs. CO) and 6 bpm (LOW, p = 0.26), respectively. However, there was no significant difference between MOD and LOW (p = 0.60), but for changes in oxygen uptake at the anaerobic threshold (VO (2AT)) it was observed that MOD was significantly more effective than CO (p = 0.048) and LOW (p = 0.04). It is concluded that within a middle-aged population of healthy untrained subjects, endurance training effectiveness might be slightly impaired when the training heart rate is chosen 15 bpm lower as compared to moderate intensity, but the total energy output held equal.

The ecological validity of laboratory cycling: Does body size explain the difference between laboratory- and field-based cycling performance?

Previous researchers have identified significant differences between laboratory and road cycling performances. To establish the ecological validity of laboratory time-trial cycling performances, the causes of such differences should be understood. Hence, the purpose of the present study was to quantify differences between laboratory- and road-based time-trial cycling and to establish to what extent body size [mass (m) and height (h)] may help to explain such differences. Twenty-three male competitive, but non-elite, cyclists completed two 25 mile time-trials, one in the laboratory using an air-braked ergometer (Kingcycle) and the other outdoors on a local road course over relatively flat terrain. Although laboratory speed was a reasonably strong predictor of road speed (R2 = 69.3%), a significant 4% difference (P < 0.001) in cycling speed was identified (laboratory vs. road speed: 40.4 +/- 3.02 vs. 38.7 +/- 3.55 km x h(-1); mean +/- s). When linear regression was used to predict these differences (Diff) in cycling speeds, the following equation was obtained: Diff (km x h(-1)) = 24.9 - 0.0969 x m - 10.7 x h, R2 = 52.1% and the standard deviation of residuals about the fitted regression line = 1.428 (km . h-1). The difference between road and laboratory cycling speeds (km x h(-1)) was found to be minimal for small individuals (mass = 65 kg and height = 1.738 m) but larger riders would appear to benefit from the fixed resistance in the laboratory compared with the progressively increasing drag due to increased body size that would be experienced in the field. This difference was found to be proportional to the cyclists' body surface area that we speculate might be associated with the cyclists' frontal surface area.

The repeatability of submaximal endurance exercise testing in cystic fibrosis

Submaximal endurance cycle ergometer exercise tests are used to measure the efficacy of an exercise intervention, but the repeatability of these tests in patients with cystic fibrosis (CF) has not been established. The purpose of this study was to examine the repeatability of submaximal endurance testing in stable CF. Fifteen adults with CF underwent two submaximal endurance tests carried out over a 7-day period. A subset of six subjects returned 28 days later for a third submaximal endurance test. Workload was set at 80% of maximum workload and exercise was performed to exhaustion. Oxygen consumption, minute ventilation, tidal volume, carbon dioxide output, respiratory rate, heart rate, and oxygen saturation were measured at rest, at end exercise and at four matched times during the submaximal endurance tests (20, 40, 60, and 80% of exercise duration calculated from the first endurance test). Submaximal endurance test time was highly repeatable with no significant learning effect identified on multiple testing. Submaximal endurance exercise time demonstrated a variability of 5.7% which is consistent with high levels of repeatability. Metabolic, ventilatory and cardiac variables were all also highly reproducible between test days. Submaximal endurance testing is repeatable in stable CF, confirming that submaximal endurance tests are a reliable tool for assessment of therapeutic benefit in patients with CF.

Influence of Nutrient Intake after Weigh-In on Lightweight Rowing Performance

PURPOSE

The aim of the present study was to compare the effectiveness of different nutritional recovery strategies between weigh-in and racing on 2000-m rowing ergometer performance among oarsmen undertaking short-term weight loss before competition.

METHODS

Competitive rowers (N = 12) completed four ergometer trials, each separated by 48 h. No weight restrictions were imposed for the first trial (TR1). Thereafter, athletes were required to reduce their body mass by 5.2% in the 24 h before trial 2 (TR2), again reaching this body mass before the final two trials (TR3 and TR4). Athletes were provided with one of three nutritional recovery strategies in the 2 h between weigh-in and racing in a counterbalanced fashion according to a Latin square design: fluid (2.8 kJ.kg(-1), 0.0 g.kg(-1) carbohydrate, 0.6 mg.kg(-1) sodium, 28.5 mL.kg(-1) fluid; FLU), carbohydrate/sodium (45.3 kJ.kg(-1), 2.2 g.kg(-1) carbohydrate, 32.9 mg.kg(-1) sodium, 7.2 mL.kg(-1) fluid; CHO), and a combination of water and carbohydrate/sodium (44.8 kJ.kg(-1), 2.3 g.kg(-1) carbohydrate, 33 mg.kg(-1) sodium, 28.5 mL.kg(-1) fluid; COM).

RESULTS

Performance was slower for CHO compared with both COM (mean difference, 4.13; 95% CI, 1.37-6.88 s; P = 0.003) and FLU (2.88; 95% CI, 0.13-5.63 s; P = 0.039). However, FLU was not significantly slower than COM (1.24; 95% CI, -1.41 to 3.90 s; P = 0.474).

CONCLUSIONS

The present investigation has shown that although carbohydrate and sodium intake may be important in the recovery period between weigh-in and 2000-m rowing ergometer performance, fluid intake has a greater influence on performance among lightweight male rowers who undertake short-term weight loss to achieve specified body-mass limits.

High Resistance / Low Repetition vs. Low Resistance / High Repetition Training: Effects on Performance of Trained Cyclists

In order to investigate the effects of a resistance training modality on cycling performance, 23 trained club-level cyclists were placed into high resistance/low repetition (H-Res), low resistance/high repetition (H-Rep), or cycling-only groups for a 10-week program. All 3 groups followed the same cycling plan, but the H-Res and H-Rep groups added resistance training. Testing pre and post consisted of a graded incremental lactate profile test on an ergometer, with blood lactate being sampled. VO2 values were measured to determine economy. Maximum strength testing of 4 strength exercises targeting the lower extremity musculature was conducted with the H-Res and H-Rep groups. There were significant gains in all 4 resistance training exercises (p < 0.05) for both H-Res and H-Rep, with the H-Res group having significantly greater gains than the H-Rep group had in the leg press exercise (p < 0.05). There were, however, no significant group x training differences (p > 0.05) found between the 3 training groups on the cycling test in lactate values or economy. It appears that for this population of cyclists, neither H-Res nor H-Rep resistance training provided any additional performance benefit in a graded incremental cycling test when compared with cycling alone over a training time of this length. It is possible that with this population, various factors such as acute fatigue, strength, and aerobic gains from the cycling training, in addition to well-developed bases of strength and conditioning from previous training, reduced differences between groups in both strength gains and cycling performance.

Upper-Extremity Exercise Training in Heart Failure

PURPOSE

Aerobic exercise training (ExTR), predominantly performed with lower extremities, has been used to reverse heart failure (HF)-related exercise intolerance. The present study determined the safety and efficacy of upper-extremity exercise in HF subjects because daily activities are performed using both upper and lower extremities and there is little cross-training effects between extremities.

METHODS

Seven subjects underwent 36 sessions (40 minutes, 3 times per week for 12 weeks) of upper-extremity ExTR (ARM ExTR) using arm ergometers, the arm function of a NuStep device, and an Airdyne stationary cycle. Exercise intensity and duration during weeks 1 to 4 were gradually increased to achieve a 75% to 85% peak heart rate. Pre- and post-ExTR tests included arm ergometer cardiopulmonary testing with echocardiography and quality of life self-administered surveys.

RESULTS

After ARM ExTR test duration increased by 22% (P = .008), respiratory exchange ratio increased by 10% (P = .02), whereas peak oxygen consumption was not improved. Echocardiographic parameters were not altered by ARM ExTR. The total scores of both the Minnesota Living With Heart Failure Questionnaire (P = .02) and the Medical Outcomes Study-36 questionnaire (P = .05) were improved, but the Functional Status Questionnaire scores were not improved.

CONCLUSIONS

Although this study was limited in the number of subjects and lacked a control group, results indicate that ARM ExTR is safe and well-tolerated by persons diagnosed with HF, a finding that is relevant for individuals with HF who cannot exercise with lower extremities.

A comparison of visual and mathematical detection of the electromyographic threshold during incremental pedaling exercise: a pilot study

During exhaustive incremental pedaling exercises, root mean square or amplitude of integrated electromyographic values exhibits a nonlinear increase, i.e., the so-called electromyographic threshold (EMG(Th)). As proposed by various authors, this EMG(Th) could be used as a complementary indicator of the aerobic-anaerobic transition in physiological evaluations. However, most of these studies used visual detection for the EMG(Th) and to date no previous study has shown the reliability of this type of EMG(Th) detection. We aimed to compare a visual and a mathematical method for EMG(Th) detection in each of 8 lower limb muscles during incremental cycling exercise. Our results showed an overestimation in the number of cases in which EMG(Th) was detected when using visual inspection (n = 45) compared with the mathematical method (n = 32). However, no significant differences were observed between the 2 methods concerning the power output at which EMG(Th) occurred. These results suggest that EMG(Th) should be mathematically detected. In this context, coaches can easily perform such measurements in order to evaluate the impact of their training programs on the neuromuscular adaptations of their athletes. For example, an automatic mathematical detection of EMG(Th) could be performed during a pedaling exercise in order to detect neuromuscular fatigue. Furthermore, this index could be used during test or training sessions performed either in a lab or in ecological situations. Moreover, the use of EMG(Th) to predict ventilatory threshold occurrence could be an interesting tool for trainers who cannot use the very expensive devices needed to analyze respiratory gas exchanges.

Physiological responses of skilled players during a competitive wheelchair tennis match

The purpose of this study was to determine heart rate (HR, b.min(-1)) response during competitive match play of 6 men who were skilled wheelchair (WC) tennis players. Each participant completed an arm crank ergometer test that measured HR via a telemetry device and O2 via open circuit spirometry from rest until fatigue (.V(O2)peak). Each athlete participated in 2 competitive singles matches during which HRs were recorded in 5-second intervals and O2 was estimated using the corresponding HR values recorded during the arm ergometer tests. Data analysis revealed an average playing intensity of 69.4 +/- 8.9% of HRpeak and 49.9 +/-14.5% of .V(O2)peak. In conclusion, it is recommended that skilled adult WC tennis players perform off-court aerobic conditioning as part of their training program, because the intensity of a competitive WC tennis match is sufficiently high enough to stress the cardiovascular system.

Is cardiorespiratory fitness related to quality of life in survivors of breast cancer?

The purpose of this study was to investigate whether indices of cardiorespiratory fitness are related to quality of life (QOL) in women survivors of breast cancer. Using the European Organization for Research and Treatment of Cancer QLQ-30 questionnaire, we assessed the QOL of 16 participants (age, 50 +/- 9 years; body mass, 66.6 +/- 9.6 kg). All participants performed incremental cycle ergometer exercise to determine several indices of cardiorespiratory fitness (e.g., peak oxygen uptake [.V(O2)peak, in L.min(-1), ml.kg(-1).min(-1)]), peak power output (PPO, in W), PPO/ body mass (W.kg(-1), peak heart rate (HRpeak, b.min(-1), peak ventilation (VEpeak), and .V(O2) and heart rate (HR) at the ventilatory (VT) and respiratory compensation (RCT) thresholds. Relationships between QOL and variables were assessed using Spearman rank-difference correlation tests. A significant inverse relationship (p < 0.05) was found for QOL scores and values for age (years) and body mass (kg) ( = -0.53), %HRpeak@VT ( = -0.59) and %VEpeak@VT ( = -0.61). A significant positive relationship (p < 0.05) was found for QOL and PPO/body mass ( = 0.59) and HRpeak ( = 0.78), .V(O2)@RCT (ml.kg(-1.min(-1) ( = 0.51), power output (PO, expressed as either W or W.kg(-1) at RCT, and HR at RCT ( = 0.54). No other significant relationship was found between QOL and variables obtained from the tests. In conclusion, these findings highlight possible relationships between cardiorespiratory fitness and well-being in survivors of breast cancer. From a practical point of view, our data emphasize the need for this population to engage in programmed cardiorespiratory exercise training, mainly designed to improve VT and RCT. The improvement of both submaximal indices can have a beneficial effect on QOL.

Strength and speed characteristics of elite, subelite, and recreational young soccer players

The purpose of the present study was to compare maximal isometric force, force-time curve characteristics, pedaling rate, vertical jump, and sprint performance among young soccer players from different competition levels. Fifty-four (54) young soccer players were divided into three groups according to competition level: the elite group (n=18) consisted of soccer players from the national youth soccer team of Greece, the subelite group (n=18) consisted of youth soccer players who participated in the local championship, and the recreational group (n=18) consisted of recreational soccer players. All groups were evaluated for maximal isometric force, explosive force at 100 msec, peak force relative to body mass, rate of force development, squat and drop jump heights, 10 m sprint time, and pedaling rate. The elite group presented significantly (p < 0.05) higher maximal isometric force, vertical jump height, and pedaling rate, and lower 10 m sprint time in comparison with the subelite and recreational groups. No significant differences were observed in strength and speed characteristics between the subelite and recreational young soccer players. The findings of the present study suggest that the elite young soccer players can be distinguished from subelite and recreational young soccer players in strength and speed characteristics. These strength and speed measures can be used for strength and speed diagnosis, and for designing and evaluating training programs.

Aerobic and anaerobic correlates of multiple sprint cycling performance

The aims of this study were to examine (a) the relationship between maximal oxygen uptake (VO(2)max) and several performance indices of multiple sprint cycling; (b) the relationship between maximal accumulated oxygen deficit (MAOD) and those same performance indices; and (c) the influence of recovery duration on the magnitude of those relationships. Twenty-five physically active men completed a VO(2)max test, a MAOD test, and 2 maximal intermittent (20 x 5 seconds) sprint cycling tests with contrasting recovery periods (10 seconds or 30 seconds). Mean +/- SD for age, height, and body mass were 20.6 +/- 1.5 years, 177.2 +/- 5.4 cm, and 78.2 +/- 8.2 kg, respectively. All tests were conducted on a friction-braked cycle ergometer with subsequent data normalized for body mass. Moderate (0.3 < or = r < 0.5) positive correlations were observed between power output data and MAOD (range, 0.31-0.46; 95% confidence limits, -0.10 to 0.72). Moderate to large positive correlations also were observed between power output data and VO(2)max, the magnitude of which increased as values were averaged across all sprints (range, 0.45-0.67; 95% confidence limits 0.07-0.84). Correlations between fatigue and VO(2)max were greater in the intermittent protocol with 30-second recovery periods (r = -0.34; 95% confidence limits, 0.06 to -0.65). The results of this study reflect the complex energetics associated with multiple sprint work. Though the findings add support to the idea that multiple sprint sports demand a combination of speed and endurance, further longitudinal research is required to confirm the relative importance of these parameters.

Gastrocnemius and soleus muscle length, velocity, and EMG responses to changes in pedalling cadence

Several authors have shown different excitation patterns for soleus and gastrocnemius muscles in response to cadence manipulation during cycling. The purpose of this study was to examine gastrocnemius and soleus length and velocity change as a function of pedalling cadence to consider mechanisms underlying these excitation differences. Ten male and two female cyclists rode at five randomly assigned cadences (50, 65, 80, 95, and 110 rpm) at a nominal 200 W power output while EMG of the gastrocnemius and soleus and sagittal plane video were recorded. Joint-coordinate data for the knee and ankle were used with equations of Grieve et al. [Grieve D, Pheasant S, Cavanagh PR. Prediction of gastrocnemius length from knee and ankle joint posture, in: E. Asmussen, K. Jorgensen, editors. International Series on Biomechanics, vol. 2A, Baltimore: University Park Press; 1978. p. 405-412] to compute gastrocnemius and soleus length and velocity. Consistent with previous publications, gastrocnemius displayed a significant (p<0.05) increase in integrated EMG with increased cadence, whereas cadence had no significant effect on integrated EMG of the soleus. The ankle became significantly (p<0.05) more plantar flexed and reflected a reduced range of motion with increased cadence while the knee became significantly (p<0.05) less extended. Soleus decreased its range of motion by 29%, whereas gastrocnemius decreased its range of motion by 9%. In contrast, soleus increased its velocity range by 32% and gastrocnemius increased by 45%. These data show that with increased cadence gastrocnemius operated over a narrower range of operating lengths but at a higher range of shortening velocity than soleus. The higher range of velocity may have resulted in the need for a relatively higher excitation, as indicated by the integrated EMG, as the muscle was working at a different range on its force-velocity curve. During the recovery portion of the pedalling cycle, the soleus was acting eccentrically while the gastrocnemius acted concentrically indicating the triceps surae complex did not always act in unison.

Non-random fluctuations in power output during self-paced exercise

OBJECTIVES

To analyse the power output measured during a self-paced 20-km cycling time trial, during which power output was free to vary, in order to assess the level and characteristics of the variability in power output that occurred during the exercise bout.

METHODS

Eleven well-trained cyclists performed a 20-km cycling time trial, during which power output was sampled every 200 m. Power spectrum analysis was performed on the power output data, and a fractal dimension was calculated for each trial using the Higuchi method.

RESULTS

In all subjects, power output was maintained throughout the trial until the final kilometre, when it increased significantly, indicating the presence of a global pacing strategy. The power spectrum revealed the presence of 1/f-like scaling of power output and multiple frequency peaks during each trial, with the values of the frequency peaks changing over the course of the trial. The fractal dimension (D-score) was similar for all subjects over the 20-km trial and ranged between 1.5 and 1.9.

CONCLUSIONS

The presence of an end spurt in all subjects, 1/f-like scaling and multiple frequency peaks in the power output data indicate that the measured oscillations in power output during cycling exercise activity may not be system noise, but may rather be associated with system control mechanisms that are similar in different individuals.

Glomerular Filtration Rate and Albumin Excretion After Maximal Exercise in Aging Sedentary and Active Men

BACKGROUND

From 30 years onwards there is a linear reduction of renal function of about 0.41% per year. Aging induces progressive impairment of glomeruli leading to an increase in protein excretion. The purpose of the present study was to investigate the effect of maximal exercise on glomerular filtration rate (GFR) and albumin excretion in an aging population.

METHODS

This is a cross-sectional study from 213 healthy men, sedentary or endurance-trained, aged 20-30 and 50-80 years submitted to maximal exercise on a cycle ergometer. Blood and urine samples were obtained at rest and after the strenuous exercise. We evaluated the GFR by measuring creatinine clearance and the urine albumin excretion rate.

RESULTS

After exercise, the older adults had a lesser reduction in GFR (mean 12%) than the young participants (mean 28%). As compared to those at rest, the increase of postexercise albumin excretion rates was lower in older participants (mean 7-fold) versus the young population (mean 20-fold). It appears that the exercise impact on some renal functions is related to the absolute load imposed on the individuals (r2 = 0.693).

CONCLUSION

As far as GFR and urine albumin excretion are concerned, regular endurance training does not induce any signs of potential incipient nephropathy in a healthy aging population.

The influence of ramp rate on VO2peak and "excess" VO2 during arm crank ergometry

The principal aim of this study was to examine how different ramp rates influenced the attainment of peak physiological responses during incremental arm crank ergometry (ACE). Additionally, the study examined whether there was any evidence for the development of an "excess" VO (2) during ACE due to upward curvi-linearity in the VO (2)-work rate relationship, and whether this was influenced by the ramp rate. Sixteen physically active, though non-specifically trained, men (mean +/- S age 30 +/- 8 years; height 1.79 +/- 0.07 m; body mass 84.7 +/- 13.2 kg) volunteered to participate. Having completed a familiarisation test, all subjects returned to the laboratory to complete two ramp tests on an electrically-braked ergometer in a counter-balanced order. Both ramp tests started at 60 W with work rate subsequently incremented by either 6 or 12 W . min (-1). Pulmonary gas exchange was measured breath-by-breath throughout the tests. Subjects achieved a greater final work rate during the 12 W . min (-1) test compared to the 6 W . min (-1) test (168 +/- 28 vs. 149 +/- 26 W; p < 0.001). The VO (2peak) (3.06 +/- 0.65 vs. 2.96 +/- 0.48 L . min (-1); p = 0.27), HR (peak) (179 +/- 15 vs. 177 +/- 16 b . min (-1); p = 0.17) and V.E (peak) (112 +/- 22 vs. 105 +/- 16 L . min (-1); p = 0.09) were not different between the tests, but VCO (2peak) (3.54 +/- 0.64 vs. 3.27 +/- 0.46 L . min (-1); p = 0.01) RER (peak) (1.17 +/- 0.07 vs. 1.11 +/- 0.06; p < 0.001), and end-exercise blood (lactate) (11.9 +/- 2.1 vs. 10.8 +/- 2.6 mmol . L (-1); p = 0.005) were all higher in the 12 W . min (-1) test. An "excess" VO (2) was observed in 13 out of 16 tests at 12 W . min (-1) and in 15 out of 16 tests at 6 W . min (-1). Neither the magnitude of the "excess" VO (2) (0.42 +/- 0.41 vs. 0.37 +/- 0.18 L . min (-1); p = 0.66) nor the VO (2) at which the V.O (2)-work rate relationship departed from linearity (2.17 +/- 0.34 vs. 2.18 +/- 0.32 L . min (-1); p = 0.94) were significantly different between the two ramp tests. These data indicate that differences in ramp rate within the range of 6 - 12 W . min (-1) influence the peak values of work rate, VCO (2) and RER, but do not influence peak values of VO (2) or HR during ACE. The development of an "excess" VO (2) appears to be a common feature of ramp exercise in ACE, although the mechanistic basis for this effect is presently unclear.

Voluntary changes in leg cadence modulate arm cadence during simultaneous arm and leg cycling

Although there is some evidence showing that neural coupling plays an important role in regulating coordination between the upper and lower limbs during walking, it is unclear how tightly the upper and lower limbs are linked during rhythmic movements in humans. The present study was conducted to investigate how coupling of both limbs is coordinated during independent rhythmic movement of the upper and lower limbs. Ten subjects performed simultaneous arm and leg cycling (AL cycling) at their preferred cadences without feedback for 10 s, and then were asked to voluntarily change the cadence (increase, decrease, or stop) of arm or leg cycling. Leg cycling cadence was not affected by voluntary changes in arm cadence. By contrast, arm cycling cadence was significantly altered when leg cycling cadence was changed. These results suggest the existence of a predominant lumbocervical influence of leg cycling on arm cycling during AL cycling.

Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training

The onset of whole muscle hypertrophy in response to overloading is poorly documented. The purpose of this study was to assess the early changes in muscle size and architecture during a 35-day high-intensity resistance training (RT) program. Seven young healthy volunteers performed bilateral leg extension three times per week on a gravity-independent flywheel ergometer. Cross-sectional area (CSA) in the central (C) and distal (D) regions of the quadriceps femoris (QF), muscle architecture, maximal voluntary contraction (MVC), and electromyographic (EMG) activity were measured before and after 10, 20, and 35 days of RT. By the end of the training period, MVC and EMG activity increased by 38.9 +/- 5.7 and 34.8% +/- 4.7%, respectively. Significant increase in QF CSA (3.5 and 5.2% in the C and D regions, respectively) was observed after 20 days of training, along with a 2.4 +/- 0.7% increase in fascicle length from the 10th day of training. By the end of the 35-day training period, the total increase in QF CSA for regions C and D was 6.5 +/- 1.1 and 7.4 +/- 0.8%, respectively, and fascicle length and pennation angle increased by 9.9 +/- 1.2 and 7.7 +/- 1.3%, respectively. The results show for the first time that changes in muscle size are detectable after only 3 wk of RT and that remodeling of muscle architecture precedes gains in muscle CSA. Muscle hypertrophy seems to contribute to strength gains earlier than previously reported; flywheel training seems particularly effective for inducing these early structural adaptations.

Sampling period determination for heart rate logging under an exercise regimen

Using a mathematical procedure, we determine appropriate sampling rates for logging heart rate, at a variety of exercise intensities. The mathematical procedure involves correlating exercise and heart rate data to determine a dynamical mathematical model, from which the frequency response of the relationship between exercise intensity and heart rate can be determined. The sampling rate is then straightforwardly deduced by making appropriate measurements on the frequency response curve. We show how careful consideration needs to be given to the choice of dynamical model structure and the work regimen, so that consistent and convincing conclusions can be drawn. We demonstrate that the dynamics of the work-rate/heart-rate system are dependent on the nominal work/heart rate, but a 5-s sampling period, as used in many commercial heart rate monitors, appears to be adequate, especially when some averaging is performed before logging.

[The prevalence of low back pain and its relationship with household jobs and other factors in a group of women in a rural area in Manisa]

The aims of this cross-sectional study were to determine the prevalence of low back pain and to evaluate the effects of household jobs on low back pain in women living in a rural setting in Manisa. Study population is consisted of 302 women and cluster sampling is performed according to percentage of health center district populations. Participation ratio of this study was 89.1%. Univariete and multivariete risk approach in 95% confidence interval and t test were performed in data analysis. Brief Disability Questionnaire was applied to the study group. Life time and point prevalence of low back pain were determined 79.2% and 34.9% of the study group. Low back pain risk in 95 % CI was higher in wrong posture during ironing, heavy load lifting, overweight/obesity and disability 2.2 (1.1- 4.5), 4.5 (2.1-9.2), 3.8 (1.7-8.3) and 9.2 (4.3-19.7) times respectively. For preventive health measures it is necessary to apply ergonomic working conditions and to give appropriate postural habits to women.

Children's Pedometer-Determined Physical Activity during the Segmented School Day

PURPOSE

To describe the sex-specific patterns of school children's daily pedometer-determined physical (PA) during physical education (PE), recess and lunchtime, and before and after school.

METHODS

Eighty-one sixth-grade students (28 boys, age = 11.9 +/- 0.4 yr, BMI = 18.8 +/- 4.1 kg x m(-2); 53 girls, 11.8 +/- 0.5 yr, BMI = 20.2 +/- 4.6 kg x m(-2)) wore pedometers for four school days and were prompted to record steps accumulated at arrival and departure from school and during pre- and postrecess, lunchtime, and PE class.

RESULTS

Boys took significantly (P < 0.001) more steps per day than girls: 16,421 +/- 5,444 vs 12,332 +/- 3,056 steps per day, and more steps during release time (e.g., before-school Delta = 1289 steps, recess Delta = 479 steps, lunchtime Delta = 608 steps, and after-school Delta = 1872 steps) but the same number of steps during structured PE classes (1429 +/- 567 vs 1410 +/- 445 steps; P = 0.87). Lunchtime PA represented the most important source of daily PA (15-16%) obtained during school hours for both boys and girls, whereas recess accounted for 8-9% and PE class accounted for 8-11% of total steps per day. Regardless, almost half of daily steps taken are attributable to after-school activities.

CONCLUSION

These data provide greater understanding of sex-specific PA patterns and the relative contribution of distinct segments of the school day to school children's total PA.

Contribution of the Legs to Double-Poling Performance in Elite Cross-Country Skiers

PURPOSE

In the classical style of cross-country skiing, the double-poling (DP) technique, which is regarded as an upper-body exercise, is used on the flatter parts of a course. Limited biomechanical and physiological data are available about DP compared with other cross-country skiing techniques. The purpose of the present study was to evaluate the possible role of the lower body during DP.

METHODS

Eleven elite cross-country skiers performed two incremental tests using DP roller skiing at 1 degree inclination on a treadmill with or without locking the knee and ankle joints (DPLOCKED and DPFREE). Maximal and peak oxygen uptake (VO2max and VO2peak) during classic diagonal skiing and DP, respectively, were measured. In addition, heart rate, blood lactate concentration, and maximal DP velocity (Vmax) were determined. Pole-ground reaction forces and joint angles (elbow, hip, knee, and ankle) were analyzed.

RESULTS

The skiers obtained 7.7% higher VO2peak, 9.4% higher Vmax, and 11.7% longer time to exhaustion during DPFREE compared with DPLOCKED (all P < 0.05). There was a higher heart rate and blood lactate concentration in DPLOCKED at submaximal stages (all P < 0.05), with no difference in oxygen consumption. At 85% Vmax, corresponding to approximately 81% VO2peak FREE, the differences in physiological variables were accompanied by a 13.6% higher poling frequency, a 4.9% shorter poling phase, 13.3% shorter recovery phase, and 10.9% lower relative pole force in DPLOCKED (all P < 0.05).

CONCLUSIONS

Movements of the knee and ankle joints are an integrative part in the skillful use of the DP technique, and restriction of the motion in these joints markedly affects both biomechanical and physiological variables, impairing DP performance.

Active Travel to School and Cardiovascular Fitness in Danish Children and Adolescents

PURPOSE

Active travel to school provides an opportunity for daily physical activity. Previous studies have shown that walking and cycling to school are associated with higher physical activity levels. The purpose of this study was to investigate whether the way that children and adolescents travel to school is associated with level of cardiovascular fitness.

METHODS

Participants were recruited via a proportional, two-stage cluster sample of schools (N = 25) in the region of Odense, Denmark as part of the European Youth Heart Study (EYHS). Nine hundred nineteen participants (529 children, age 9.7 +/- 0.5 yr; 390 adolescents, age 15.5 +/- 0.4 yr) completed a maximal cycle ergometer test to assess cardiorespiratory fitness (Wmax x kg(-1)). Mode of travel to school was investigated by questionnaire. Physical activity was measured in 531 participants using an accelerometer. Regression analyses with robust standard errors and adjustment for confounders (gender, age, body composition (skinfolds), pubertal status, and physical activity) and the cluster sampling procedure were used to compare fitness levels for different travel modes. Multinomial logistic regression was applied to assess the odds for belonging to quartiles of fitness.

RESULTS

Children and adolescents who cycled to school were significantly more fit than those who walked or traveled by motorized transport and were nearly five times as likely (OR 4.8; 95% CI 2.8-8.4) to be in the top quartile of fitness.

CONCLUSION

Cycling to school may contribute to higher cardiovascular fitness in young people.

Changes in Blood Markers of Serotoninergic Activity Following High Intensity Cycle Ergometer Exercise

The purpose of this study was to measure concentrations of adrenaline (A), noradrenaline (NE), free tryptophan (f-Trp), prolactin (PRL), nonesterified fatty acids (NEFA), and blood lactate following 30 s of high-intensity cycle ergometer exercise. Adrenaline (A) and NE concentrations increased immediately postexercise (P < 0.05) and returned to levels observed at baseline 24 h later. Plasma f-Trp concentration decreased by 23.5% immediately following exercise (P < 0.05). There were no changes observed in serum concentrations of PRL. Plasma NEFA concentrations decreased immediately following exercise by 46% (P < 0.05) and returned to baseline values 24 h later. Whole blood lactate concentrations increased immediately post exercise (P < 0.05), and were higher than those measured 24 h later (P < 0.05). These findings indicate that blood markers of serotoninergic activity were unaltered by a single 30 s bout of maximal cycling.

Validation of a 24-h physical activity recall in indigenous and non-indigenous Australian adolescents

The purpose of this study was to evaluate the concurrent validity of a modified version of the widely used previous day physical activity recall (PDPAR-24) self-report instrument in a diverse sample of Australian adolescents comprising Aboriginal and Torres Strait Islanders (A&TSI) and non-indigenous high school students. A sample of 63 A&TSI and 59 non-indigenous high school students (N=122) from five public secondary schools participated in the study. Participants completed the PDPAR-24 after wearing a sealed electronic pedometer on the previous day. Significant positive correlations were observed between the self-reported physical activity variables (mean MET level, blocks of vigorous activity, and blocks of moderate-to-vigorous physical activity) and 24-h step counts. Validity coefficients (rho) ranged from 0.29 to 0.34 (p<0.05). A significant inverse correlation was observed for self-reported screen time and 24-h step count (rho=-0.19, p<0.05). Correlations for A&TSI students were equal to or greater than those observed for non-indigenous students. The PDPAR-24 instrument is a quick, unobtrusive, and cost-effective assessment tool that would be useful for evaluating physical activity and sedentary behaviour in population-based studies.

Effects of 28 days of beta-alanine and creatine monohydrate supplementation on aerobic power, ventilatory and lactate thresholds, and time to exhaustion

The effect of beta-alanine (beta-Ala) alone or in combination with creatine monohydrate (Cr) on aerobic exercise performance is unknown. The purpose of this study was to examine the effects of 4 weeks of beta-Ala and Cr supplementation on indices of endurance performance. Fifty-five men (24.5 +/- 5.3 yrs) participated in a double-blind, placebo-controlled study and randomly assigned to one of 4 groups; placebo (PL, n = 13), creatine (Cr, n = 12), beta-alanine (beta-Ala, n = 14), or beta-alanine plus creatine (CrBA, n = 16). Prior to and following supplementation, participants performed a graded exercise test on a cycle ergometer to determine VO(2peak), time to exhaustion (TTE), and power output, VO(2), and percent VO(2peak) associated with VT and LT. No significant group effects were found. However, within groups, a significant time effect was observed for CrBa on 5 of the 8 parameters measured. These data suggest that CrBA may potentially enhance endurance performance.

Physiological differences of elite and professional road cyclists related to competition level and rider specialization

AIM

The aim of this investigation was to study the physiological response to laboratory tests in elite and professional cyclists, and to relate it to the level at which riders compete and their specialization.

METHODS

A total of 71 cyclists were divided into two groups, elite and professional, and were assessed for physical measurements, a maximal graded test and a 30 s all-out test, both performed on a cycle ergometer. The sample included 24 uphill riders (UR), 32 flat terrain riders (FTR), 11 all terrain riders (ATR) and 4 sprinters (SP).

RESULTS

Professional riders showed significantly higher gross mechanical efficiency (GME) than their elite counterparts (25.6+/-2.6 vs 24.4+/-2%), but otherwise no other physiological differences emerged from the comparison between these two groups. However, many differences exist as a function of rider specialization, especially between UR and FTR. Compared with FTR, UR showed a higher VO2max (78.2+/-5.5 vs 72.6+/-6.5 mL x min(-1) x kg(-1)) and a lower maximal aerobic power (438.5+/-40.8 vs 465.3+/-36.2 W). From the 30 s all-out test, SP presents the highest maximal power (P < 0.05) and maximal velocity (P < 0.05) compared with all the other groups.

CONCLUSIONS

The results for GME indicate a better efficiency for professional riders and suggest the importance of technical aspects related to movement pattern in cycling. The sensitivity of the maximal graded test and the 30 s all-out test did not allowed other differentiations between elite and professional cyclists.

Non-invasive measurement of cardiac output: Evaluation of new infrared absorption spectrometer

The mass spectrometer (MS) traditionally has been the instrument of choice for measuring cardiac output (Q (T)) non-invasively using the foreign gas uptake method. However, the size and cost of the MS has hampered widespread adoption of this technique outside of the laboratory. Here, we present results, from six normal human subjects at rest and during exercise, of simultaneous Q (T) measurements by an MS and a new, portable infrared (IR) device developed in our laboratories. These measurements are made using on the open-circuit acetylene uptake method. The IR device measures inspired and end-tidal concentrations of acetylene, sulfur hexafluoride, and carbon dioxide by IR absorption spectroscopy with a 10-90% response time of 43 ms; accurate measurements were made down to sample flow rates of 50 mL min(-1). Excellent correlation [Q (T)(IR)=0.98 Q (T)(MS), R(2)=0.94] was observed between instruments across the range from rest to heavy exercise. These results suggest that the IR device, which is small, light-weight, and rugged may enable the foreign gas uptake method to be used in clinical, field, and point-of-care settings for Q (T) measurement.

Effects of vitamin E supplementation on oxidative stress at rest and after exercise to exhaustion in athletic students

AIM

The purpose of this study is to determine the effect following exercise to exhaustion of vitamin E supplementation on oxidative stress in athletic students.

METHODS

Twenty male students voluntarily participated in the study and were randomly assigned (double blind) to either a vitamin E (daily dose of 450 mg of a-tocopherol for a period of 8 weeks) or a placebo group (took capsules containing 450 mg of lactose for 8 weeks). Before and after 8 weeks blood samples were collected at rest and after exercise to exhaustion. Oxidative stress markers were malondialdehyde (MDA), carbonylated proteins (CP) and creatine kinase (CK). Also, the effect of vitamin E on ergometer cycling time, as an example of endurance performance, was evaluated.

RESULTS

ANOVA and independent t-tests indicated that vitamin E supplementation did not significantly change (P > 0.05) MDA, CP and CK values at rest, after exercise to exhaustion, and cycling time, but plasma volume after exercise to exhaustion significantly decreased (P < 0.05).

CONCLUSIONS

Although vitamin E supplementation had no effect on exercise performance or capacity in athletic students, further investigation is required using larger numbers of subjects and measures of vitamin E before unequivocal conclusion can be stated.