Influence of aerobic exercise with an intermission, using a bicycle ergometer, on fat metabolism in obese patients with gonarthrosis

Our study was conducted to acquire essential information on the fat metabolism of obese patients with gonarthrosis during aerobic exercise, with a bicycle ergometer, with an intermission and without an intermission. Two experiments were conducted. Six women with gonarthrosis participated in the first experiment and another six women with gonarthrosis participated in the second experiment. The first experiment was conducted to investigate the influence of the total programmed workload on fat metabolism during bicycle aerobic exercise, and the second was conducted to investigate the effect of an intermission on fat metabolism when exercise consisted of an equally distributed total 50-W workload. During the experiment three exercise patterns were tested (six training sessions, each with 5 min of aerobic bicycle exercise with of 5 min, three training sessions each with 10 min of exercise with intermissions of 5 min, and 30 min of continuous exercise). The first experiment revealed that there was a significant relationship between the increase in free fatty acids (FFA) after exercise and the workload (P < 0.05). The second experiment revealed that there was no significant difference in the increase of FFA among the three exercise patterns. Exercise that was undertaken at a 50-W workload had a negligible effect on the women's vital signs. The bicycle ergometer aerobic exercise with an intermission actually led to an increase in FFA values compared with the effects of the continuous aerobic exercise.

The reproducibility of estimates of critical power and anaerobic work capacity in upper-body exercise

The purposes of this study were to apply the linear power versus inverse of time relationship to high-intensity upper-body exercise and to assess the repeatability of the parameters critical power (CP) and anaerobic working capacity (AWC), using limits of agreement (Bland and Altman 1986). Sixteen active male subjects (aged 20-34 years), performed two sets of five constant-power exercises on an adapted cycle ergometer. There were no significant differences between mean estimates of CP [96 (16) W and 95 (17) W] and AWC [7457 (2011) J and 7608 (1684) J] from the first and second sets of bouts. Despite the lack of systematic bias, there was evidence of large random error. Ratio limits of agreement for time to exhaustion during constant-power exercises suggested that a repeat measurement might be expected in 95% of cases to be between 0.64 and 1.59 times the original measurement. The 95% limits of agreement for CP were -15 W to +17 W. The ratio limits of agreement for AWC suggest that in 95% of cases a repeat measurement might be between 0.57 and 1.67 times the original estimate. The results of this study suggest a poor repeatability of constant-power upper-body exercises to exhaustion, which may contribute to a poor repeatability of CP and AWC determined from the linear power versus inverse of time model.

Aerobic work capacity in elite wheelchair athletes: a cross-sectional analysis

OBJECTIVE

To give a descriptive analysis of aerobic capacity among elite wheelchair athletes in association with various personal characteristics and sprint or anaerobic capacity.

DESIGN

Sixty-eight wheelchair athletes who participated in the World Games and Championships for the Disabled were included. Parameters for aerobic capacity were evaluated in a standardized wheelchair exercise test on a computer-controlled wheelchair ergometer at the games. The ergometer setting was individually tuned according to standardized procedures.

RESULTS

Mean maximum power output was 72.2 +/- 36.7 W. Peak oxygen uptake showed similar strong variations among different subject groups. High values were seen in a group of six subjects with amputations. Results stressed that, apart from sex, functionality and training status had a strong influence on aerobic capacity. Anaerobic and aerobic capacity were strongly associated.

CONCLUSIONS

Functionality, training status, and sex are important determinants of aerobic capacity. The functional classification used at international sports events is represented in the data, and further study into the possible contribution of standardized exercise tests within the issue of classification must be considered. The use of standardized exercise tests for the evaluation of training and for rehabilitation progress must be advocated, with power output being an important outcome measure at the level of ability, whereas oxygen uptake represents outcome at the level of organ systems.

Consequence of feedback-based learning of an effective hand rim wheelchair force production on mechanical efficiency

OBJECTIVE

Investigation of the effect of visual feedback on effective hand rim wheelchair force production and the subsequent effect on gross mechanical efficiency.

DESIGN

Ten subjects in an experimental group and 10 subjects in a control group practised three weeks (3.wk(-1), i.e., a pre-test and 8 trials) on a computer-controlled wheelchair ergometer. Every trial consisted of two blocks of 4 min at 0.15 and 0.25 W.kg(-1) at 1.11 m.s(-1). On three trials an additional block at 0.40 W.kg(-1) was performed. The experimental group practised with and the control group practised without visual feedback on the effectiveness of force production.

BACKGROUND

In mechanical terms, the low gross mechanical efficiency of hand rim wheelchair propulsion may be the result of ineffective force production.

METHODS

During all trials oxygen uptake, power output, forces and torque on the hand rims were measured.

RESULTS

In comparison with the control group, the experimental group at trial 8 had a significantly more effective force production compared to the control group (90-97% vs. 79-83%, respectively), but showed a significantly lower mechanical efficiency (5.5-8.5% vs. 5.9-9.9%, respectively).

CONCLUSION

Findings indicate that the most effective force production from a mechanical point of view is not necessarily the most efficient way--in terms of energy cost-- from a biological point of view and that force direction is based on an optimization of cost and effect.

RELEVANCE

Learning a more effective force production by visual feedback is not useful for increasing the mechanical efficiency of hand rim wheelchair propulsion.

The effect of glucose ingestion on endurance upper-body exercise and performance

The physiological responses to glucose supplementation during arm crank exercise were investigated. Ten subjects of mean age 28 +/- 8 years; stature 180.8 +/- 6.5 cm; mass 82.7 +/- 11.5 kg, .VO(2) peak 3.10 +/- 0.50 l x min(-1) were tested on two occasions separated by a week. A 7.6% glucose drink or placebo was administered in a blind crossover design 20 min prior to exercise. Subject's arm cranked for 60 min at an exercise intensity of 65% .VO(2)peak followed by a 20 min performance test. Rate of ventilation, oxygen uptake, RER, heart rate and blood lactate demonstrated similar responses between trials throughout the course of the hour. The blood glucose concentrations at rest were similar between trials increasing after glucose ingestion to show a significant difference (p < 0.05) to the placebo trial at the onset of exercise, then returning to resting values after 20 min. The 20 min performance tests revealed that after glucose ingestion athletes achieved a greater mean distance of 12.55 +/- 1.29 km than in the placebo trial of 11.50 +/- 1.68 km (p < 0.05). In conclusion, the results showed that after one-hour of arm crank exercise, performance over a further twenty minutes was improved when glucose was ingested twenty minutes prior to exercise.

Plasma testosterone and cortisol responses to prolonged sculling in male competitive rowers

In this study, we examined anabolic and catabolic hormone responses to a single endurance rowing training session in 12 male competitive single scull rowers. A work intensity eliciting a blood lactate concentration of 4 mmol(-1) was determined on a rowing ergometer during an endurance rowing training session lasting about 2 h (7891+/-761 s; distance covered 22.6+/-2.5 km; heart rate 136+/-7 beats x min(-1); intensity 77.4+/-3.8% of anaerobic threshold; mean +/- s). Venous blood samples were obtained before and after on-water rowing. Cortisol, testosterone and sex hormone binding globulin were measured and free testosterone and the free testosterone: cortisol ratio calculated. Blood lactate concentration did not change significantly during training (from 1.7+/-0.4 to 1.9+/-0.4 mmol x l(-1)); however, body mass was reduced (from 82.0+/-10.8 to 80.6+/-11.2 kg) and was related to the distance covered (r = -0.75). The concentrations of cortisol and testosterone did not change significantly during rowing or in the first 2 h of recovery. Free testosterone was reduced in the first 2 h of recovery, but no significant changes were observed in the free testosterone: cortisol ratio. Immediately after rowing, the concentrations of cortisol (r = 0.49) and free testosterone (r = -0.58) were related to the distance covered. Our findings indicate that a prolonged low-intensity training session results in a similar anabolic and catabolic hormone stimulus for trained rowers.

The effect of level of spinal cord injury on shoulder joint kinetics during manual wheelchair propulsion

OBJECTIVE

The effects of spinal cord injury level on shoulder kinetics during manual wheelchair propulsion were studied.

DESIGN

Single session data collection in a laboratory environment.

METHODS

Male subjects were divided into four groups: low level paraplegia (n=17), high level paraplegia (n=19), C7 tetraplegia (C7, n=16) and C6 tetraplegia (C6, n=17). Measurements were recorded using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and wheelchair ergometer. Shoulder joint forces and moments were calculated using the inverse dynamics approach.

RESULTS

Mean self-selected propulsion velocity was higher in the paraplegic (low paraplegia=90.7 m/min; high paraplegia=83.4 m/min) than tetraplegic (C7=66.5 m/min; C6=47.0 m/min) groups. After covarying for velocity, no significant differences in shoulder joint moments were identified. However, superior push force in subjects with tetraplegia (C7=21.4 N; C6=9.3 N) was significantly higher than in those with high paraplegia (7.3 N), after covarying velocity.

CONCLUSIONS

The superior push force in the tetraplegic groups coupled with weakness of thoraco-humeral depressors increases susceptibility of the subacromial structures to compression.

RELEVANCE

Increased vertical force at the shoulder joint, coupled with reduced shoulder depressor strength, may contribute to shoulder problems in subjects with tetraplegia. Wheelchair design modifications, combined with strength and endurance retention, should be considered to prevent shoulder pain development.

Musculo-tendinous and joint elastic characteristics during elbow flexion in children

OBJECTIVE

The aim of the present research was to determine joint stiffness and musculo-tendinous stiffness in children.

BACKGROUND

No reliable data was available on differences in such parameters when comparing children and adults.

METHODS

Sinusoidal perturbations and quick-released movements were applied to the right elbow during flexion to determine joint stiffness and musculo-tendinous stiffness, respectively. For normalization purposes, stiffness indexes were calculated as the slope of the relationship between stiffness and torque.

RESULTS

Main results were that musculo-tendinous stiffness indexes obtained in children were similar to adult data deduced from the literature. On the other hand, joint stiffness indexes obtained in children were in the range 0.9-3.8 rad(-1) and were lower than those reported in the literature for adults (between 4 and 8.5 rad(-1)).

CONCLUSION

Since normalized musculo-tendinous stiffness is similar in children and in adults, it can be hypothesized that, during growth, increase in ability to produce force parallels elastic tissue development.

RELEVANCE

Stiffness parameters could be used, in the context of other functional tests, to characterize changes in muscle properties in neuromuscular disorders when elastic tissues are supposed to be altered.

Physiological and performance characteristics of male professional road cyclists

Male professional road cycling competitions last between 1 hour (e.g. the time trial in the World Championships) and 100 hours (e.g. the Tour de France). Although the final overall standings of a race are individual, it is undoubtedly a team sport. Professional road cyclists present with variable anthropometric values, but display impressive aerobic capacities [maximal power output 370 to 570 W, maximal oxygen uptake 4.4 to 6.4 L/min and power output at the onset of blood lactate accumulation (OBLA) 300 to 500 W]. Because of the variable anthropometric characteristics, 'specialists' have evolved within teams whose job is to perform in different terrain and racing conditions. In this respect, power outputs relative to mass exponents of 0.32 and 1 seem to be the best predictors of level ground and uphill cycling ability, respectively. However, time trial specialists have been shown to meet requirements to be top competitors in all terrain (level and uphill) and cycling conditions (individually and in a group). Based on competition heart rate measurements, time trials are raced under steady-state conditions, the shorter time trials being raced at average intensities close to OBLA (approximately 400 to 420 W), with the longer ones close to the individual lactate threshold (LT, approximately 370 to 390 W). Mass-start stages, on the other hand, are raced at low mean intensities (approximately 210 W for the flat stages, approximately 270 W for the high mountain stages), but are characterised by their intermittent nature, with cyclists spending on average 30 to 100 minutes at, and above LT, and 5 to 20 minutes at, and above OBLA.

Reference values for dynamic responses to incremental cycle ergometry in males and females aged 20 to 80

Interpretation of incremental cardiopulmonary exercise tests (CPET) might be enhanced by considering the simultaneous rates of change of certain key variables, e.g., Delta oxygen uptake/Delta work rate (Delta VO(2)/Delta WR), Delta heart rate/Delta VO(2) (Delta HR/Delta VO(2)), Delta ventilation/Delta carbon dioxide production (Delta VE/Delta VCO(2)), and the linearized Delta tidal volume/Delta VE (Delta VT/Delta lnVE) relationships. However, there are no published age- and sex-dependent reference values for these relationships that were appropriately obtained in randomly selected subjects. We therefore prospectively evaluated 120 sedentary individuals (60 male, 60 female, age 20 to 80 yr) who were randomly selected from more than 8,000 subjects, and submitted to standard ramp-incremental CPET on an electronically braked cycle ergometer. We found that sex and age significantly influenced several of the dynamic relationships, in addition to anthropometric attributes (p < 0.05). A comprehensive set of linear prediction equations is provided; the limits of normality (at the 95% confidence level) differed substantially from previous recommendations based on single discrete values. These data therefore provide a frame of reference for assessing the normalcy of the response profiles of four standard indices of metabolic, cardiovascular, and ventilatory function during rapidly incremental cycle ergometry in sedentary males and females up to 80 yr of age.

Interval training program on a wheelchair ergometer for paraplegic subjects

BACKGROUND

Various combinations of training intensity, duration and frequency are often proposed to people with spinal cord injuries in order to improve their fitness. However, no consensus about a specific training program has been reached for such a population.

OBJECTIVE

This study investigated the effects of a short interval training program specifically designed for patients with spinal cord injuries.

METHODS

Paraplegic men performed 30-min wheelchair ergometry three times per week, for 4 weeks. Maximal dynamic performance and endurance capacity were studied before and after the training program with an incremental test (10 W/2 min) until volitional fatigue and a constant work rate test, respectively. Cardiorespiratory responses were continuously studied during each of these tests.

RESULTS

Training induced significant improvement in maximal tolerated power (+27.9%), and in peak oxygen consumption ([VO2, +18.5%). After training the subjects were able to maintain the load applied during the constant test (total mechanical work +210.7%), for a significantly longer time. The heart rate, [VO2 and ventilation values observed when the volunteers ended their first constant load test were significantly higher (+10%, +10%, +40% respectively) than those obtained after a similar time period during the second constant load test which was performed after the training program.

CONCLUSION

After this short training period, with an appropriate combination of different types of training, duration, intensity and frequency exercises, we observed a significant improvement in the fitness level and endurance capacity of paraplegic subjects.

Wheelchair propulsion biomechanics: implications for wheelchair sports

The aim of this article is to provide the reader with a state-of-the-art review on biomechanics in hand rim wheelchair propulsion, with special attention to sport-specific implications. Biomechanical studies in wheelchair sports mainly aim at optimising sport performance or preventing sport injuries. The sports performance optimisation question has been approached from an ergonomic, as well as a skill proficiency perspective. Sports medical issues have been addressed in wheelchair sports mainly because of the extremely high prevalence of repetitive strain injuries such as shoulder impingement and carpal tunnel syndrome. Sports performance as well as sports medical reflections are made throughout the review. Insight in the underlying musculoskeletal mechanisms of hand rim wheelchair propulsion has been achieved through a combination of experimental data collection under realistic conditions, with a more fundamental mathematical modelling approach. Through a synchronised analysis of the movement pattern, force generation pattern and muscular activity pattern, insight has been gained in the hand rim wheelchair propulsion dynamics of people with a disability, varying in level of physical activity and functional potential. The limiting environment of a laboratory, however, has hampered the drawing of sound conclusions. Through mathematical modelling, simulation and optimisation (minimising injury and maximising performance), insight in the underlying musculoskeletal mechanisms during wheelchair propulsion is sought. The surplus value of inverse and forward dynamic simulation of hand rim stroke dynamics is addressed. Implications for hand rim wheelchair sports are discussed. Wheelchair racing, basketball and rugby were chosen because of the significance and differences in sport-specific movement dynamics. Conclusions can easily be transferred to other wheelchair sports where movement dynamics are fundamental.

[Fat loading test: biochemical criteria and informative value of the physical endurance assessment]

Biochemical criteria of the fat loading test (FLT) were established and the search for interrelations between FLT biochemical variables and physiological parameters of dynamic physical testing (bicycle ergometry) was conducted in the experiment with participation of male volunteers. Relative gain in glucose, triglycerides, total cholesterol concentrations in blood, atherogenicity factor and insulin decrease after 3-hr FLT and reduction in blood concentrations of total cholesterol, insulin, hydrocortisone and testosterone after 9-hr FLT were ranked as reliable criteria. Rise in blood glucose and decrease in blood insulin after 3-hr FLT, and decrease in serum testosterone after 9-hr FLT were found to have prognostic value. Correlation between the FLT biochemical variables and physiological parameters as well as the package of regression analysis equations allow prediction for physical endurance. Yet, analysis of the correlation suggested that desensitization to insulin of the cell membrane cells should be a pathogenic mechanism of physical endurance decrement.

Effects of heart-rate feedback on estimated cardiovascular fitness in patients with panic disorder

Psychological parameters that are believed to affect estimations of cardiovascular fitness were examined in patients with panic disorder and nonclinical controls. Fifty-four participants [panic disorder patients (n = 27) and age- and sex-matched nonclinical controls (n = 27)] completed a cycle ergometer test and were compared on the basis of estimated VO2 max. Participants were randomly assigned to experimental conditions in which they received heart-rate feedback or no feedback during the test. Patients with panic disorder exhibited lower VO2 max and decreased exercise tolerance (i.e., were more likely to discontinue the test) than nonclinical controls. Furthermore, individuals with high anxiety sensitivity (i.e., a fear of autonomic arousal), but not a panic disorder diagnosis per se, achieved significantly lower VO2 max when provided with heart-rate feedback. Moreover, diagnostic status interacted with levels of anxiety sensitivity to predict VO2 max. Patients with panic disorder display poorer cardiovascular fitness after controlling for anxiety and other factors that underestimate performance during fitness testing.

A field evaluation of monitor placement effects in VDT users

Appropriate visual display terminal (VDT) location is a subject of ongoing debate. Generally, visual strain is associated with higher placement, and musculoskeletal strain is associated with lower placement. Seeking resolution of the debate, this paper provides a comparison of results from previous lab-based monitor placement studies to recommendations and outcomes from viewing preference and neutral posture studies. The paper then presents results from a field study that addressed two outstanding issues: Does monitor placement in a workplace elicit postures and discomfort responses similar to those seen in laboratory settings? Results showed placements in the workplace elicited postures similar to those in lab studies. Additionally, preferred VDT location generally corresponded to the location in which less neck discomfort was reported, though that trend requires further investigation. Overall, there seems to be consistent evidence to support mid-level or somewhat higher placement, as a rule-of-thumb, considering preferred gaze angle and musculoskeletal concerns. However, optimal placement may be lower for some individuals or tasks.

The effect of handgrip position on upper extremity neuromuscular responses to arm cranking exercise

The purpose of this study was to determine if handgrip position during arm cranking exercise influences the neuromuscular activity of muscles biceps brachii (BB), lateral head of triceps brachii (TB), middle deltoid (DT), infraspinatus (IS) and brachioradialis (BR). Fifteen participants cranked an arm ergometer using three different handgrip positions (supinated, pronated, and neutral). Electromyographic (EMG) data were recorded from the aforementioned muscles, and relative duration of EMG activation and amplitude were quantified for the first and second 180 degrees of crank angle. EMG measures were analyzed with MANOVA and follow-up univariate procedures; alpha was set at 0.01. The relative durations of EMG activation did not differ between handgrip positions. Muscle IS exhibited 36% less amplitude in the supinated versus neutral handgrip position (second half-cycle), and muscle BR displayed 63% greater amplitude across cycles in the neutral versus supinated and pronated handgrip positions. The greater BR activity displayed in the neutral handgrip position may reflect its anatomical advantage as an elbow flexor when the forearm is in neutral position. Muscle IS exhibited less activity in the supinated position and may be clinically relevant if it allows arm cranking to occur without subsequent shoulder pain, which is often the aim of shoulder rehabilitation.

Mean power frequency and amplitude of the mechanomyographic and electromyographic signals during incremental cycle ergometry

The purpose of this investigation was to determine the relationships for mechanomyographic (MMG) amplitude, MMG mean power frequency (MPF), electromyographic (EMG) amplitude, and EMG MPF versus power output during incremental cycle ergometry. Seventeen adults volunteered to perform an incremental test to exhaustion on a cycle ergometer. The test began at 50 W and the power output was increased by 30 W every 2 min until the subject could no longer maintain 70 rev min(-1). The MMG and EMG signals were recorded simultaneously from the vastus lateralis during the final 10 s of each power output and analyzed. MMG amplitude, MMG MPF, EMG amplitude, EMG MPF, and power output were normalized as a percentage of the maximal value from the cycle ergometer test. Polynomial regression analyses indicated that MMG amplitude increased (P<0.05) linearly across power output, but there was no change (P>0.05) in MMG MPF. EMG amplitude and MPF were fit best (P<0.05) with quadratic models. These results demonstrated dissociations among the time and frequency domains of MMG and EMG signals, which may provide information about motor control strategies during incremental cycle ergometry. The patterns for amplitude and frequency of the MMG signal may be useful for examining the relationship between motor-unit recruitment and firing rate during dynamic tasks.

Increased vagal tone during winter in subsyndromal seasonal affective disorder

BACKGROUND

Seasonal affective disorder (SAD) is characterized by recurrent winter depression with summer remissions and/or hypomania. Further symptoms include hypersomnia, increased appetite, weight gain, fatigue, and social withdrawal, which may indicate autonomic changes during winter.

METHODS

Measurements of respiratory sinus arrhythmia, heart rate (HR), and skin conductance level (SCL) were taken from 32 participants in subsyndromal SAD and control groups (eight male and eight female subjects in each group) in autumn and winter to determine any change in autonomic function. Measures were taken at baseline and during two stressor tasks. Single determinations of blood pressure, sublingual temperature, depression, aerobic fitness, and body mass index were also measured at each session. Replication in a second data collection period over subsequent winter and spring periods was conducted with an additional 32 participants to extend the findings and to counterbalance order effects in testing. Data were combined to produce "winter" and "nonwinter" test periods and statistically corrected for testing order.

RESULTS

Respiratory sinus arrhythmia differences indicated that SAD subjects have increased vagal tone in winter. Both groups show a decrease for HR and increases for SCL and diastolic blood pressure in winter.

CONCLUSIONS

Seasonal affective disorder may show similarities with hibernation, and the results may indicate mechanisms different from those of nonseasonal depression.

Electromyographic and discomfort analysis of confined-space shipyard welding processes

This study examined muscle fatigue and discomfort in a confined-space welding operation at a shipyard. Surface electromyography (SEMG) was recorded from seven upper extremity and torso muscles of welders welding in a mock-up of the work environment. Following spectral transform of the SEMG data the percentage of the total signal power in the 10-30 Hz frequency band was compared over time during welding. For the conventional stick electrode welding process (SMAW) several muscles exhibited an increase in the percent of the total signal power in the low-frequency band. Fewer muscles exhibited this fatigue-related spectral density shift with a wire welding process (FCAW) the shipyard has considered adopting. This finding suggests that localized muscle fatigue may be reduced by a change to the wire welding process. Subjectively reported discomfort was generally low for both processes, but confirmed the finding that discomfort in the low back and shoulder regions is experienced in this welding operation.

Reliability of mean power recorded during indoor and outdoor self-paced 40 km cycling time-trials

The purpose of this study was to assess reliability of both indoor and outdoor 40 km time-trial cycling performance. Eight trained cyclists completed three indoor 40 km time-trials on an air-braked ergometer (Kingcycle) and three outdoor 40 km time-trials on a local course. Power output was measured for all trials using the SRM powermeter. Mean performance time across three indoor trials was 54.21 +/- 2.59 (min:sec) and was significantly different (P<0.05) to mean time across three outdoor trials (57.29 +/- 3.22 min:sec). However, there was no significant difference (P = 0.34) for mean power across three indoor trials (303+/-35W) when compared to outdoor performances (312 +/- 23 W). Within-subject variation for mean power output expressed as a coefficient of variation (CV) improved in both indoors and outdoors for trials 2 and 3 (CV = 1.9%, 95% CI 1.0 - 3.4 and CV = 2.1 %, 95 % CI 1.1 - 3.8) when compared to trials 1 and 2 (CV=2.1%, 95% CI 1.2-3.8 and CV=2.4%, 95% CI 1.3-4.3). These findings indicate that power output measured using the SRM powermeter is highly reproducible for both laboratory-based and actual 40 km time-trial cycling performance.

Exercise intolerance in mitochondrial myopathy is not related to lactic acidosis

In a double-blinded, placebo-controlled, crossover study in seven mitochondrial myopathy patients (MM), we investigated whether lowering of lactate with dichloroacetate (DCA) can improve exercise tolerance and oxidative capacity in MM. DCA lowered plasma lactate at rest and during exercise (from 10.5 +/- 2.0 to 5.0 +/- 1.6 mM; p = 0.005) but did not improve maximal work load or VO2 in cycle exercise or phosphorous magnetic resonance spectroscopy (31P-MRS)-assessed indices of muscle oxidative metabolism. This indicates that lactate acidosis is not the primary cause of exercise intolerance in MM.

N-acetylcysteine attenuates oxidative burst by neutrophils in response to ergometer rowing with no effect on pulmonary gas exchange

This study evaluated whether the reduction of the neutrophil oxidative burst by N-acetylcysteine improves pulmonary gas exchange during a six minute maximal ergometer row. Healthy trained oarsmen were double-blinded randomized to either N-acetylcysteine (6 g daily for three days) or placebo groups. As determined by the relative changes of the zymosan-stimulated luminol-enhanced chemiluminescence response, N-acetylcysteine suppressed the exercise-induced enhanced neutrophil oxidative burst response to rowing (-7 +/- 6% vs. 17 +/- 8%; P < 0.05). This was the case although the concentration of neutrophils remained similarly elevated above the pre-exercise level in both trials (to 5.4+/-0.5 vs. 5.9+/-0.6 x 10(9) cells x l(-1), respectively, P>0.05). In the placebo and N-acetylcysteine groups, pulmonary ventilation increased and the arterial CO2 partial pressure decreased to the same extent during exercise. Also, at the end of exercise the arterial O2 partial pressure (77 1 vs. 78+/-1 mmHg), haemoglobin O2 saturation (92 +/- 1% vs. 93 +/- 1%) and O2 uptake (5.0 +/- 0.2 vs. 4.9 +/- 0.21 x min(-1)) were not significantly affected by N-acetylcysteine. Equally, two hours after exercise, the pulmonary diffusion capacity was reduced by 7 +/- 2% below the pre-exercise with no significant influence of N-acetylcysteine. We conclude that the neutrophil oxidative burst to exercise does not influence pulmonary gas exchange during and after maximal rowing.

[Isokinetic concentric dynamometry of knee flexors and extensors in young male]

Objective. To investigate the effects of different moving speeds on isokinetic dynamometry of knee flexors and extensors, and to provide normative data for comparative purposes in strength evaluations. Method. Thirty healthy male were tested at 60, 180, and 240 deg/sec angular velocities using a REV9000 testing and rehabilitation system. Result. Both PT (peak torque) and PT/BW (peak torque/body weights) showed significant differences (P< 0.01, P< 0.05) between flexors and extensors, and declined significantly with increased speed (P< 0.001). Peak torque differences between dominant and nondominant knee (Di%) was 10%. TPT (time to peak torque) tended to decrease as moving speeds increased (P< 0.001). APT (angle of peak torque) were 50%-70% for quadriceps, and 32%-45% for hamstrings; H/Q (hamstrings peak torque/quadriceps peak torque) was 50%-60%; WF (work fatigue) was 65%. Conclusion. The results provided a reference for strength evaluations in space medicine and space physiology, especially under simulated weightlessness and microgravity.

Responses of blood hormones to the maximal rowing ergometer test in college rowers

BACKGROUND

The purposes of this study were to investigate the resting levels and the acute hormonal response of total testosterone (Ttot), free testosterone (Tfree), cortisol (C) and Tfree:C ratio to the 6-minute all-out rowing ergometer test. METHODS.

EXPERIMENTAL DESIGN

Cross-sectional study to investigate the responses of blood hormones to the maximal rowing ergometer test in college rowers.

PARTICIPANTS

Eight college level male rowers (22.0 +/- 2.8 yrs, 191.8 +/- 4.1 cm, 85.4 +/- 4.3 kg, BMI: 23.2 +/- 1.3 kg x m(-2)) took part in this investigation.

INTERVENTIONS

a graded exercise test at the intensities of 150, 200 and 250 W (6-minute each) and a 6-minute all-out test on a rowing ergometer (Concept II, Morrisville, USA) were performed at separate measurement sessions.

MEASURES

Heart rate (HR) was recorded at the end of each load during a graded exercise test. Individual physical working capacity of rowers was calculated at the maximum HR recorded during a 6-minute all-out test. Venous blood samples were obtained 3 minutes before and immediately after the 6-minute all-out test to determine the concentration of Ttot, Tfree, Tfree:C ratio, glucose and lactate (LA) in blood.

RESULTS

Mean power was 354.3 +/- 26.8 W and HR 190.9 +/- 5.1 beats x min(-1) during the all-out test. Mean blood LA concentration at the end of the all-out test was 13.4 +/- 1.44 mmol x l(-1). The all-out test on the rowing ergometer did not change significantly the concentration of Ttot (before: 17.54+/-4.34; after: 20.03 +/- 4.80 nmol x l(-1)), Tfree (before: 0.423 +/- 0.111; after: 0.436 +/- 0.112), C (before: 477.50 +/- 119.34; after: 477.63+/-132.51 nmol x l(-1)) and Tfree:C ratio (before: 0.922 +/- 0.282; after: 0.973 +/- 0.320 x10(-3)). The transformation of these hormone values to effect sizes (ES) demonstrated that all-out test only moderately (ES < 0.61) influenced these hormone levels. Significant relationships were observed between the resting levels of Ttot and Tfree, and mean power of the 6-minute all-out test (r = 0.65 and r = 0.86, respectively). There was a non-significant increase in the level of Ttot following the all-out rowing ergometer test which was significantly related to mean power (r = 0.73) and covered distance (r = 0.67).

CONCLUSIONS

The results suggest that there are no significant changes in hormone levels during a 6-minute all-out rowing ergometer test. However, rowing performance is positively related to the resting values of Ttot and Tfree, and the non-significant changes in Ttot level following a 6-minute all-out test.