Maximal exercise response of paraplegic wheelchair road racers.

The maximal metabolic responses of 11 paraplegic wheelchair road racers were evaluated with 2 wheelchair exercise protocols: increasing speed and increasing resistance. The maximal heart rates, minute ventilations and oxygen uptakes were similar for the 2 tests, indicating that either protocol is suitable for maximal wheelchair dynamometer exercise tests for groups. The resulting data were then compared to published data on maximal arm exercise by athletic and non athletic paraplegics and ambulatory males of the same age group. The combined mean values for both exercise tests of maximal oxygen consumption rate (VO2max = 37.4 ml/kg/min), minute ventilation (VE = 109.4 l/min), respiratory exchange quotient (RQmax = 1.18) and heart rate (187 beats/min) are in the mid range of reported data on wheelchair athletes. The mean RQ and heart rate values were similar to those achieved by ambulatory individuals performing maximal exercise tests. The mean VO2max of 37.4 ml/kg/min in our subjects is comparable to that achieved by sedentary ambulatory males of this age group. The data and the comparison to published data suggest several conclusions: in some parameters elite male paraplegic road racers have maximal values similar to those of ambulatory males, and in others they have maximal values substantially lower than might be expected; there is considerable variability among paraplegics in the metabolic responses to maximal exercise, most likely related to differences in cardiovascular fitness; and paraplegics can improve their cardiovascular fitness by training.     

Physical fitness of paraplegics in full wheelchair marathon racing

The wheelchair marathon is one of the most difficult sports for participants with much uncertainty regarding the security of the paraplegics. The physical fitness of paraplegics has been examined regularly since The Oita International Wheelchair Marathon (half marathon) was inaugurated (1981). A full marathon (42.195 km) was adopted at The 3rd Meeting (1983). The individual equations between heart rate (HR) and oxygen consumption VO2 were drawn from the preliminary test on the subjects who were expected to be among the top finishers in these races. VO2 during these races was indirectly estimated and showed a fairly low value (35.0 +/- 3.8 ml/kg/min in the full race, 32.7 +/- 6.3 ml/kg/min in the half race respectively) in comparison with able-bodied elite runners. However, the paraplegic participants had extremely high HR (171.6 +/- 20.5 beats/min, 168.1 +/- 9.8) continuously throughout the race. Though the ratio of active muscle mass of arms to legs in paraplegic athletes may approximate to near equal, paraplegic arms seem to exert physiologically and mechanically less efficient power. There were no significant differences in physical fitness between the full and the half marathon elite finishers. The cardiovascular function of paraplegic athletes may well be ranked among those of able-bodied athletes in their fitness. Full wheelchair marathon seems to be safe if it is held in an appropriate environment.     

Exercise capacity of untrained spinal cord injured individuals and the relationship of peak oxygen uptake to level of injury

Twenty spinal cord injured individuals were tested for maximal oxygen uptake (VO2 peak using a hysteresis brake wheelchair ergometer. The subjects were divided into 4 groups as follows: (a) quadriplegics (4 subjects); (b) untrained female paraplegics (5 subjects); (c) untrained male paraplegics (7 subjects); and (d) trained male paraplegics (4 subjects). The VO2 peak were analysed by a one way ANOVA and Fisher's LSD multiple comparisons. The F-ratio (50.93) was significant (p = less than 0.0001). Fisher's LSD post hoc multiple comparisons found the following differences: (a) quadriplegics were significantly lower than the untrained paraplegic females, untrained paraplegic males and trained paraplegic males; (b) untrained females were significantly lower than the untrained male paraplegics, and trained paraplegic males; (c) untrained paraplegic males were significantly lower than the trained male paraplegics. A Spearman Rho correlation was calculated using injury level and VO2 max for all the untrained SCI individuals. The correlation was 0.68 and had a significance level of 0.0019. The present study combined with the known research literature gives strong evidence that VO2 peak in the untrained SCI is highly related to level of injury.     

An exercise test to evaluate fitness for wheelchair activity.

The purpose of this study was to develop a wheelchair ergometer (WERG) test to evaluate fitness for manual wheelchair activity. Thirty able-bodied females participated in a progressive intensity, discontinuous test where exercise bouts were 4 min in duration interspersed with 5-min rest periods. Physiological responses of oxygen uptake (VO2), respiratory exchange ratio (R), net mechanical efficiency (ME), pulmonary ventilation (VO) and heart rate (HR) were determined during the final minute of exercise at power output (PO) levels of 30, 60, 90, 120 and 150 kpm/min. These responses were generally found to be linearly related to PO, however, net ME initially increased with PO and plateaued at approximately 11 per cent at 90 kpm/min. Criteria for fitness evaluation were based upon: (1) magnitude of physiological responses at each PO level; and (2) the maximal PO level completed.     

The 577X allele of the ACTN3 gene is associated with improved exercise capacity in women with McArdle's disease

We assessed the possible association existing between alpha-actinin-3 (ACTN3) R577X genotypes and the capacity for performing aerobic exercise in McArdle's patients. Forty adult McArdle's disease patients and forty healthy, age and gender-matched sedentary controls (21 men, 19 women in both groups) performed a graded test until exhaustion and a constant-load test on a cycle-ergometer to determine clinically relevant indices of exercise capacity as peak oxygen uptake (VO(2peak)) and the ventilatory threshold (VT). In the group of diseased women, carriers of the X allele had a higher (P<0.01) VO(2peak) (15.0+/-1.2 ml/kg/min) and a higher (P<0.05) oxygen uptake (VO(2)) at the VT (11.2+/-1 ml/kg/min) than R/R homozygotes (VO(2peak): 9.6+/-0.5 ml/kg/min; VO(2) at the VT: 8.2+/-0.7 ml/kg/min). No differences were found in male patients. In women with McArdle's disease, ACTN3 genotypes might partly explain the large individual variability that exists in the phenotypic manifestation of this disorder.     

The effects of arm cranking exercise and training on platelet aggregation in male spinal cord individuals

Platelet aggregation at rest and in responses to exercise and training were compared between spinal cord injured (SCI) individuals (N=5) and able-bodied subjects (N=7). All participants performed arm cranking exercise at 60-65% VO(2peak) for 30 min. Venous blood samples were obtained before and after sub-maximal exercise and measured for platelet aggregation using ADP and collagen. To assess the effects of arm cranking training, platelet aggregation was re-measured in all subjects at rest and in response to the sub-maximal arm cranking exercise after 12 weeks of individually supervised training programme. Before training, the resting mean values of platelet aggregation induced by ADP and collagen were not different (P>0.05) between SCI and able-bodied. However the SCI individuals, but not the able-bodied subjects, exhibited a significantly (P<0.05) higher maximal platelet aggregation induced by ADP and collagen following sub-maximal arm cranking exercise. Although VO(2peak) after training was significantly increased (P<0.05) in both groups, the resting mean values of platelet aggregation induced with ADP and collagen were not significantly different (P>0.05) from those observed before training and were not different (P>0.05) between SCI and able-bodied. Post-training, the SCI individuals, but not able-bodied individuals, exhibited a significant decrease (P<0.05) in platelet aggregation following sub-maximal arm cranking exercise and this occurred with both ADP and collagen. These results suggest that SCI individuals, but not normal subjects increase their platelet aggregation following sub-maximal arm cranking exercise. Furthermore, arm cranking training in SCI individuals, appears to diminish the percentage of platelet aggregation ex vivo.     

Arm crank versus wheelchair treadmill ergometry to evaluate the performance of paraplegics

The purpose of this investigation was to compare peak performance capabilities of male paraplegics with arm crank and wheelchair ergometry. Eleven male paraplegics (aged 26.0 +/- 4.5 year) with spinal lesions at levels ranging from T5 to L4 were assessed during arm cranking and while propelling a wheelchair on a treadmill. Subjects completed both tests in randomised order within a 1 week period with a minimum of 48 hours between tests. Based on the data analysis, peak VO2 for the treadmill and arm crank were not significantly different while HR values for the treadmill were significantly greater (P less than 0.05) when compared to arm crank. A regression analysis indicated that wheelchair treadmill peak VO2 values can be accurately predicted from arm crank peak VO2 (r = 0.74).     

Physiological responses to maximal exercise on arm cranking and wheelchair ergometer with paraplegics.

This study describes the responses of 20 paraplegic athletes (mean age: 26.8 +/- 1.6 years) to a continuous incremental workload test until exhaustion on an arm cranking ergometer (ACE) and on a wheelchair ergometer (WCE). Both ergometers used the same electromagnetic braking device allowing a fair comparison between results. Tests were conducted at a 24 hour interval at the same time of the day. Oxygen uptake (VO2), heart rate (HR), workload (W), blood pressure (BP), Borg index, and mechanical efficiency (ME) were measured at every minute during the effort and the cool down periods of both tests. The purpose of this study was to analyse the different responses obtained on ACE and on WCE during maximal effort by paraplegics, and also to determine which ergometer permits the higher ME. Results indicate that paraplegics reached the same max HR on ACE and on WCE (97% of the predicted max HR). The lack of significant difference (p less than 0.05) between ACE and WCE in terms of maximal values of VO2, VE and HR suggests that the subjects reached their maximal capacity on each test regardless of the type of ergometer. Nevertheless, W max (in Watts) was 26% higher on ACE than on WCE. Maximal ME values were respectively 16% and 11.6% on ACE and WCE. Results suggest that ergometers and protocol used in this study are appropriate to measure physiological responses of paraplegic athletes during arm cranking and wheelchair exercise without excessive or early arm fatigue.     

Altered brain wave activity in persons with chronic spinal cord injury

This study investigated brain wave activity associated with spinal cord injury (SCI). Electroencephalograms (EEG) were compared between 10 individuals with SCI and 10 age and sex matched able-bodied controls using a 64-channel EEG montage. SCI participants had chronic (>12 months) paraplegic clinically complete injuries. The 64 channels of EEG data were spread diffusely over the cortex and were compared for delta (2-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) wave components of the EEG frequency spectra. No significant magnitude or directional changes were found in the delta (2-4 Hz) or theta (4-8 Hz) wave frequency bands between these two groups. However, significant and consistent decreased alpha wave (8-13 Hz) and increased beta wave activity (13-30 Hz) were found in the SCI participants across the cortex compared to the able-bodied control group. These findings suggest that the SCI group have increased neural processing compared to the able-bodied individuals, which may be related to ongoing reorganization of brain structures following SCI.     

Exercise capacity, disability and leisure physical activity of subjects with multiple sclerosis

The purpose of the present study was to examine exercise capacity and its relationship to neurological disability as measured using the Expanded Disability Status Scale (EDSS) and to leisure physical activity in subjects with multiple sclerosis (MS). Thirty-four men and 61 women (mean age 44 +/- 6.7 years, mean disease duration 5.7 +/- 6.4 years) with mild to moderate disability (EDSS range 1.0-5.5) participated. They underwent an incremental exercise test on a leg cycling ergometer. Leisure physical activity was measured using a questionnaire. Peak oxygen uptake (VO2peak) in men was 27.0 +/- 5.2 mL/kg/min, and in women 21.7 +/- 5.5 mL/kg/min. The disability correlated inversely with the VO2peak both in men (r = - 0.50, P = 0.004) and in women (r = - 0.25, P = 0.05). No correlation between disease duration and VO2peak was found. In a multivariate regression analysis, neurological disability was confirmed as a predictor of VO2peak. No evidence of a relationship between leisure physical activity and VO2peak was found. A main finding was that disability and exercise capacity are inter-related, even in subjects who are not severely handicapped (84% had an EDSS of < 4.0). The level of disability should be taken into account in the planning of aerobic exercise programs for fully ambulatory MS subjects.     

Heart rate variability is altered following spinal cord injury

Spinal cord injury (SCI) patients are know to suffer from autonomic failure as a result of their injury. The magnitude of the dysautonomia resulting from such an injury is difficult to predict or characterize and, in varying degree, it impedes the recovery of physiological homeostasis. This study is intended to investigate the effectiveness of heart rate variability (HRV) analysis as a method of quantifying and characterizing autonomic function in patients with traumatic spinal myelopathy. HRV analysis was carried out in 13 male SCI patients (six tetraplegic, seven paraplegic) and 13 age-matched, able-bodied controls. Twenty-four hour ambulatory and sleep ECG tracings were obtained. Time domain, amplitude, and power spectral analyses were used to study HRV and autonomic function. Both tetraplegic (20±12 ms, mean ±SD) and paraplegic (22±8 ms) subjects demonstrated significant loss of low frequency 24-hour HRV compared to able-bodied controls (36±14 ms, p<0.05) and during sleep. This was interpreted as being consistent with predominantly sympathetic denervation uninfluenced by degree of physical activity. There were no significant differences between groups in parasympathetically mediated high frequency HRV. We conclude that HRV analysis is capable of distinguishing between SCI or able-bodied humans and among tetraplegic and paraplegic patients. Patterns of altered HRV may be useful in more completely characterizing or stratifying changes in physiology associated with injury level and may have diagnostic, prognostic, or therapeutic significance.     

ALTERED BRAIN WAVE ACTIVITY IN PERSONS WITH CHRONIC SPINAL CORD INJURY

This study investigated brain wave activity associated with spinal cord injury (SCI). Electroencephalograms (EEG) were compared between 10 individuals with SCI and 10 age and sex matched able-bodied controls using a 64-channel EEG montage. SCI participants had chronic (>12 months) paraplegic clinically complete injuries. The 64 channels of EEG data were spread diffusely over the cortex and were compared for delta (2–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), and beta (13–30 Hz) wave components of the EEG frequency spectra. No significant magnitude or directional changes were found in the delta (2–4 Hz) or theta (4–8 Hz) wave frequency bands between these two groups. However, significant and consistent decreased alpha wave (8–13 Hz) and increased beta wave activity (13–30 Hz) were found in the SCI participants across the cortex compared to the able-bodied control group. These findings suggest that the SCI group have increased neural processing compared to the able-bodied individuals, which may be related to ongoing reorganization of brain structures following SCI.     

Long-term intensive electrically stimulated cycling by spinal cord-injured people: effect on muscle properties and their relation to power output

Inactivity and muscular adaptations following spinal cord injury (SCI) result in secondary complications such as cardiovascular disease, obesity, and pressure sores. Functional electrically stimulated (FES) cycling can potentially reduce these complications, but previous studies have provided inconsistent results. We studied the effect of intensive long-term FES cycle training on muscle properties in 11 SCI subjects (mean +/- SEM: 41.8 +/- 2.3 years) who had trained for up to 1 hour/day, 5 days/week, for 1 year. Comparative measurements were made in 10 able-bodied (AB) subjects. Quadriceps maximal electrically stimulated torque increased fivefold (n = 5), but remained lower than in AB individuals. Relative force response at 1 HZ decreased, relaxation rate remained unchanged, and fatigue resistance improved significantly. Power output (PO) improved to a lesser extent than quadriceps torque and not to a greater extent than has been reported previously. We need to understand the factors that limit PO in order to maximize the benefits of FES cycling.     

Autonomic control of the heart and renal vascular bed during autonomic dysreflexia in high spinal cord injury

Autonomic function and hemodynamics were studied in nine spinal cord injured (SCI) subjects, at rest and during peripheral afferent stimulation, bladder percussion. Nine able-bodied subjects were studied for comparison during unstimulated conditions. Spontaneous baroreceptor reflex sensitivity was calculated from recordings of ECG and intraarterial blood pressure. An index of sympathetic activity was provided by measuring total body noradrenaline (NA) spillover by isotope dilution technique. Renal vascular resistance was calculated from PAH-clearance. SCI subjects had lower total body NA spillover (1011 ± 193 vs 2261 ± 328 pmol/min, P < 0.01), but similar baroreceptor reflex sensitivity and hemodynamics compared to able-bodied subjects at rest. In SCI group, during bladder percussion, mean arterial pressure increased (79 ± 5 vs 113 ± 8 mm Hg, P < 0.01), whereas heart rate was reduced during the first minute of the manoeuvre (62 ± 2 vs 56 ± 2 bpm, P < 0.05). Baroreceptor reflex sensitivity remained unchanged. Total body NA spillover and renal vascular resistance increased by 332 % (from 1004 ± 218 pmol/min, P < 0.05) and 55 % (from 0.078 ± 0.011 mmHg/ml/min, P < 0.05), respectively. SCI subjects demonstrated lower total body sympathetic outflow but normal baroreceptor reflex sensitivity at rest, suggesting a balanced autonomic output to the heart. Bladder percussion caused a substantial increase in renal vascular resistance and blood pressure, which was partly due to marked generalised sympathetic activation. This activation was counterbalanced by an increased vagal activity as evidenced by reduction of the heart rate. Received: 6 March 2002, Accepted: 28 August 2002 Correspondence to Sinsia A. Gao, MD     

The effects of an arm ergometer training programme on wheelchair subjects

The purpose of the present investigation was to study the effects of an arm ergometer training programme on several physiological variables of recreational wheelchair subjects. Ten paraplegics (5 experimental, 5 control) were tested prior to and immediately after a 2 month exercise regimen at 80% of peak heart rate (30 min per day, 5 days per week, for 8 consecutive weeks at 50 rev/min). The results demonstrated significant increases (P less than 0.05) in VO2max (1 min-1 & ml kg-1 min-1) and workload but only mild improvements in maximal heart rate and post exercise blood lactates. Body fat, vital capacity and forced expiratory volume did not change with training. Triceps lateralis fibre distribution and fast twitch (FT) fibre area were unaffected by the endurance training programme. However, slow twitch (ST) fibre area increased (P less than 0.05) with training. The results indicate that physiological variables of paraplegic subjects following an arm ergometer endurance training programme react similarly to changes previously observed in non-handicapped subjects. The values when compared with normals are low as a result of the relative inactivity of the subjects due to the lack of available exercise programmes for wheelchair people.     

Self-actualisation of elite wheelchair athletes

The purpose of this study was to examine the self-actualisation of male and female elite wheelchair athletes in comparison to the general population and to able-bodied athletes. All subjects completed the Personal Orientation Inventory (POI), and statistically significant differences were identified. In general, wheelchair athletes were similar to the general population. Male wheelchair athletes were significantly more self-actualised than able-bodied athletes, but female wheelchair athletes were self-actualised to the same extent as able-bodied athletes.     

Comparisons of oxygen metabolism and tissue PO2 in cortex and hippocampus of gerbil brain

Recessed oxygen microelectrodes (tip diameter less than 2 microns) were positioned stereotactically into either the cerebral cortex or the hippocampus of sodium pentobarbital anesthetized gerbils (n = 21). The mean tissue PO2 levels (+/- SEM) were not significantly different between cortex (35.4 +/- 1.7 torr) and hippocampus (33.6 +/- 1.4 torr) although differences in the tissue PO2 distributions were seen. The disappearance rate for oxygen (-dPO2/dt) was measured after brief (less than 15 seconds) bilateral carotid artery (total brain blood flow) occlusion. The mean (+/- SEM) disappearance rate was significantly higher (p less than 0.05) in the cortex (23.8 +/- 1.5 torr/sec, 160 locations in 21 gerbils) than in the hippocampus (17.0 +/- 0.7 torr/sec, 119 locations in 16 gerbils). The maximum oxygen consumption rates (VO2max) for Michaelis-Menten kinetics were calculated from the disappearance rates, correcting for gerbil oxyhemoglobin. The mean VO2max was 8.28 +/- 0.51 and 6.13 +/- 0.25 ml O2/100 g/min for the cortex and hippocampus, respectively. The apparent Michaelis-Menten kinetic constants (Km) for the 2 regions were not significantly different (overall mean 3.3 +/- 0.4 torr). Differences in the recovery of tissue PO2 after releasing the occlusion were seen, with more hyperemic responses in the hippocampus.     

Metabolic responses of women to exercise attributable to long term use of a manual wheelchair

The purpose of this study was to determine the effects of long term use of a manual wheelchair by wheelchair-confined women (means = 14.6 years) on physiological responses to wheelchair ergometry. Six experimental subjects were compared to six able bodied women during maximal exercise as well as submaximal wheelchair ergometry at 50 and 80% of peak VO2. The wheelchair dependent women achieved higher power outputs, greater efficiency at the higher submaximal workload, less metabolic acidosis during submaximal exercise as well as less ventilatory stress. There was no significant difference in peak VO2 between the two groups of women. Because these were not athletically trained women, it was concluded that the long term use of a manual wheelchair leads to physiological adaptations favourable to the daily requirements of wheelchair locomotion.     

Monitoring of ventilation during the early part of cardiopulmonary exercise testing: the first step to detect central sleep apnoea in chronic heart failure

BACKGROUND AND PURPOSE: To evaluate the prediction of nocturnal central sleep apnoea (CSA) syndrome from the presence of periodic breathing (PB) on diurnal monitoring of pre-exercise (cardiopulmonary exercise test [CPX]) parameters. CSA syndrome is commonly found in congestive heart failure (CHF) patients and has several prognostic and therapeutic implications but is frequently undiagnosed. Awake PB pattern is sometimes observed during the CPX cardiopulmonary monitoring period of gas exchanges in CHF patients referred to the stress test laboratory for routine peak VO2 determination. PATIENTS AND METHODS: Forty-five consecutive ambulatory patients (2 women/43 men; 60.2+/-11.7 years old) with clinically moderate to severe CHF (New York Heart Association [NYHA] class II/III: 22/23; mean+/-standard deviation left ventricular ejection fraction [LVEF]: 30.5+/-6.6%) underwent a classical maximal CPX test including a 2-min period (pre-test) of gas exchange monitoring and nocturnal ambulatory polygraphic monitoring. PB was defined when a cyclical pattern of VE, VO2, VCO2, was visually noted during the pre-exercise period and/or during the first 4 min of the CPX. CSA syndrome was retained as a central apnoea-plus-hypopnea index (cAHI) equal to or more than 10/h. The sleep study scoring procedure was done independently of the knowledge of the CPX results. Sensitivity, specificity and predictive values were calculated and receiver operating characteristic (ROC) curve analysis was constructed. RESULTS: Peak VO2 reached 16.4+/-5.2 mL kg(-1)min(-1) (55% of the theoretical value adjusted for gender and age). The polygraphy was completed and validated (at least five consecutive hours of sleep) in all cases. CSA syndrome was found in 28 (62%) patients (mean cAHI: 19.3+/-8.6/h). Sensitivity for the prediction of CSA syndrome reached 92.9% (two false-negative patients with a cAHI of nine) and specificity 94.1% with a predictive accuracy of 93.3%. The only false-positive patient suffered a moderate but significant obstructive sleep apnoea syndrome. Using ROC curve analysis, the W value reached 0.99 for the prediction of CSA from the presence of PB. The presence of CSA syndrome, using logistic regression analysis, is associated with a more severe functional status (NYHA: p<0.01, peak VO2: p<0.002), a lower basal and peak end-expiratory CO2 pressure (PETCO2, all p<0.03), a worse LVEF (p<0.01) and age equal to or more than 60 years (p<0.03). CONCLUSIONS: The observation of PB in the preliminary period of the CPX test in CHF patients appeared highly predictive of the presence of CSA syndrome during sleep and could prompt the use of polygraphic monitoring in severe CHF patients.     

Exercise intensity: platelet function and platelet-leukocyte conjugate formation in untrained subjects

INTRODUCTION: Strenuous and exhaustive exercise intensifies platelet activity as shown in the literature but effects of moderate exercise are still in discussion. The present study investigated effects of two different standardised exercise intensities controlled by individual anaerobic threshold (IAT) on platelet function and conjugate formation. METHODS: 20 healthy male non-smokers underwent two exercises at 80% (moderate) of IAT which corresponded to about 57% of peak oxygen consumption (peak VO(2)) in our subjects and 100% (strenuous) of IAT, corresponding to about 69% peak VO(2). Blood samples were taken after 30 min rest and immediately after exercise. CD62P expression and differentiated platelet-leukocyte conjugates (CD45, CD14, CD41) as well as microparticles and platelet-platelet aggregates were detected flow cytometrically with and without TRAP-6-stimulation. RESULTS: CD62P expression and the number of aggregates were increased (P< or =0.05) after exercise in the TRAP-stimulation experiment independent of exercise intensity. The number of platelet-granulocyte (rest 5.7+/-1.8 to post 8.1+/-1.7 (80%) vs. 6.2+/-1.9 to 10.3+/-2.0 (100%)), platelet-monocyte (5.3+/-3.6 to 8.5+/-3.7 (80%) vs. 7.4+/-3.5 to 11.7+/-4.8 (100%)), and platelet-lymphocyte conjugates (4.4+/-1.2 to 6.4+/-1.3 (80%) vs. 4.6+/-1.7 to 7.8+/-1.8% positive cells (100%)) were also higher after both exercises but increased significantly weaker (P< or =0.05) after moderate exercise. These results were confirmed by the TRAP-stimulation experiment. CONCLUSION: Although moderate exercise led to an increase in platelet reactivity and platelet-leukocyte conjugate formation the changes in conjugate formation were significantly weaker compared to strenuous exercise. Therefore it is recommended that submaximal endurance performance should be individually developed in order for everyone to be able to carry out normal daily activities and also to exercise well below the IAT.