Return to work after spinal cord injury: the potential contribution of physical fitness.
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The history, physical characteristics and fitness status of 60 persons who had sustained a spinal cord injury at least 3 years previously were considered in relation to current occupation. All subjects had completed their education, 39 being gainfully employed and 21 unemployed. The general characteristics of the sample, mainly beneficiaries of the Quebec Automobile Insurance Plan, were typical of spinal cord injured individuals in North America. The working group had a significantly higher current level of education than those who were unemployed (p less than .01). In terms of physical fitness, the workers were lighter, with a lower body mass index and a higher aerobic power (p less than .05). Isokinetic testing suggested a trend toward a higher peak torque in the workers. The total work performed (Nm.kg-1) during an isokinetic endurance test (25 biphasic contraction at 180 degrees.sec-1) was significantly higher in the workers, suggesting that such muscular endurance might be even more useful than greater peak isokinetic strength during vocational activities. However, the likelihood of employment was unrelated to habitual patterns of either aerobic exercise or overall physical activity. No significant differences of physical fitness or physical activity habits were found between workers holding sedentary versus physically demanding jobs. The results verified the positive relationship between physical fitness (body composition, aerobic power, muscular endurance) and the gainful employment of paraplegics, but failed to show any significant relationship between physical fitness and the acceptance of physically demanding work by such individuals. (+info)
Evaluation of physiological standard pressures of the forearm flexor muscles during sport specific ergometry in sport climbers.
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BACKGROUND: Chronic exertional compartment syndromes (CECS) are well known in sports medicine. Most commonly affected is the tibialis anterior muscle compartment in runners and walkers. Only a few cases of CECS of the forearm flexor muscles have been reported. OBJECTIVES: To determine pressure levels inside the deep flexor compartment of the forearms during a sport specific stress test. METHOD: Ten healthy, high level climbers were enrolled in a prospective study. All underwent climbing specific ergometry, using a rotating climbing wall (step test, total climbing time 9-15 minutes). Pressure was measured using a slit catheter placed in the deep flexor compartment of the forearm. Pressure, blood lactate, and heart rate were recorded every three minutes and during recovery. RESULTS: In all the subjects, physical exhaustion of the forearms defined the end point of the climbing ergometry. Blood lactate increased with physical stress, reaching a mean of 3.48 mmol/l. Compartment pressure was related to physical stress, exceeding 30 mm Hg in only three subjects. A critical pressure of more than 40 mm Hg was never observed. After the test, the pressure decreased to normal levels within three minutes in seven subjects. The three with higher pressure levels (>30 mm Hg) required a longer time to recover. CONCLUSIONS: For further clinical and therapeutic consequences, an algorithm was derived. Basic pressure below 15 mm Hg and stress pressure below 30 mm Hg as well as pressures during the 15 minute recovery period below 15 mm Hg are physiological. Pressures of 15-30 mm Hg during recovery suggest high risk of CECS, and pressures above 30 mm Hg confirm CECS. (+info)
On issues of confidence in determining the time constant for oxygen uptake kinetics.
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BACKGROUND: TauVO(2 )at the onset of constant work rate (CWR) exercise is a variable of aerobic fitness that shortens with physical training and lengthens with cardiopulmonary disease. Determination of tauVO(2) with sufficiently high confidence has typically required multiple exercise transitions limiting its clinical application. OBJECTIVES: To design a protocol to determine tauVO(2) reliably but simply. METHODS: On each of three days, five healthy men performed two CWR tests on a cycle ergometer below the metabolic threshold (VO(2)theta) for blood lactate accumulation as determined by gas exchange measurements followed by an incremental work rate (IWR) test. TauVO(2) was determined (a) from the on-transit (on-tauVO(2)) and off-transit (off-tauVO(2)) of six CWR tests both individually and superimposed, using non-linear regression with a monoexponential model, and (b) by geometric analysis of the IWR tests (ramp-tauVO(2)). RESULTS: Group means (SD) were: VO(2)max 3.84 (0.44) litres/min, VO(2)theta 1.88 (0.23) litres/min, steady state exercise VO(2) 1.67 (0.07) litres/min, on-tauVO(2) 38.0 (5.3) seconds, off-tauVO(2) 39.0 (4.3) seconds, and ramp-tauVO(2) 60.8 (15.4) seconds. On-tauVO(2) correlated with off-tauVO(2) (r = 0.87), VO(2)max (r = -0.73), and VO(2)theta (r = 0.89). The pooled mean tauVO(2) from six superimposed tests agreed with the arithmetic grand mean of the six tests. CONCLUSIONS: The average of on-tauVO(2) and off-tauVO(2) fell within the 95% confidence interval of the pooled mean by the second test. Ramp-tauVO(2) was longer and less reproducible. These findings support the use of both on- and off-transit data for the determination of tauVO(2), an approach that reduces the number of transitions necessary for accurate determination of tauVO(2), potentially enhancing its clinical application. (+info)
Which laboratory variable is related with time trial performance time in the Tour de France?
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OBJECTIVE: To investigate the relationship between several physiological variables that can be easily obtained during cycle ergometer gradual testing (for example, peak power output (W(peak)), Vo(2max), or ventilatory threshold (VT)) and actual (>50 km) time trials (TT) time performance during the Tour de France. METHODS: We collected data in professional cyclists from the first TT of the 1998 Tour de France (TT1, 58 km distance; n = 6 cyclists) and the first (TT2, 56.5 km; n = 5) and second TT of the 1999 Tour de France (TT3, 57 km; n = 5). RESULTS: A negative relationship was found between power output (W) at VT (VT(Watt)) and TT final time (s) in TT1 (r = -0.864; p = 0.026; standard error of estimate (SEE) of 73 s; and 95% confidence limits (95% CL) -0.98; -0.18), TT2 (r = -0.77; p = 0.27; SEE of 139 s; and 95% CL -0.98; 0.35), and TT3 (r = -0.923; p = 0.025; SEE of 94 s; and 95% CL -1.00; -0.22). CONCLUSIONS: Actual performance in long TT during the Tour de France (>50 km distance, performed after at least 1-2 weeks of continuous competition), in which some cumulative fatigue inevitably occurs, is related, at least in part, to the power output that elicits the VT. No other routine physiological variable (for example, Vo(2max) or W(peak)) is related to performance in this type of event. (+info)
The biomechanics of wheelchair propulsion in individuals with and without upper-limb impairment.
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We used an instrumented wheelchair ergometer and 3D motion analysis system to collect joint kinematic and temporal data, as well as hand rim and joint kinetics, in 47 manual wheelchair users (MWCUs) (15 with upper-limb impairment and 32 without upper-limb impairment). The group with upper-limb impairment propelled with a higher stroke frequency and reduced hand-rim contact time, and smaller peak joint angles and joint excursion of the wrist, elbow, and shoulder during the contact phase. They also propelled with a reduced power output and reduced hand-rim propulsive and resultant forces, moments, and joint compressive forces. We concluded that these kinematic and kinetic strategies might be a mechanism for allowing MWCUs with upper-limb impairment to remain independent. Additionally, the reduced joint excursion and reduced magnitude of forces may protect them from the development of secondary upper-limb pathologies. (+info)
The effects of rear-wheel camber on the mechanical parameters produced during the wheelchair sprinting of handibasketball athletes.
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The wheel camber of a wheelchair is a significant parameter that must be taken into account in the search for optimal regulation of a wheelchair. This study examined the effects of different rear-wheel camber (9 degrees , 12 degrees and 15 degrees )-today used mainly in the handibasket championship-on the various kinetic and kinematic parameters of the propulsion cycle. Eight males, all players in the French handibasket championship, were asked to participate in this study. They performed three 8 s maximal sprints as measured by a wheelchair ergometer, 9 degrees , 12 degrees , and 15 degrees of rear-wheel camber. The results of our study show that residual torque increases in proportion to the increase in wheel camber. This could explain other study results, which show a decrease in mean velocity and an increase in both power output and time of the propelling phase, in relation to the wheel camber. These results should provide the information necessary for optimal wheelchair regulation. (+info)
Comparison of different exercise tests in assessing outcomes of pulmonary rehabilitation.
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INTRODUCTION: Common modalities of clinical exercise testing for outcome measurement after pulmonary rehabilitation (PR) include walk tests, progressive cycle ergometry, and cycle endurance testing. We hypothesized that patients' responses to PR, as measured by those 3 tests, are differentially correlated, and we designed a study to investigate the tests' capacity to detect changes after PR. METHODS: We prospectively tested 37 male patients with stable chronic obstructive pulmonary disease who completed a comprehensive 6-week PR program that included supervised exercise training that emphasized steady-state lower-limb aerobic exercise. Before and after the PR program the patients underwent 6-minute walk test, progressive cycle ergometry, and cycle endurance testing (at 80% of the peak work rate achieved during progressive cycle ergometry). The exercise performance indices of interest were the peak oxygen uptake (VO2max) and maximum work-rate (Wmax) during progressive cycle ergometry, the cycling endurance time, and the 6-minute walk distance (6MWD). RESULTS: After PR there were statistically significant improvements in 6MWD (16%, p <0.001), VO2max (53%, p=0.004), Wmax (30%, p=0.001), and cycling endurance time (144%, p <0.001). The changes in VO2max and Wmax were significantly correlated (r=0.362, p=0.027), as were the changes in endurance time and Wmax (r=0.406, p=0.013). There was no significant correlation between changes in any other exercise index. CONCLUSIONS: Among the frequently used exercise tests in PR, the most responsive index is the endurance time. The correlation between the post-PR changes in the various exercise indices is poor. (+info)
Ground reaction forces associated with an effective elementary school based jumping intervention.
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BACKGROUND: Mechanical loading during childhood plays a critical role in normal growth and development of the skeleton. Ground reaction forces (GRFs) may provide a surrogate measure for the strain experienced by bone on landing and at take off. However, there appear to be no paediatric studies that assess GRFs across a variety of loading activities. OBJECTIVES: To measure biomechanical variables in commonly performed childhood activities used in an elementary physical education intervention study which augmented bone health in boys and girls. METHODS: Maximal GFR, maximal rates of force, and time to maximum force were measured for 12 different jumping activities on a force platform. The jumps measured were drop jumps from 10, 30, and 50 cm, all followed by a plyometric jump, submaximal and maximal jumping jacks, alternating feet jump, counter movement jumps, and side to side jumps over 10 and 20 cm foam barriers. The subjects were 70 children (36 boys and 34 girls), 8.3-11.7 years old. RESULTS: Subjects ranged in height from 128.4 to 172.6 cm and had a mass of 25.0-57.0 kg. Mean (SD) for vertical jump was 24.2 (5.5) cm and 135.2 (16.6) cm for standing long jump. The children engaged in loaded physical activity 5.7 (5.3) hours a week, on average. The highest mean maximal GRFs, normalised for body weight (BW), were generated from the plyometric portion of the drop jumps and the counter movement jump (about 5 times BW) compared with 3.5 times BW for jumping jacks. Similarly, the highest rates of change in force were 514 times BW/s for the drop jump from 10 cm and 493 times BW/s for the counter movement jump. CONCLUSIONS: Simple jumps requiring minimal equipment produce GRFs of 3.5-5 times BW and rates of force of around 500 times BW/s. As children appear to attenuate higher impact forces when jumping from increased heights, it cannot be assumed that merely increasing the height of the jump will necessarily "progress" the exercise intervention. (+info)