The purpose of this study was to compare quadriplegic and able-bodied men on selected cardiovascular and metabolic responses to arm-crank ergometry at the same rate of oxygen consumption (V̇O2). Subjects included 11 untrained, spinal cord-injured, C5–C7 complete quadriplegic men and 11 untrained, able-bodied men of similar age (27 years), height (177 cm), and mass (65 kg). Measurement techniques included open-circuit spirometry, impedance cardiography, and electrocardiography. Compared with the able-bodied group, at the V̇O2 of 0.5 L/min, the quadriplegics displayed a significantly higher mean heart rate and arteriovenous O2 difference, lower stroke volume and cardiac output, and similar myocardial contractility. These results suggest that quadriplegic men achieve an exercise-induced V̇O2 of 0.5 L/min through different central cardiovascular adjustments than do able-bodied men. Quadriplegics deliver less O2 from the heart toward the tissues but extract more O2 from the blood. Tachycardia may contribute to low cardiac preload and low stroke volume, while paradoxically tending to compensate for low stroke volume by minimizing reduction of cardiac output.
Stephen F. Figoni, Richard A. Boileau, Benjamin H. Massey and Joseph R. Larsen
Stamatis Agiovlasitis, Kenneth H. Pitetti, Myriam Guerra and Bo Fernhall
This study examined whether 20-m shuttle-run performance, sex, body mass index (BMI), age, height, and weight are associated with peak oxygen uptake (VO2peak) in youth with Down syndrome (DS; n = 53; 25 women, age 8–20 years) and whether these variables can be used to develop an equation to predict VO2peak. BMI, 20-m shuttle-run performance, and sex were significantly associated with VO2peak in youth with DS, whereas age, height, and weight were not. A regression model included only shuttle-run performance as a significant predictor of VO2peak; however, the developed prediction equation had low individual predictability. Therefore, 20-m shuttle-run performance alone does not provide valid prediction of VO2peak in youth with DS. Sex, BMI, age, height, and weight do not improve the prediction of VO2peak.
Mário A.M. Simim, Marco Túlio de Mello, Bruno V.C. Silva, Dayane F. Rodrigues, João Paulo P. Rosa, Bruno Pena Couto and Andressa da Silva
3 ± 2 hr/week Two visits to laboratory (first = incremental test and VO 2 peak test; second = 20-min exercise tests—50% and 70% of VO 2peak ) TRA VO 2 %VO 2peak HR %HR peak [Lac] RPE HR monitors Lactate Pro handbike Borg scale 6–20 PPO Handbike Barfield et al. ( 2010 ) 9 WR SCI (C6–C7) 12 ± 7 9 ± 6
Stamatis Agiovlasitis, Jeffrey A. McCubbin, Joonkoo Yun, Michael J. Pavol and Jeffrey J. Widrick
This study examined whether the net rate of oxygen uptake (VO2net) and the net oxygen uptake per kilometer (VO2net/km) are affected during walking in adults with Down syndrome (DS) and whether their preferred walking speed (PWS) minimizes the VO2net/km. Respiratory gases were collected as 14 adults with DS and 15 adults without DS completed a series of treadmill walking trials. PWS was measured over 15 meters in a hallway. The VO2net and the VO2net/km were higher in adults with DS than adults without DS. The overground PWS normalized for leg length was the same for both groups and did not appear to minimize the VO2net/km. Thus, adults with DS are less economical during walking than adults without DS. The overground PWS does not minimize the metabolic cost during treadmill walking.
Gregory B. Dwyer and Anthony D. Mahon
Little is known about the responses to graded exercise in athletes with cerebral palsy (CP). This study compared the ventilatory threshold (VT) and peak VO2 among athletes with CP during treadmill and cycle ergometry exercise. Six (4 men, 2 women) track athletes with CP volunteered to participate in the study. Graded exercise tests on a treadmill and cycle ergometer were performed on separate days to assess VT and peak VO2. Paired t tests were used to compare the two exercise modes. The VT, expressed as a percentage of peak VO2, was significantly higher on the cycle ergometer than on the treadmill. The absolute VO2 at the VT was similar during both testing modes, and peak VO2 was significantly higher on the treadmill than on the cycle ergometer. Similar to responses seen in able-bodied individuals, the VO2 at VT was similar during both modes of exercise, while the peak VO2 was 10% lower on the cycle than on the treadmill. Cycle ergometer peak VO2 in these athletes was higher than previous reports of individuals with CP for the cycle ergometer.
Thomas J. O’Connor, Rick N. Robertson and Rory A. Cooper
Three-dimensional kinematic variables and their relationship to the physiology of racing wheelchair propulsion were studied. Six male wheelchair athletes performed two trials (medium and maximum speed) of 3 min each. VO2, VO2/kg, VE, and HR were measured. Results showed that at medium speed, wrist velocity on hand contact was significantly correlated with VO2/kg. At maximum speed, elbow velocity during preparatory phase was significantly correlated with VO2. Stepwise regression showed wrist trajectory angle and elbow velocity during preparatory phase were significantly correlated with VO2/kg. Results indicate that kinematic variables recorded prior to and on hand contact with the pushrim are significant variables in developing a more efficient racing wheelchair propulsion technique. Results of this study indicate a need to educate coaches of wheelchair track athletes concerning the best racing wheelchair propulsion technique.
M. Kathleen Ellis and Lynn A. Darby
This study compared balance and peak oxygen consumption (peak VO2) among hearing, congenital nonhearing, and acquired nonhearing female intercollegiate athletes. Twenty-seven subjects completed two measures of peak VO2 and two measures of balance (static and dynamic). Two pieces of exercise equipment requiring different levels of balance were used: the bicycle ergometer (minimal balance) and the bench-step (maximal balance). Significant differences were found for dynamic balance and for peak VO2 for all subject groups. The significant difference remained among the groups for peak VO2 using the bicycle ergometer when dynamic balance was used as a covariate. There was no significant difference for peak VO2 dependent on type of test when dynamic balance was controlled. The results indicated that dynamic balance affected peak VO2 performance on the bench-step, but not on the bicycle ergometer. These findings suggest that if dynamic balance is required for an assessment of peak VO2, balance should be tested in nonhearing populations.
Yagesh N. Bhambhani, Robert S. Burnham, Gary D. Wheeler, Peter Eriksson, Leona J. Holland and Robert D. Steadward
In this study we compared the ventilatory threshold (VT) between 8 untrained and 8 endurance-trained males with quadriplegia during simulated wheelchair exercise. Each subject completed an incremental velocity test in his personal wheelchair mounted on a customized roller system designed to provide velocity and distance feedback. VT was identified by two trained evaluators using established respiratory gas exchange criteria. A significant interevaluator reliability coefficient of .90 (p < .01) was observed for the detection of VT. Relative oxygen uptake (V̇O2, ml · kg-1 · min-1) at VT and peak V̇O2 were significantly (p < .05) higher in the endurance-trained compared to untrained subjects. However, no significant difference (p > .05) was observed between the two groups when VT was expressed as a percentage of peak V̇O2. Significant correlations of .86 and .81 (p < .01) were observed between VT and peak V̇O2 in the untrained and trained groups, respectively. It was concluded that endurance training improves both VT and peak V̇O2 during wheelchair exercise in male subjects with quadriplegia but does not improve VT when it is expressed relative to peak V̇O2.
Ian G. Campbell, Clyde Williams and Henryk K.A. Lakomy
The purpose was to examine selected physiological responses of endurance-trained male wheelchair athletes in different Paralympic racing classes (T2, n = 3; T3, n = 8; T4, n = 7) during a 10-km treadmill time trial (TM:10-km). Peak oxygen uptake (V̇O2 peak) was determined, and a TM:10-km was completed on a motorized treadmill. From this, % V̇O2peak utilized and the relationship between V̇O2peak and TM:10-km were established. During the TM:10-km, the following dependent variables were examined: propulsion speed, oxygen uptake, respiratory exchange ratio, and heart rate. The results showed athletes utilize a high % V̇O2peak (78.4 –13.6%) during the TM:10-km. There was a moderate correlation (r = -.57, p < .01) between VO2peak and TM:10-km. No physiological differences were found between the paraplegic racing classes (T3, T4), which suggests that there is some justification in amalgamating these racing classes for endurance events.
George T. Hardison Jr., Richard G. Israel and Grant W. Somes
The purpose of this study was to identify the most desirable cranking rate to be used by paraplegic individuals during submaximal arm training programs. Eleven healthy paraplegic males (M age = 28.8 years) with lesion levels ranging from T4 to T12 served as subjects. Arm exercise loads for the four submaximal cranking rates studied (50, 60, 70, and 80 rpm) were set to elicit 60% of peak V̇O2. Duration of the submaximal tests was 15 min. V̇E, V̇O2, RER, HR, and differentiated RPE were recorded each minute throughout the 15-min test. A randomized block ANOVA and Duncan’s post hoc analysis indicated that 80 rpm produced significantly higher (p <.05) values for HR, absolute V̇O2, V̇E, V̇CO2, and V̇E/V̇O2 than any other rates. Cranking at 70 rpm resulted in significantly higher (p <.05) values for O2 pulse, while relative V̇O2 was significantly higher (p <05) at 70 rpm than at all other rates except 80 rpm. RPE was significantly higher (p <.05) at 50 rpm than at 60 or 70 rpm, with no difference between 50 and 80 or 60, 70, and 80. The authors concluded that 70 rpm was the most appropriate cranking rate for paraplegic males to use during arm training programs.