Donald Anthony Schneider

The simplified V-slope method of detecting the gas exchange threshold.

A simplified V-slope method was used to visually determine the first point of departure from linearity of carbon dioxide output (VCO2) plotted against oxygen uptake (VO2). The point at which VCO2 departed from a line with a slope equal to 1.00 was visually selected as the gas exchange threshold during incremental exercise. The simplified method of threshold detection was compared with a computerized V-slope method. Both methods were used to determine the gas exchange threshold during incremental cycling (10 W.min-1) in 17 untrained female subjects. The thresholds occurred at 41.1% and 45.1% of VO2max using the computerized and simplified V-slope methods, respectively. The correlation between the oxygen uptake measured at the threshold using the two methods was 0.95. Power output, VO2, and heart rate values determined at the gas exchange threshold using the simplified V-slope method were significantly higher than the corresponding values obtained using the computerized V-slope method. The simplified V-slope method consistently placed the gas exchange threshold at the work rate that was about 10 W above the power output determined by the computerized method. Although the two methods were highly correlated, the simplified V-slope method tended to overestimate threshold values determined from a computerized gas exchange method.

Continuous and intermittent exercise responses in individuals with chronic obstructive pulmonary disease

Background: While the acute physiological responses to continuous exercise have been well documented in individuals with chronic obstructive pulmonary disease (COPD), no previous study has examined the response to intermittent exercise in these patients. Methods: We examined the physiological responses of 10 individuals with moderate COPD (forced expiratory volume in 1 second 52 (15)% predicted) who performed both an intermittent (1 min exercise and rest intervals) and a continuous cycle ergometer test on separate days. Both intermittent and continuous exercise tests were performed at the same power output, calculated as 70% of the peak power attained during an incremental exercise test. Results: Intermittent exercise was associated with significantly lower values for oxygen uptake, carbon dioxide output, expired ventilation, heart rate, plasma lactate concentration, and ratings of breathlessness than continuous exercise. Subjects were able to complete a significantly greater total amount of work during intermittent exercise (71 (32) kJ) than during continuous exercise (31 (24) kJ). The degree of dynamic lung hyperinflation (change in end expiratory lung volume) was significantly lower during intermittent exercise (0.23 (0.07) l) than in continuous exercise (0.52 (0.13) l). Conclusions: The greater amount of work performed and lower measured physiological responses achieved with intermittent exercise may allow for greater peripheral training adaptations in individuals with more limited lung function. The results suggest that intermittent exercise may be superior to continuous exercise as a mode of training for patients with COPD.

Plasma catecholamine and blood lactate responses to incremental arm and leg exercise

PURPOSE AND METHODS The present study was conducted to examine the pattern of plasma catecholamine and blood lactate responses to incremental arm and leg exercise. Seven untrained male subjects performed two incremental exercise tests on separate days in random order. One test consisted of 1-arm cranking (5W x 2 min(-1)), whereas the other exercise test was 2-leg cycling (20-25W x 2 min(-1)). Blood samples were obtained from the nonexercising arm during 1-arm cranking and from the same arm and vein during 2-leg cycling. Thresholds for blood lactate (T(La)), epinephrine (T(Epi)) and norepinephrine (T(NE)) were determined for each subject under both exercise conditions and defined as breakpoints when plotted as a function of power output. RESULTS When the two modes of exercise were compared, T(La), T(Epi), and T(NE) were all significantly lower for 1-arm cranking than for 2-leg cycling (P < 0.01). During 1-arm cranking, T(La) (0.96 +/- 0.10 L x min(-1)), T(Epi) (1.02 +/- 0.07 L x min(-1)), and T(NE) (1.07 +/- 0.09 L x min(-1)) occurred simultaneously. During 2-leg cycling, T(La) (1.77 +/- 0.20 L x min(-1)), T(Epi) (1.74 +/- 0.17 L x min(-1)), and T(NE) (1.98 +/- 0.17 L x min(-1)) occurred at similar levels of VO2 and were not significantly different. The correlation observed between the VO2 measured at the T(La) and T(Epi) was 0.917 for arm and 0.929 for leg exercise (P < 0.001). The epinephrine concentration ([Epi]) obtained at the T(La) was not significantly different for arm (0.144 ng x mL(-1)) and leg (0.152 ng x mL(-1)) exercise. CONCLUSIONS The breakpoint in plasma [Epi] shifted in an identical manner and occurred simultaneously with that of T(La) regardless of the mode of exercise (arm or leg). The Epi concentrations observed at the T(La) agree with those previously reported to produce a rise in blood lactate during Epi infusion at rest. These results support the hypothesis that a rise in plasma [Epi] may contribute to the breakpoint in blood lactate that occurs during incremental exercise.

Reliability of MAOD measured at 110% and 120% of peak oxygen uptake for cycling.

PURPOSE The purpose of this study was to examine the test-retest reliability of maximal accumulated oxygen deficit (MAOD) measured at 110% and 120% of peak oxygen uptake (VO2) for cycling in seven untrained male and seven untrained female subjects. METHODS After one familiarization trial, all subjects performed two MAOD tests at a power output corresponding to 110% and two tests at 120% of VO2peak in random order. MAOD was calculated for each subject as the difference between O2 demand during exercise and the measured VO2. RESULTS The mean (+/-SEM) time to exhaustion for the group was not significantly different between trial 1 (226 +/- 13 s) and trial 2 (223 +/- 14 s) of the 110% test. Likewise, the difference in the time to exhaustion between trial 1 (158 +/- 11 s) and trial 2 (159 +/- 10 s) was not significant for the 120% test. The intraclass correlation coefficients for the time to exhaustion were 0.95 for the 110% test and 0.98 for the 120% test. The mean MAOD value obtained in trial 1 (2.62 +/- 0.17 L) was not significantly different from the mean value obtained in trial 2 (2.54 +/- 0.19 L) for the 110% test. Additionally, the mean values for the two trials did not differ significantly for MAOD (2.64 +/- 0.21 L for trial 1 and 2.63 +/- 0.19 L for trial 2) in the 120% test. The intraclass correlation coefficients for MAOD were 0.95 for the 110% test and 0.97 for the 120% test. All intraclass correlation coefficients were significant at P < 0.001. CONCLUSIONS When conducted under standardized conditions, the determination of MAOD for cycling was highly repeatable at both 110% and 120% of VO2peak in untrained male and female subjects.

Maximal accumulated oxygen deficit expressed relative to the active muscle mass for cycling in untrained male and female subjects.

Abstract The purpose of the present study was to determine if gender differences exist in the maximal accumulated oxygen deficit (MAOD) or in the blood lactate (Lac−) and catecholamine responses to the MAOD test (120% peak oxygen uptake to exhaustion). The MAOD for cycling was measured in ten untrained male and ten untrained female subjects using the method described by Medbø et al. (Anaerobic capacity determined by maximal accumulated oxygen deficit. J Appl Physiol 64: 50–60, 1988). Blood Lac− and catecholamine concentrations were measured at rest, exhaustion and for 30 min following the MAOD test. Dual-energy X-ray absorptiometry was used to measure lean body mass (LBM) and to estimate the active muscle mass (AMM) for cycling. Males achieved a significantly higher MAOD than females following correction for AMM [126.3 (5.6) versus 108.3 (6.1) ml · kg AMM−1, P=0.04]. The peak blood lactate concentration ([Lac−]) in males [13.6 (0.9) mmol · l−1] was significantly higher than in females [10.0 (1.0) mmol · l−1]. Males obtained a 68% higher peak epinephrine concentration ([Epi]) than females, but the difference was not significant [1268 (188) pg · ml−1 versus 755 (179) pg · ml−1, P=0.066]. However, plasma [Epi] was significantly higher for males than females at 1 min [824 (116) versus 489 (116) pg · ml−1, P=0.036] and 3 min [330 (52) versus 179 (42) pg · ml−1, P=0.039] into the recovery period. No gender-dependent differences in the norepinephrine concentration were observed at any time. Peak [Lac−] was significantly correlated with MAOD (ml · kg AMM−1) in females (r=0.75), but not in males (r=0.09). The peak plasma [Epi] was not significantly correlated with MAOD (ml · kg AMM−1) or peak [Lac−] in either group. These findings suggest that there are gender-dependent differences in MAOD even when expressed relative to the AMM for cycling. The higher blood [Lac−] in males compared to females obtained after supramaximal exercise was not caused by enhanced secretion of Epi. The greater MAOD in untrained males was not caused by a greater ability to produce Lac− or by enhanced secretion of Epi.

Muscle glycogen reduction in man: relationship between surface EMG activity and oxygen uptake kinetics during heavy exercise

The purpose of this study was to determine whether muscle glycogen reduction prior to exercise would alter muscle fibre recruitment pattern and change either on‐transient O2 uptake ( ) kinetics or the slow component. Eight recreational cyclists ( , 55.6 ± 1.3 ml kg −1 min−1) were studied during 8 min of heavy constant‐load cycling performed under control conditions (CON) and under conditions of reduced type I muscle glycogen content (GR). was measured breath‐by‐breath for the determination of kinetics using a double‐exponential model with independent time delays. was higher in the GR trial compared to the CON trial as a result of augmented phase I and II amplitudes, with no difference between trials in the phase II time constant or the magnitude of the slow component. The mean power frequency (MPF) of electromyography activity for the vastus medialis increased over time during both trials, with a greater rate of increase observed in the GR trial compared to the CON trial. The results suggest that the recruitment of additional type II motor units contributed to the slow component in both trials. An increase in fat metabolism and augmented type II motor unit recruitment contributed to the higher in the GR trial. However, the greater rate of increase in the recruitment of type II motor units in the GR trial may not have been of sufficient magnitude to further elevate the slow component when was already high and approaching .

V˙O2peak and the gas-exchange anaerobic threshold during incremental arm cranking in able-bodied and paraplegic men

Abstract Resting energy expenditure, peak oxygen uptake (V˙O2peak) and the gas-exchange anaerobic threshold (Than) were measured during incremental arm cranking (15 W · min−1) in six able-bodied (AB) and six paraplegic (P) subjects. Only male subjects with traumatic spinal cord injuries in the area of the 10–12th thoracic segment were included in the P group. All AB and P subjects were physically active. Mean (SE) values for age and body mass were 28 (2) years and 78.9 (3.9) kg for the AB group and 32 (4) years and 70.8 (7.9) kg for the P group (P > 0.05). Resting energy expenditure values were not found to be significantly different between AB [5.8 (0.2) kJ · min−1] and P [5.1 (0.3) kJ · min−1] subjects. Mean V˙O2peak values were 29.3 (2.4) ml · kg−1 · min−1 and 29.6 (2.2) ml · kg−1 · min−1 for the AB and P groups, respectively (P > 0.05). Absolute oxygen uptake values measured at two gas-exchange anaerobic threshold (Than) were not significantly different between the two groups. However, the Than occurred at a significantly higher percentage of V˙O2peak in the P [58.9 (1.7)%] group than in the AB [50.0 (2.8)%] group (P < 0.05). Moreover, respiratory exchange ratio (R) values obtained at the Than and at 15, 45, 60, 75 and 90 W of incremental exercise were significantly lower in the P group than in the AB group. Heart rates were significantly elevated at every submaximal work stage (15–120 W) in the P group compared to the AB group (P < 0.05). These findings suggest that chronic daily wheelchair activity produces local adaptations in the functional upper-body musculature, which reduce glycogenolysis and increase the rate of lipid utilization (lower R) during arm exercise. These local adaptations may be in part responsible for the significantly higher Than observed for arm exercise in P subjects, even though V˙O2peak values were essentially the same for both groups.

Verbal numerical scales are as reliable and sensitive as visual analog scales for rating dyspnea in young and older subjects

This study compared the use of a simple verbal 0-10 numerical rating scale (verbal NRS) and a visual analog scale (VAS) for the rating of dyspnea during exercise in a group of young and older subjects. Twelve younger (32+/-9 yr) and 12 older (71+/-7 yr) subjects used either the verbal NRS or the VAS in a randomised fashion to rate dyspnea during 60 s of uphill treadmill walking (range 5.6-8.8 km h(-1)) performed at either a low (17% grade) or high workload (26% grade) and then during recovery. Rating scales were evaluated twice on separate days (day 1 and day 2) at each workload. While the verbal NRS scores proved to be reliable throughout exercise and recovery, VAS scores were significantly (p<0.05) lower on day 2 during the low workload test (younger group) and the high workload test (older group). Verbal NRS ratings were consistently greater than VAS ratings at both workloads (p<0.001) for both young and older groups. The intra-class correlation coefficients for rating peak dyspnea using either the VAS or verbal NRS were consistently lower for the older subjects (range: r=0.54-0.67) than the younger subjects (range: r=0.70-0.86). Overall, subjects preferred the verbal NRS to the VAS. These results suggest that the verbal NRS compares favourably with the VAS for rating dyspnea during exercise without mask or mouthpiece. However, when rating peak dyspnea both scales appear less reliable when used by the older compared to young subjects.

Oxygen uptake kinetics during severe exercise: a comparison between young and older men

This study examined the relationship between the slow component of oxygen uptake (VO2) kinetics and muscle electromyography (EMG) during severe exercise in nine young (21.7+/-0.9 yr) and nine older (71.6+/-0.8 yr) men. Oxygen uptake (VO2) and surface EMG activity of the left vastus lateralis muscle were measured during a 7-min square-wave bout of severe exercise on a cycle ergometer. The absolute amplitude of the VO2 slow component was greater and occurred approximately 60 s earlier in the young compared to older subjects. However, the rate of increase in the slow component, expressed as a percentage of the total VO2 response per unit time, was not different between young and older subjects (young: 4.8+/-0.5%.min(-1); older: 4.9+/-0.6%.min(-1)). The mean power frequency (MPF) of the EMG increased significantly during the slow component phase of exercise by 6.4+/-1.0% in the young and by 5.4+/-0.7% in the older group and this rise was not significantly different between the two groups. These results indicate that normal ageing may not alter the VO2 slow component (measured as the rate of increase in VO2) and that this finding may be related to similar muscle fibre recruitment patterns in the two groups during severe-intensity exercise.

Breathing He-O2 attenuates the slow component of O2 uptake kinetics during exercise performed above the respiratory compensation threshold.

The contribution of respiratory muscle O2 uptake to the development of the slow component of O2 uptake kinetics is unclear. The aim of the present study was to examine the impact of respiratory muscle unloading (via breathing, a He–O2 mixture) on the amplitude of during exercise performed below (B‐RCT) and above the respiratory compensation threshold (A‐RCT). We hypothesized that breathing He–O2 would reduce the amplitude of the by a greater amount during exercise performed A‐RCT than B‐RCT. Eight healthy male recreational cyclists performed constant‐load cycling in four sets of conditions: (1) B‐RCT breathing normal air; (2) B‐RCT breathing He–O2; (3) A‐RCT breathing normal air; and (4) A‐RCT breathing He–O2. Breathing He–O2 did not significantly attenuate the during exercise performed B‐RCT (–3 ± 14%, P > 0.05). However, breathing He–O2 significantly reduced the during exercise A‐RCT (–45 ± 6%, P < 0.05). The attenuated while breathing He–O2 is likely to reflect a decreased . Minute ventilation was not different between normal air and He–O2 breathing trials either B‐RCT or A‐RCT. However, operating lung volume was significantly lower when breathing He–O2 during exercise performed A‐RCT (–12 ± 3%, P < 0.05). These findings suggest that comprises a greater proportion of the when exercise is performed A‐RCT compared with B‐RCT. Therefore, the impact of breathing He–O2 was more pronounced during exercise A‐RCT. Furthermore, changes in operating lung volume and the work of breathing appear to play an important role in the development of the .