Ventilatory responses during varied stride and pedal frequencies

V[Combining Dot Above]O2peak Comparison of a Treadmill Vs. Cycling Protocol in Elite Teenage Competitive Runners, Cyclists, and Swimmers

ABSTRACT

Marko, D, Bahenský, P, Snarr, RL, and Malátová, R. V[Combining Dot Above]O2peak Comparison of a treadmill vs. cycling protocol in elite teenage competitive runners, cyclists, and swimmers. J Strength Cond Res XX(X): 000-000, 2021-The purpose of this study was to compare the cardiorespiratory and metabolic responses of a maximal graded exercise test (GXT) on a treadmill and cycle ergometer in elite-level, youth competitive athletes. Thirty-one athletes (11 distance runners, 11 mountain-bike cyclists, and 9 long-distance swimmers) were randomly selected to complete either a running or cycling GXT on the first day, followed by the alternative 72 hours apart. The initial work rate for each GXT was set at 50% of the individuals' previously established V[Combining Dot Above]O2peak to elicit fatigue within 8-12 minutes. For the treadmill protocol, speed was increased by 1 km·h-1 each minute, with a constant 5% grade, until volitional fatigue. Cycle ergometer work rate was increased by 30 W every minute until volitional fatigue or the inability to maintain proper cadence (i.e., 100 ± 5 rev·min-1). Throughout both testing sessions, V[Combining Dot Above]O2peak, heart rate [HR] peak, breathing frequency (BF), tidal volume (VT), and minute ventilation (VE) were assessed and used to compare within-sport differences. Runners displayed a higher V[Combining Dot Above]O2peak (∼7%; d = 0.92), HRpeak (4%; d = 0.77), VE (6%; d = 0.66), and BF (12%; d = 0.62) on the treadmill vs. cycle. However, the cycling group demonstrated a greater V[Combining Dot Above]O2peak (∼8%; d = 0.92), VT (∼14%; d = 0.99), and VE (∼9%; d = 0.78) on the cycle, despite no change in HRpeak. For swimmers, the treadmill GXT elicited higher values in V[Combining Dot Above]O2peak (∼5%; d = 0.75), BF (∼11.5%; d = 0.78), and HRpeak (3%; d = 0.69). Collectively, these findings indicate that exercise mode may greatly affect physiological outcome variables and should be considered before exercise prescription and athletic monitoring.

The effect of pedalling cadence on respiratory frequency: passive vs. active exercise of different intensities

PURPOSE

Pedalling cadence influences respiratory frequency (f_R) during exercise, with group III/IV muscle afferents possibly mediating its effect. However, it is unclear how exercise intensity affects the link between cadence and f_R. We aimed to test the hypothesis that the effect of cadence on f_R is moderated by exercise intensity, with interest in the underlying mechanisms.

METHODS

Ten male cyclists performed a preliminary ramp incremental test and three sinusoidal experimental tests on separate visits. The experimental tests consisted of 16 min of sinusoidal variations in cadence between 115 and 55 rpm (sinusoidal period of 4 min) performed during passive exercise (PE), moderate exercise (ME) and heavy exercise (HE). The amplitude (A) and phase lag (φ) of the dependent variables were calculated.

RESULTS

During PE, f_R changed in proportion to variations in cadence (r = 0.85, P < 0.001; A = 3.9 ± 1.4 breaths·min^-1; φ = - 5.3 ± 13.9 degrees). Conversely, the effect of cadence on f_R was reduced during ME (r = 0.73, P < 0.001; A = 2.6 ± 1.3 breaths·min^-1; φ = - 25.4 ± 26.3 degrees) and even more reduced during HE (r = 0.26, P < 0.001; A = 1.8 ± 1.0 breaths·min^-1; φ = - 70.1 ± 44.5 degrees). No entrainment was found in any of the sinusoidal tests.

CONCLUSION

The effect of pedalling cadence on f_R is moderated by exercise intensity-it decreases with the increase in work rate-and seems to be mediated primarily by group III/IV muscle afferents, at least during passive exercise.

Heart rate variability during high-intensity field exercise in female distance runners

The purposes of this study were to demonstrate the transition of heart rate variability (HRV) during trials in the field and to examine the relationship between peak frequency of high-frequency band (HF) and stride frequency. Ten healthy long-distance college female runners (age 19-21 years) performed a 3000 m realistic time trial. The time-series power spectrum analysis by maximum entropy method was used to evaluate cardiac autonomic nervous activity during the race. Cross-correlation coefficients were calculated to estimate the degree of linear co-ordination between the central peak frequency of HF and stride frequency. Just after starting, the decrease in HF (0.15-1.00 Hz) and a transient increase of low-frequency band (LF)/HF were found. After that, the HF remained at a low level and LF/HF decreased sharply. These findings suggested that the parasympathetic activity was suppressed and sympathetic activity increased just after starting, and the sympathetic activity reached the saturated level according to continuation of high-intensity exercise. In spite of the significant decrease of HRV during trials, peak frequency of HF could be differentiated clearly. The cross-correlation coefficient of peak frequency of HF and stride frequency was from 0.703 to 0.868. This finding indicated that exercise rhythm reflected HRV during high-intensity running in the field.

The effect of exercise modality on respiratory muscle performance in triathletes

PURPOSE

The aim of this study was to examine the effects of the cycle-run and run-cycle successions of the triathlon and duathlon, respectively, on respiratory muscle strength and endurance.

METHODS

Respiratory muscle strength was assessed by measuring maximal inspiratory (P(Imax)) and expiratory (P(Emax)) pressures. Respiratory muscle endurance was assessed by measuring the time limit (T(lim)). Twelve triathletes participated in a three-trial protocol. The first trial consisted of an incremental cycle test to assess the maximal oxygen uptake (.VO(2max)) of triathletes. Trial 2 consisted of 20 min of cycling followed by 20 min of running (C-R), and trial 3 consisted of 20 min of running followed by 20 min of cycling (R-C). Trials 2 and 3 were performed at the same metabolic intensity (%.VO(2max)). P(Imax) and P(Emax) were measured before and 10 min after C-R and R-C, and 1 min after the post-C-R and post-R-C T(lim) measurements (P(Imax) 1'). T(lim) was measured 1 d before and 30 min after C-R and R-C.

RESULTS

The results showed a significant decrease in P(Imax) after C-R (126.7 +/- 4.3 cmH(2)O, P < 0.05) and R-C (123.7 +/- 4.9 cmH(2)O, P < 0.05) compared with the baseline values (130 +/- 3.8 and 129.6 +/- 4.3 cmH(2)O, respectively). P(Imax) 1' showed a significantly greater decrease after R-C versus C-R (111.2 +/- 5.5 cmH(2)O vs 121.2 +/- 3.9 cmH(2O), respectively, P < 0.001). Tlim after C-R (3.3 +/- 0.3 min) and R-C (2.1 +/- 0.3 min) decreased significantly compared with baseline values (4.19 +/- 0.3 min and 4.02 +/- 0.3 min, respectively). However, the Tlim decrease after R-C was significantly greater than after C-R (P < 0.001).

CONCLUSION

We concluded that respiratory muscle strength and endurance were less decreased after the cycle-run succession and that cycling induced a greater decrease in respiratory muscle endurance than running.

Ventilation and locomotion coupling in varsity male rowers

Ventilation and locomotion coupling (entrainment) has been observed and described in rowers during incremental exercise protocols but not during simulated race conditions. The purpose of this descriptive study was to examine ventilation and locomotion entrainment on a breath-by-breath and stroke-by-stroke basis in varsity male rowers during a maximal 2,000-m ergometer test. Eight of eleven rowers entrained ventilation at integral multiples of stroke rate (1:1, 2:1, or 3:1) for at least 120 consecutive seconds, with a 2:1 entrainment pattern being most common. In all 2:1-entrained subjects, inspiration occurred at catch and finish and expiration occurred during the latter portions of drive and recovery. In entrained and unentrained breaths from all rowers, peak flow rates and tidal volumes varied depending on when the breath was initiated during the stroke cycle. Entrained rowers made use of these differences and breathed in a pattern by which they avoided initiating breaths that resulted in reduced tidal volumes. The present data indicated that ventilation was impaired at stroke finish and not at catch, as hypothesized by some previous researchers. Ventilation also appeared to be subordinate to consistent locomotive patterns under race conditions.

Ventilation and entrainment of breathing during cycling and running in triathletes

PURPOSE

To assess whether entrainment of breathing (E) during exercise: 1) differed according to the test protocol in well-trained triathletes, and 2) improved ventilatory efficiency during exercise.

METHODS

Eight triathletes performed three incremental tests until exhaustion: while cycling (CE), while running at increasing grade and constant speed (increasing GRADE) and while running at increasing speed and constant grade (increasing SPEED), respectively. E was evaluated as the percentage of breaths occurring at respiratory rates (F) corresponding to integer ratios of the exercise cycle rate. To assess whether E improved ventilatory efficiency, deltaVE/VO2 between nonentrained and entrained breaths was measured at each load.

RESULTS

Mean E was higher in CE (57.2+/-21.9%) than in increasing GRADE (46.9+/-18.7%) and increasing SPEED (41.4+/-17.2%). E decreased at high loads in CE and increasing SPEED but not in increasing GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as VO2Tvent/VO2peak%) only during increasing GRADE. By multiple regression analysis on all data, minute ventilation correlated with CO2 production but not with the exercise cycle rate; however, either F or tidal volume correlated significantly with both these variables. VE/VO2 was lower in entrained than nonentrained breaths at each load in CE and increasing GRADE experiments, but the difference was small.

CONCLUSIONS

In spite of some differences among protocols, triathletes showed significant E during incremental exercise tests. Spontaneous E appeared to slightly improve ventilatory efficiency during CE and increasing GRADE protocols.

Increased ventilation in runners during running as compared to walking at similar metabolic rates

At similar levels of carbon dioxide production (VCO2) and oxygen consumption (VO2), runners have been shown to have a greater minute ventilation (VE) during running as compared to walking. The mechanism responsible for these differences has yet to be identified. To determine if these differences are a result of differences in acid-base status, potassium (K+), norepinephrine and/or epinephrine levels, seven well-trained runners completed walk and run tests at similar VO2 and VCO2 levels. The occurrence of entrainment of the breathing and stride frequencies during both walking and running was also determined. VE was significantly greater during the run as compared to the walk, 73.7 (2.2) versus 68.6 (2.0) l.min-1, respectively, despite the similarity in VO2 and VCO2 levels. Alveolar ventilation was not significantly different between the run and the walk, 60.4 (4.7) versus 59.6 (4.4) l.min-1, respectively. Dead space ventilation was found to be significantly greater during running as compared to walking, 13.3 (3.2) versus 9.0 (4.7) l.min-1, respectively. The increases in VE were due to increases in breathing frequency and decreases in tidal volume during the run as compared to the walk. Arterial partial pressures of CO2 (PaCO2) were not significantly different when comparing walking and running to rest values nor when comparing walking and running. Arterial pH was significantly lower during walking as compared to rest and running. Bicarbonate levels were significantly lower during walking as compared to rest. Lactate was significantly greater during walking as compared to rest and to running. K+ levels were significantly higher during walking and running as compared to rest. Epinephrine and norepinephrine levels were not significantly different between running and walking. During the walk, six of the seven subjects entrained their breathing frequency to the stride frequency, and during the run three of the seven subjects demonstrated entrainment. Results from this investigation do not support mediation of VE under the present experimental conditions by changes in arterial levels of humoral factors previously shown to influence VE.

Ventilatory responses during arm and leg exercise at varying speeds and forces in untrained female humans

1. Involvement of neural stimuli, central and/or peripheral in origin, in exercise ventilatory control was ascertained by examining the ventilatory responses to varying mechanical conditions of arm and leg cycle ergometries. Twelve untrained women underwent each of two modes of exercise at three levels of loading (0, 5 and 10 N), each at three levels of speed (30, 50 and 72 r.p.m.), during which steady-state values of minute ventilation (VE), tidal volume (VT), respiratory frequency (f) and CO2 excretion (VCO2) were measured. 2. Using the data obtained at the aerobic work intensities, the relationship of ventilatory responses (VE, VT and f) to the metabolic (VCO2) and mechanical (speed and load) variables were studied by multiple linear regression analysis. Coefficient of determination (r2) of the regression model was lowest (0.84) for f in the arm exercise and highest (0.99) for VE in the leg exercise. 3. Standardized partial regression coefficients of the model indicated that VE response is related to VCO2 at the rate of 94 +/- 3% (mean +/- S.E.M.) and to the pedal rate at 8 +/- 3% during the leg exercise, while it is closely related to VCO2 in the arm exercise. For f response, influence of the rate of limb movement was seen in the leg exercise but not in the arm exercise. The different effects of the rate of limb movement between the two exercise modes may be related to familiarity with the exercise modes, suggesting that a familiarity-related mechanism is involved in exercise ventilatory control. 4. A heavier load imposed on the limb muscles elicited a greater VT both in the arm and leg exercise and a lower f in the arm exercise. Postural control in the upper torso during increased limb muscle tension seems to affect VT and f.