Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Supervised exercise (SE) in patients with type 2 diabetes improves oxygen uptake kinetics at the onset of exercise. Maintenance of these improvements, however, has not been examined when supervision is removed. We explored if potential improvements in oxygen uptake kinetics following a 12-week SE that combined aerobic and resistance training were maintained after a subsequent 12-week unsupervised exercise (UE). The involvement of cardiac output (CO) in these improvements was also tested. Nineteen volunteers with type 2 diabetes were recruited. Oxygen uptake kinetics and CO (inert gas rebreathing) responses to constant-load cycling at 50% ventilatory threshold (V_T), 80% V_T, and mid-point between V_T and peak workload (50% Δ) were examined at baseline (on 2 occasions) and following each 12-week training period. Participants decided to exercise at a local gymnasium during the UE. Thirteen subjects completed all the interventions. The time constant of phase 2 of oxygen uptake was significantly faster (p < 0.05) post-SE and post-UE compared with baseline at 50% V_T (17.3 ± 10.7 s and 17.5 ± 5.9 s vs. 29.9 ± 10.7 s), 80% V_T (18.9 ± 4.7 and 20.9 ± 8.4 vs. 34.3 ± 12.7s), and 50% Δ (20.4 ± 8.2 s and 20.2 ± 6.0 s vs. 27.6 ± 3.7 s). SE also induced faster heart rate kinetics at all 3 intensities and a larger increase in CO at 30 s in relation to 240 s at 80% V_T; and these responses were maintained post-UE. Unsupervised exercise maintained benefits in oxygen uptake kinetics obtained during a supervised exercise in subjects with diabetes, and these benefits were associated with a faster dynamic response of heart rate after training.

Muscle damage slows oxygen uptake kinetics during moderate-intensity exercise performed at high pedal rate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of aerobic endurance training status and specificity on oxygen uptake kinetics during maximal exercise

The main purpose of this study was to analyze the effects of exercise mode, training status and specificity on the oxygen uptake ((V)over dot O-2) kinetics during maximal exercise performed in treadmill running and cycle ergometry. Seven runners (R), nine cyclists (C), nine triathletes (T) and eleven untrained subjects (U), performed the following tests on different days on a motorized treadmill and on a cycle ergometer: (1) incremental tests in order to determine the maximal oxygen uptake ((V)over dot O-2max) and the intensity associated with the achievement of (V)over dot O-2max (I(V)over dot O-2max); and (2) constant work-rate running and cycling exercises to exhaustion at I(V)over dot O-2max to determine the effective time constant of the (V)over dot O-2 response (tau(V)over dot O-2). Values for (V)over dotO(2max) obtained on the treadmill and cycle ergometer [R=68.8 (6.3) and 62.0 (5.0); C=60.5 (8.0) and 67.6 (7.6); T=64.5 (4.8) and 61.0 (4.1); U=43.5 (7.0) and 36.7 (5.6); respectively] were higher for the group with specific training in the modality. The U group showed the lowest values for VO2max, regardless of exercise mode. Differences in tau(V)over dot O-2 (seconds) were found only for the U group in relation to the trained groups [R=31.6 (10.5) and 40.9 (13.6); C=28.5 (5.8) and 32.7 (5.7); T=32.5 (5.6) and 40.7 (7.5); U=52.7 (8.5) and 62.2 (15.3); for the treadmill and cycle ergometer, respectively]; no effects of exercise mode were found in any of the groups. It is concluded that tauVO(2) during the exercise performed at I(V)over dot O-2max is dependent on the training status, but not dependent on the exercise mode and specificity of training. Moreover, the transfer of the training effects on tau(V)over dotO(2) between both exercise modes may be higher compared with (V)over dot O-2max.

Oxygen uptake kinetics and time to exhaustion in cycling and running: A comparison between trained and untrained subjects

The objective of the present study was to compare pulmonary gas exchange kinetics (VO 2 kinetics) and time to exhaustion (Tlim) between trained and untrained individuals during severe exercise performed on a cycle ergometer and treadmill. Eleven untrained males in running (UR) and cycling (UC), nine endurance cyclists (EC), and seven endurance runners (ER) were submitted to the following tests on separate days: (i) incremental test for determination of maximal oxygen uptake (VO 2max) and the intensity associated with the achievement of VO 2max (IVO 2max) on a mechanical braked cycle ergometer (EC and UC) and on a treadmill (ER and UR); (ii) all-out exercise bout performed at IVO 2max to determine the time to exhaustion at IVO 2max (Tlim) and the time constant of oxygen uptake kinetics (τ). The τ was significantly faster in trained group, both in cycling (EC = 28.2 ± 4.7 s; UC = 63.8 ± 25.0 s) and in running (ER = 28.5 ± 8.5 s; UR = 59.3 ± 12.0 s). Tlim of untrained was significantly lower in cycling (EC = 384.4 ± 66.6 s vs. UC; 311.1 ± 105.7 s) and higher in running (ER = 309.2 ± 176.6 s vs. UR = 439.8 ± 104.2 s). We conclude that the VO 2 kinetic response at the onset of severe exercise, carried out at the same relative intensity is sensitive to endurance training, irrespective of the exercise type. The endurance training seems to differently influence Tlim during exercise at IVO 2max in running and cycling. © 2003 Taylor & Francis Ltd.

The Positive Effects of Priming Exercise on Oxygen Uptake Kinetics and High-Intensity Exercise Performance Are Not Magnified by a Fast-Start Pacing Strategy in Trained Cyclists

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The effect of prior exercise intensity on oxygen uptake kinetics during high-intensity running exercise in trained subjects

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prior Heavy-Intensity Exercise's Enhancement of Oxygen-Uptake Kinetics and Short-Term High-Intensity Exercise Performance Independent of Aerobic-Training Status

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Walking performance, oxygen uptake kinetics and resting muscle pyruvate dehydrogenase complex activity in peripheral arterial disease

In the present study, we tested the hypothesis that walking intolerance in intermittent claudication (IC) is related to both slowed whole body oxygen uptake (Vo(2)) kinetics and altered activity of the active fraction of the pyruvate dehydrogenase complex (PDCa) in skeletal muscle. Ten patients with IC and peripheral arterial disease [ankle/brachial index (ABI) = 0.73 +/- 0.13] and eight healthy controls (ABI = 1. 17 +/- 0.13) completed three maximal walking tests. From these tests, averaged estimates of walking time, peak Vo(2) and the time constant of Vo(2) (tau) during submaximal walking were obtained. A muscle sample was taken from the gastrocnemius medialis muscle at rest and analysed for PDCa and several other biochemical variables. Walking time and peak Vo(2) were approx. 50 % lower in patients with IC than controls, and tau was 2-fold higher (P < 0.05). r was significantly correlated with walking time (r = -0.72) and peak Vo(2) (r = -0.66) in patients with IC, but not in controls. PDCa was not significantly lower in patients with IC than controls; however, PDCa tended to be correlated with tau (r = -0.56, P = 0.09) in patients with IC, but not in controls (r = -0.14). A similar correlation was observed between resting ABI and tau (r = -0.63, P = 0.05) in patients with IC. These data suggest that the impaired Vo(2) kinetics contributes to walking intolerance in IC and that, within a group of patients with IC, differences in Vo(2) kinetics might be partly linked to differences in muscle carbohydrate oxidation.

Locomotor Muscle Fatigue Does Not Alter Oxygen Uptake Kinetics during High-Intensity Exercise

The V˙O2 slow component (V˙O2sc) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre-fatigue condition) or rest for 33 min (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-s maximal sprints at a fixed pedaling cadence of 90 rev·min−1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and V˙O2max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03), the V˙O2sc was not significantly different between the pre-fatigue (464 ± 301 mL·min−1) and the control (556 ± 223 mL·min−1) condition (P = 0.50). Blood lactate response was not significantly different between conditions (P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01) suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the V˙O2 kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the V˙O2sc is strongly associated with locomotor muscle fatigue.

Reliability of peak O-2 uptake and O-2 uptake kinetics in step exercise tests in healthy subjects

To date little is known about the reliability of peak oxygen consumption (VO2pEAK) in incremental metronome paced step tests (1ST) and the reliability of on-kinetics VO2 has never been studied. We aimed to study the reliability of both tests. Eleven healthy subjects performed two ISTs until exhaustion. On two different days two duplicate 4 min constant metronome paced step tests (CST) were performed. VO2PEAK, mean response time (MRT) and phase II time constant (tau) were tested for reproducibility using the paired t-tests, in addition to the limits of agreement (LOA) and within subject coefficient of variation (COV). With a 95% LOA of 0.38 to 0.26 L min(-1), -8.7 to 9.1 s and -9.9 to 10.5 s they exhibit a COV of 3%, 4.5% and 6.9% for VO2PEAK, MRT and tau respectively. ST are sufficiently reliable for maximal and submaximal aerobic power assessments in healthy subjects and new studies of oxygen uptake kinetics in selected patient groups are warranted. (C) 2014 Elsevier B.V. All rights reserved.

Effects of Exercise Mode on the Oxygen Uptake Kinetic Response to Severe-Intensity Exercise in Prepubertal Children

The objective of this study was to verify the effect of the exercise mode on slow component of VO(2) (VO(2)SC) in children aged 11-12 years during severe-intensity exercise. After determination of the lactate threshold (LT) and peak VO(2) (VO(2)peak) in both cycling (CE) and running exercise (TR), fourteen active boys completed a series of "square-wave" transitions of 6-min duration at 75%Delta [75%Delta = LT + 0.75 X (VO(2)peak-LT)l to determine the VO(2) kinetics. The VO(2)SC was significantly higher in CE (180.5 +/- 155.8 ml . min(-1)) than in TR (113.0 +/- 84.2 ml . min(-1)). We can conclude that, although a VO(2)SC does indeed develop during TR in children, its magnitude is considerably lower than in CE during severe-intensity exercise.

Electromyographic activity in lower limb muscles is temporally associated with the slow phase of oxygen uptake during cycling

Although the "slow" phase of pulmonary oxygen uptake (Vo2) appears to represent energetic processes in contracting muscle, electromyographic evidence tends not to support this. The present study assessed normalized integrated electromyographic (NIEMG) activity in eight muscles that act about the hip, knee and ankle during 8 min of moderate (ventilatory threshold) cycling in six male cyclists. (Vo2) was measured breath by breath during four repeated trials at each of the two intensities. Moderate and very heavy exercise followed a 4-min period of light exercise (50 W). During moderate exercise the slow (Vo2) phase was absent and NIEMG in all muscles did not increase after the first minute of exercise. During very heavy exercise, the slow phase emerged (time delay=58 ± 16 s) and increased progressively (time constant=120 ± 35 s) to an amplitude (0.83 ± 0.16 L/min) that was approximately 21% of the total (Vo2) response. This slow (Vo2) phase coincided with a significant increase in NIEMG in most muscles, and differences in NIEMG activities between the two intensities revealed "slow" muscle activation profiles that differed between muscles in terms of the onset, amplitude and shape of these profiles. This supports the hypothesis that the slow (Vo2) phase is a function of these different slow muscle activation profiles.