High-intensity Continuous Exercise Research Articles

The Effect of Different Exercise Modalities on Sertoli-germ Cells Metabolic Interactions in High-fat Diet-induced Obesity Rat Models: Implication on Glucose and Lactate Transport, Igf1, and Igf1R-dependent Pathways.

The study aimed to uncover a unique aspect of obesity-related metabolic disorders in the testicles induced by a high-fat diet (HFD) and explored the potential mitigating effects of exercise modalities on male fertility. Thirty mature male Wistar rats were randomly assigned to control, HFD-sole, moderate-intensity exercise with HFD (HFD+MICT), high-intensity continuous exercise with HFD (HFD+HICT), and high-intensity interval exercise with HFD (HFD+HIIT) groups (n=6/group). Intracytoplasmic carbohydrate (ICC) storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and testicular lactate and lactate dehydrogenase (LDH) levels were assessed. ICC storage significantly decreased in HFD-sole rats, along with decreased mRNA and protein levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R. The HFD-sole group exhibited a notable reduction in testicular lactate and LDH levels (p<0.05). Conversely, exercise, particularly HIIT, upregulated ICC storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and enhanced testicular lactate and LDH levels. These results confirm that exercise, especially HIIT, has the potential to mitigate the adverse effects of HFD-induced obesity on testicular metabolism and male fertility. The upregulation of metabolite transporters, LDH, lactate levels, Igf1, and Igf1R expression may contribute to maintaining metabolic interactions and improving the glucose/lactate conversion process. These findings underscore the potential benefits of exercise in preventing and managing obesity-related male fertility issues.

Effects of Acute High-Intensity Interval Exercise and High-Intensity Continuous Exercise on Inhibitory Function of Overweight and Obese Children.

This study aimed to examine whether a single bout each of high-intensity interval exercise (HIIE) and high-intensity continuous exercise (HICE) could improve inhibitory functions of overweight and obese children, and which mode of exercise was more beneficial. Seventy-two overweight and obese children, with (26.02 ± 1.05 kg/m2), aged 10–14 years (11.56 ± 1.03 years), were randomly assigned to three groups. The HIIE group completed a 30-min treadmill exercise session (5-min warm up, 20-min HIIE, and 5-min cool-down). The HICE group performed 30 min of rope skipping, while the control (CON) group watched a designated cartoon on a tablet computer for the same duration. Reaction time and number of errors in the Stroop test were determined before and after the intervention. The difference between pre- and post-test reaction time scores was higher in the HIIE and HICE groups than in the CON group, while the pre- and post-test difference in the number of errors was similar between groups. Overall, it is likely that both acute HIIE and HICE were similarly efficient in facilitating cognitive and inhibitory functions of children with overweight and obesity conditions, supporting the benefits of acute high-intensity exercise probability for cognitive functions of children in general, as well as of the population with overweight and obesity conditions.

Salivary And Plasmatic Creatine Kinase And Lactate Dehydrogenase Responses Following High-intensity Continuous Exercise

Salivary And Plasmatic Creatine Kinase And Lactate Dehydrogenase Responses Following High-intensity Continuous Exercise

Capsaicin Supplementation during High-intensity Continuous Exercise: A Double-blind Study.

To investigate the effect of acute capsaicin (CAP) supplementation on time to exhaustion, physiological responses and energy systems contribution during continuous high-intensity exercise session in runners. Fifteen recreationally-trained runners completed two randomized, double-blind continuous high-intensity exercises at the speed eliciting 90% V̇O2peak (90% s V̇O2peak), 45 minutes after consuming capsaicin or an isocaloric placebo. Time to exhaustion, blood lactate concentration, oxygen consumption during and 20-min post-exercise, energy systems contribution, time to reach V̇O2peak, heart rate and the rate of perceived exertion (RPE) were evaluated. There was no significant difference between conditions for time to reach V̇O2peak (CAP:391.71±221.8 vs. PLA:298.20±174.5 sec, ES:0.58, p=0.872), peak lactate (CAP:7.98±2.11 vs. PLA:8.58±2.15 µmol, ES:-0.28, p=0.257), time to exhaustion (CAP:654.28±195.44 vs. PLA:709.20±208.44 sec, ES:-0.28, p=0.462, end-of-exercise heart rate (CAP:177.6±14.9 vs. PLA:177.5±17.9 bpm, ES:-0.10, p=0.979) and end-of-exercise RPE (CAP: 19±0.8 vs. PLA: 18±2.4, ES: 0.89, p=0.623). In conclusion, acute CAP supplementation did not increase time to exhaustion during high-intensity continuous exercise nor alter physiological responses in runners.

Influence of personality and self-efficacy on perceptual responses during high-intensity interval exercise in adolescents

Inter-individual cognitive factors have been shown to be related to the changes in affect evaluations during continuous high-intensity exercise in adolescents, but the role of cognitive factors on affect during high-intensity interval exercise (HIIE) is currently unknown. This study evaluated the influence of personality traits (behavioral activation system; BAS and behavioral inhibition system; BIS) and self-efficacy on affect, enjoyment and perceived exertion during HIIE in adolescents. Participants (n = 30; 15 boys; mean age = 12.2 ± 0.4 years; moderate to vigorous physical activity levels per day = 33 ± 12 min) were median split into low vs. high BAS/BIS and self-efficacy groups. All participants performed HIIE consisting of 8 × 1-min work-intervals at 85% of peak power separated by 75 s recovery. Affect, enjoyment, and rating of perceived exertion (RPE) were recorded 5 min before HIIE, near the end of the HIIE work intervals, and 20 min after HIIE. The high BAS/low BIS group elicited greater affect and enjoyment compared to low BAS/high BIS group during work-intervals 5–8 (all p < 0.039, all ES > 0.59) and after HIIE for post-enjoyment (all p < 0.038, all ES > 0.95). Affect and enjoyment were greater in high compared to low self-efficacy group during work-intervals 5–8 (all p < 0.048, all ES > 0.62). The BAS/BIS groups elicited similar RPE (all p > 0.10), but RPE was lower in high than low self-efficacy group at work-intervals 5–8 (all p < 0.037, ES > 0.98). Individual differences in personality and self-efficacy may influence the affective, enjoyment and RPE responses during HIIE in adolescents. Lay summary: This study aimed to evaluate the role of personality characteristics and self-efficacy on perceptual responses (pleasure/displeasure and enjoyment) during HIIE in youth. Individual differences in personality characteristics and self-efficacy may decrease or increase the likelihood that a person will experience pleasurable feelings and enjoyment to HIIE in youth.

Dynamic Cerebral Autoregulation Is Maintained during High-Intensity Interval Exercise.

High-intensity interval exercise (HIIE) is more effective at increasing metabolic and cardiovascular health compared with moderate-intensity continuous exercise for patients with cardiovascular disease, but exhaustive high-intensity continuous exercise attenuates dynamic cerebral autoregulation (CA). This study assessed the effect of HIIE on dynamic CA. Nine healthy men (age, 24 ± 3 yr; mean ± SD) warmed up at 50%-60% maximal workload (Wmax) for 5 min before HIIE including four 4-min bouts of exercise at 80%-90% Wmax interspaced by four 3-min bouts at 50% to 60% Wmax. Transcranial Doppler determined middle cerebral artery mean blood velocity (MCA Vmean), and brachial artery catheterization determined mean arterial pressure (MAP). Dynamic CA was evaluated by transfer function analysis of changes in MAP and MCA Vmean. The HIIE increased MAP (from 92 ± 9 to 104 ± 10 mm Hg; P < 0.0125), whereas MCA Vmean did not change. Transfer function phase increased and coherence decreased during HIIE (P < 0.0125 vs rest, respectively), whereas gain was unchanged. The results suggest that dynamic CA is unaffected during HIIE, indicating that the brain is protected from fluctuations in MAP. Thus, we propose that HIIE may be beneficial for brain-related health as maintenance of cerebral perfusion in contrast to high-intensity continuous exercise.

Physiological resolution of periodic breath holding during heavy-intensity Fartlek exercise.

The purpose was to compare the singular and combined effects of 5s breath holds (BH) and 5s sprints, every 30s, during continuous high-intensity exercise, on ventilation ([Formula: see text]), oxygen uptake ([Formula: see text]O2) and associated kinetics (τ), carbon dioxide production ([Formula: see text]CO2), and arterialized-capillary lactate concentration ([La-]). Ten men (24 ± 3years) performed 4-6min ergometer protocols that included a step-transition from 20W to a power output of 50% of the difference between lactate threshold and [Formula: see text]O2 peak (Δ50%) including: (1) a continuous protocol (CONT) with free breathing, (2) an intermittent BH protocol (CONT-BH); repeated cycles of 5s BH: 25s free breathing, (3) a Fartlek protocol (Fartlek); repeated 5s at peak aerobic power output: 25s at Δ50%; (4) combining the 5s Fartlek and CONT-BH protocol (Fartlek-BH). Breath-by-breath gas exchange, measured by mass spectrometry and turbine, was recorded. [Formula: see text] E (Lmin-1) was greater (p < 0.05) than CONT (90 ± 7) in all conditions CONT-BH (98 ± 16), Fartlek (105 ± 10), and Fartlek-BH (101 ± 19). [Formula: see text]O2 and [Formula: see text]CO2 (Lmin-1) were unchanged in CONT-BH (2.73 ± 0.14 and 3.16 ± 0.38) and greater in Fartlek (2.85 ± 0.12 and 3.43 ± 0.16), compared to CONT (2.71 ± 0.12 and 3.12 ± 0.13). Whereas, [Formula: see text]CO2 during Fartlek-BH was higher (3.28 ± 0.35) and [Formula: see text]O2 was unchanged (2.73 ± 0.14). Fartlek-BH resulted in slower [Formula: see text]O2 kinetics (62.2 ± 19s) and greater blood lactate concentrations (11.5 ± 2.7mM), compared to CONT (48.8 ± 12s; 9.0 ± 2.3mM, respectively). It was demonstrated that the CONT-BH resulted in increased ventilation that sustained [Formula: see text]O2. However, [Formula: see text]O2 was restricted when an additional work was combined with the BH condition.

Perceptual Responses to High- and Moderate-Intensity Interval Exercise in Adolescents.

Continuous high-intensity exercise is proposed to evoke unpleasant sensations as predicted by the dual-mode theory and may negatively impact on future exercise adherence. Previous studies support unpleasant sensations in affective responses during continuous high-intensity exercise, but the affect experience during high-intensity interval exercise (HIIE) involving brief bursts of high-intensity exercise separated by low-intensity activity is poorly understood in adolescents. We examined the acute affective, enjoyment, and perceived exertion responses to HIIE compared with moderate-intensity interval exercise (MIIE) in adolescents. Thirteen adolescent boys (mean ± SD: age, 14.0 ± 0.5 yr) performed two counterbalanced exercise conditions: 1) HIIE: 8 × 1-min work intervals at 90% maximal aerobic speed; and 2) MIIE: between 9 and 12 × 1-min work intervals at 90% ventilatory threshold where the number of intervals performed were distance-matched to HIIE. HIIE and MIIE work intervals were interspersed with 75 s active recovery at 4 km·h. Affect, enjoyment, and RPE were recorded before, during, and after exercise. Affect responses declined in both conditions but the fall was greater in HIIE than MIIE (P < 0.025, effect size [ES], 0.64 to 0.81). Affect remained positive at the end-work interval for both conditions (MIIE, 2.62 ± 1.50; HIIE, 1.15 ± 2.08 on feeling scale). No enjoyment differences were evident during HIIE and MIIE (P = 0.32), but HIIE elicited greater postexercise enjoyment compared with MIIE (P = 0.01, ES = 0.47). RPE was significantly higher during HIIE than MIIE across all work intervals (all P < 0.03, ES > 0.64). Despite elevated RPE, HIIE did not elicit prominent unpleasant feelings as predicted by the dual-mode theory and was associated with greater postexercise enjoyment responses than MIIE. This study demonstrates the feasibility of the application of HIIE as an alternative form of physical activity in adolescents.

Comparison of affective responses during and after low volume high-intensity interval exercise, continuous moderate- and continuous high-intensity exercise in active, untrained, healthy males

ABSTRACTThis study compared affective responses to low volume high-intensity interval exercise (HIIE), moderate-intensity continuous exercise (MICE) and high-intensity continuous exercise (HICE). Twelve untrained males ( 48.2 ± 6.7 ml·kg−1·min−1) completed MICE (30 min cycle at 85% of ventilatory threshold (VT)), HICE (cycle at 105% of VT matched with MICE for total work), and HIIE (10 x 6 s cycle sprints with 60 s recovery). Affective valence and perceived activation were measured before exercise, post warm-up, every 20% of exercise time, and 1, 5, 10, and 15 min post-exercise. Affective valence during exercise declined by 1.75 ± 2.42, 1.17 ± 1.99, and 0.42 ± 1.38 units in HICE, HIIE, and MICE, respectively, but was not statistically influenced by trial (P = 0.35), time (P = 0.06), or interaction effect (P = 0.08). Affective valence during HICE and HIIE was consistently less positive than MICE. Affective valence post-exercise was not statistically influenced by trial (P = 0.10) and at 5 min post-exercise exceeded end-exercise values (P = 0.048). Circumplex profiles showed no negative affect in any trial. Affective responses to low volume HIIE are similar to HICE but remain positive and rebound rapidly, suggesting it may be a potential alternative exercise prescription.

Salbutamol effects on systemic potassium dynamics during and following intense continuous and intermittent exercise.

Salbutamol inhalation is permissible by WADA in athletic competition for asthma management and affects potassium regulation, which is vital for muscle function. Salbutamol effects on arterial potassium concentration ([K+]a) during and after high-intensity continuous exercise (HIcont) and intermittent exercise comprising repeated, brief sprints (HIint), and on performance during HIint are unknown and were investigated. Seven recreationally active men participated in a double-blind, randomised, cross-over design, inhaling 1000µg salbutamol or placebo. Participants cycled continuously for 5min at 40% [Formula: see text]O2peak and 60% [Formula: see text]O2peak, then HIcont (90s at 130% [Formula: see text]O2peak), 20min recovery, and then HIint (3 sets, 5×4s sprints), with 30min recovery. Plasma [K+]a increased throughout exercise and subsequently declined below baseline (P<0.001). Plasma [K+]a was greater during HIcont than HIint (P<0.001, HIcont 5.94±0.65 vs HIint set 1, 4.71±0.40mM); the change in [K+]a from baseline (Δ[K+]a) was 2.6-fold greater during HIcont than HIint (P<0.001). The Δ[K+] throughout the trial was less with salbutamol than placebo (P<0.001, treatment main effect, 0.03±0.67 vs 0.22±0.69mM, respectively); and remained less after correction for fluid shifts (P<0.001). The Δ[K+] during HIcont was less after salbutamol (P<0.05), but not during HIint. Blood lactate, plasma pH, and the work output during HIint did not differ between trials. Inhaled salbutamol modulated the [K+]a rise across the trial, comprising intense continuous and intermittent exercise and recovery, lowering Δ[K+] during HIcont. The limited [K+]a changes during HIint suggest that salbutamol is unlikely to influence systemic [K+] during periods of intense effort in intermittent sports.

Oxygen uptake, respiratory exchange ratio, or total distance: a comparison of methods to equalize exercise volume in Wistar rats.

This study compared strategies to equalize the volume of aerobic exercise performed with different intensities by Wistar rats, based on the distance covered during exercise bouts and energy expenditure (EE, isocaloric sessions) obtained from oxygen uptake (V̇O2) or respiratory exchange ratio (RER). Thirty-three male rats (270.5±12.8 g) underwent maximal exercise tests to determine V̇O2 reserve (V̇O2R), being randomly assigned to three groups: moderate-intensity continuous exercise at speed corresponding to 50% V̇O2R (MIC; n=11); high-intensity continuous exercise at 80% V̇O2R (HIC; n=11); and high-intensity intermittent exercise (HII; n=11) at 60% V̇O2R (3 min) and 80% V̇O2R (4 min). Exercise duration was calculated individually to elicit EE of 5 kcal in each session. No difference between groups was found for total running distance (MIC: 801±46, HIC: 734±42, HII: 885±64 m; P=0.13). Total EE measured by RER was systematically underestimated compared to values obtained from V̇O2 (HII: 4.5% and MIC: 6.2%, P<0.05). Total EE (calculated from V̇O2), and duration of HIC bouts (2.8 kcal and 30.8±2.2 min) were lower (P<0.0001) than in MIC (4.9 kcal and 64.7±1.8 min) and HII (4.7 kcal and 46.9±2.2 min). Predicted and actual values of total V̇O2, total EE, and duration of isocaloric sessions were similar in MIC and HII (P>0.05), which were both higher than in HIC (P<0.0001). In conclusion, the time to achieve a given EE in exercise bouts with different intensities did not correspond to the total distance. Therefore, the volume of aerobic exercise in protocols involving Wistar rats should be equalized using EE rather than total covered distance.

Endothelial function does not improve with high-intensity continuous exercise training in SHR: implications of eNOS uncoupling.

Exercise training is a well-recognized way to improve vascular endothelial function by increasing nitric oxide (NO) bioavailability. However, in hypertensive subjects, unlike low- and moderate-intensity exercise training, the beneficial effects of continuous high-intensity exercise on endothelial function are not clear, and the underlying mechanisms remain unknown. The aim of this study was to investigate the impact of high-intensity exercise on vascular function, especially on the NO pathway, in spontaneous hypertensive rats (SHR). These effects were studied on WKY, sedentary SHR and SHR that exercised at moderate (SHR-MOD) and high intensity (SHR-HI) on a treadmill (1 h per day; 5 days per week for 6 weeks at 55% and 80% of their maximal aerobic velocity, respectively). Endothelial function and specific NO contributions to acetylcholine-mediated relaxation were evaluated by measuring the aortic ring isometric forces. Endothelial nitric oxide synthase (eNOS) expression and phosphorylation (ser1177) were evaluated by western blotting. The total aortic and eNOS-dependent reactive oxygen species (ROS) production was assessed using electron paramagnetic resonance in aortic tissue. Although the aortas of SHR-HI had increased eNOS levels without alteration of eNOS phosphorylation, high-intensity exercise had no beneficial effect on endothelium-dependent vasorelaxation, unlike moderate exercise. This result was associated with increased eNOS-dependent ROS production in the aortas of SHR-HI. Notably, the use of the recoupling agent BH4 or a thiol-reducing agent blunted eNOS-dependent ROS production in the aortas of SHR-HI. In conclusion, the lack of a positive effect of high-intensity exercise on endothelial function in SHR was mainly explained by redox-dependent eNOS uncoupling, resulting in a switch from NO to O2(-) generation.

Monitoring changes in thioredoxin and over-oxidised peroxiredoxin in response to exercise in humans

Introduction. Peroxiredoxin (PRDX) and thioredoxin (TRX) are antioxidant proteins that control cellular signalling and redox balance, although their response to exercise is unknown. This study aimed to assess key aspects of the PRDX–TRX redox cycle in response to three different modes of exercise. Methods. Healthy males (n = 10, mean ± SD: 22 ± 3 yrs) undertook three exercise trials on separate days: two steady-state cycling trials at moderate (60% O2MAX; 27 min, MOD) and high (80% O2MAX; 20 min, HIGH) intensities, and a low-volume high-intensity interval training trial (10 × 1 min 90% O2MAX, LV-HIIT). Peripheral blood mononuclear cells were assessed for TRX-1 and over-oxidised PRDX (isoforms I–IV) protein expression before, during, and 30 min following exercise (post + 30). The activities of TRX reductase (TRX-R) and the nuclear factor kappa B (NF-κB) p65 subunit were also assessed. Results. TRX-1 increased during exercise in all trials (MOD, + 84.5%; HIGH, + 64.1%; LV-HIIT, + 205.7%; p < 05), whereas over-oxidised PRDX increased during HIGH only (MOD, − 28.7%; HIGH, + 202.9%; LV-HIIT, − 22.7%; p < .05). TRX-R and NF-κB p65 activity increased during exercise in all trials, with the greatest response in TRX-R activity seen in HIGH (p < 0.05). Discussion. All trials stimulated a transient increase in TRX-1 protein expression during exercise. Only HIGH induced a transient over-oxidation of PRDX, alongside the greatest change in TRX-R activity. Future studies are needed to clarify the significance of heightened peroxide exposure during continuous high-intensity exercise and the mechanisms of PRDX-regulatory control.

Application of the Speed-Duration Relationship to Normalize the Intensity of High-Intensity Interval Training

The tolerable duration of continuous high-intensity exercise is determined by the hyperbolic Speed-tolerable duration (S-tLIM) relationship. However, application of the S-tLIM relationship to normalize the intensity of High-Intensity Interval Training (HIIT) has yet to be considered, with this the aim of present study. Subjects completed a ramp-incremental test, and series of 4 constant-speed tests to determine the S-tLIM relationship. A sub-group of subjects (n = 8) then repeated 4 min bouts of exercise at the speeds predicted to induce intolerance at 4 min (WR4), 6 min (WR6) and 8 min (WR8), interspersed with bouts of 4 min recovery, to the point of exercise intolerance (fixed WR HIIT) on different days, with the aim of establishing the work rate that could be sustained for 960 s (i.e. 4×4 min). A sub-group of subjects (n = 6) also completed 4 bouts of exercise interspersed with 4 min recovery, with each bout continued to the point of exercise intolerance (maximal HIIT) to determine the appropriate protocol for maximizing the amount of high-intensity work that can be completed during 4×4 min HIIT. For fixed WR HIIT tLIM of HIIT sessions was 399±81 s for WR4, 892±181 s for WR6 and 1517±346 s for WR8, with total exercise durations all significantly different from each other (P<0.050). For maximal HIIT, there was no difference in tLIM of each of the 4 bouts (Bout 1: 229±27 s; Bout 2: 262±37 s; Bout 3: 235±49 s; Bout 4: 235±53 s; P>0.050). However, there was significantly less high-intensity work completed during bouts 2 (153.5±40. 9 m), 3 (136.9±38.9 m), and 4 (136.7±39.3 m), compared with bout 1 (264.9±58.7 m; P>0.050). These data establish that WR6 provides the appropriate work rate to normalize the intensity of HIIT between subjects. Maximal HIIT provides a protocol which allows the relative contribution of the work rate profile to physiological adaptations to be considered during alternative intensity-matched HIIT protocols.

Oxygen Uptake Kinetics: An Underappreciated Determinant of Exercise Performance

The rate at which VO(2) adjusts to the new energy demand following the onset of exercise strongly influences the magnitude of the "O(2) deficit" incurred and thus the extent to which muscle and systemic homeostasis is perturbed. Moreover, during continuous high-intensity exercise, there is a progressive loss of muscle contractile efficiency, which is reflected in a "slow component" increase in VO(2). The factors that dictate the characteristics of these fast and slow phases of the dynamic response of VO(2) following a step change in energy turnover remain obscure. However, it is clear that these features of the VO(2) kinetics have the potential to influence the rate of muscle fatigue development and, therefore, to affect sports performance. This commentary outlines the present state of knowledge on the characteristics of, and mechanistic bases to, the VO(2) response to exercise of different intensities. Several interventions have been reported to speed the early VO(2) kinetics and/or reduce the magnitude of the subsequent VO(2) slow component, and the possibility that these might enhance exercise performance is discussed.

Interval versus Continuous High-Intensity Exercise in Chronic Obstructive Pulmonary Disease: A Randomized Trial

Interval versus Continuous High-Intensity Exercise in Chronic Obstructive Pulmonary Disease: A Randomized Trial

INTERVAL VERSUS CONTINUOUS HIGH-INTENSITY EXERCISE IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Puhan MA, Busching G, Schunemann HJ, VanOort E, Zaugg C, Frey M Ann Intern Med. 2006;145:816-825. Background Guidelines recommend high-intensity continuous exercise to reduce peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease but acknowledge that interval exercise might be an equally effective alternative that is better tolerated by patients. Objective. To assess whether interval exercise is no less effective than high-intensity continuous exercise and whether it is tolerated better by patients with severe chronic obstructive pulmonary disease. Design. Randomized, noninferiority trial. Setting. Publicly funded rehabilitation hospital in Switzerland. Patients. 98 patients with severe chronic obstructive pulmonary disease, with or without recent exacerbations. Intervention. 12 to 15 supervised interval or high-intensity continuous exercise sessions (over 3 weeks) followed by exercise at home. Measurements. Health-related quality of life determined by using the Chronic Respiratory Questionnaire (CRQ) (scores from 1 [most severe impairment] to 7 [no impairment]) after 5 weeks and number of unintended breaks during supervised exercise. Results. Both groups experienced large improvements in health-related quality of life (increase of CRQ total scores of 1.00 [SD, 0.98] for the interval exercise group and 1.02 [SD, 1.05] for the continuous exercise group). Adjusted between-group differences between the interval exercise group and the continuous exercise group (−0.05 [95% CI, −0.42 to −0.32] for CRQ and 1.1 meters [CI, −25.4 to 27.6 meters] for 6-minute walking distance) were within the a priori defined boundaries of noninferiority (0.5 for CRQ and 45 meters for 6-minute walking distance). Twenty-one (47.9%) patients using interval exercise and 11 (24.0%) patients using continuous exercise were able to adhere to the protocol (difference, 23.9 percentage points [CI, 5.0 to 42.8 percentage points]; P = 0.014). The median number of unintended breaks lasting 1 minute or more was 2 (interquartile range, 0 to 16) for patients in the interval exercise group and 11 (interquartile range, 2 to 26) for patients in the continuous exercise group (P = 0.023). Limitations. The study focused on initiation of exercise and not on outpatient or home-based maintenance of exercise. Conclusions. Clinicians and patients can choose either of the 2 exercise plans to initiate physical exercise. Comment. The use of high-intensity exercise protocols in the initiation of pulmonary rehabilitation is well established. However, the more severely impaired patient often has difficulty with sustained exercise at the requisite workload levels (>70% of maximal exercise capacity), and this may directly affect not only the short-term outcome of exercise training but also the longer-term adherence to recommendations made during participation in pulmonary rehabilitation. This study is a well-designed randomized trial seeking to show that interval exercise (brief high-intensity bursts alternating with low-intensity exercise) is not inferior to high-intensity continuous exercise. Forty-nine and 51 patients were randomized to interval and continuous exercise groups, respectively; all had severe chronic obstructive pulmonary disease (mean FEV1, approximately 35% predicted, GOLD stage 3 and 4). At the end of 5 weeks (12 to 15 sessions), the interval group did not show less benefit in both health-related quality-of-life measures and 6-minute walk distance. Not only did the interval exercise group do at least as well using standard outcome measures, adherence to the assigned protocol was also significantly higher in this group, suggesting a higher level of patient preference. Whether the benefits would carry over into maintenance exercise training is unestablished, but the 2 protocols, interval and continuous exercise, seem to be equivalent in the initiation of pulmonary rehabilitation and can be offered as such, especially to patients with severe chronic obstructive pulmonary disease who may find the interval protocol more acceptable. SK

Interval versus Continuous High-Intensity Exercise in Chronic Obstructive Pulmonary Disease

Guidelines recommend high-intensity continuous exercise to reduce peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease but acknowledge that interval exercise might be an equally effective alternative that is better tolerated by patients. To assess whether interval exercise is no less effective than high-intensity continuous exercise and whether it is tolerated better by patients with severe chronic obstructive pulmonary disease. Randomized, noninferiority trial. Publicly funded rehabilitation hospital in Switzerland. 98 patients with severe chronic obstructive pulmonary disease, with or without recent exacerbations. 12 to 15 supervised interval or high-intensity continuous exercise sessions (over 3 weeks) followed by exercise at home. Health-related quality of life determined by using the Chronic Respiratory Questionnaire (CRQ) (scores from 1 [most severe impairment] to 7 [no impairment]) after 5 weeks and number of unintended breaks during supervised exercise. Both groups experienced large improvements in health-related quality of life (increase of CRQ total scores of 1.00 [SD, 0.98] for the interval exercise group and 1.02 [SD, 1.05] for the continuous exercise group). Adjusted between-group differences between the interval exercise group and the continuous exercise group (-0.05 [95% CI, -0.42 to -0.32] for CRQ and 1.1 meters [CI, -25.4 to 27.6 meters] for 6-minute walking distance) were within the a priori defined boundaries of noninferiority (0.5 for CRQ and 45 meters for 6-minute walking distance). Twenty-one (47.9%) patients using interval exercise and 11 (24.0%) patients using continuous exercise were able to adhere to the protocol (difference, 23.9 percentage points [CI, 5.0 to 42.8 percentage points]; P = 0.014). The median number of unintended breaks lasting 1 minute or more was 2 (interquartile range, 0 to 16) for patients in the interval exercise group and 11 (interquartile range, 2 to 26) for patients in the continuous exercise group (P = 0.023). The study focused on initiation of exercise and not on outpatient or home-based maintenance of exercise. Clinicians and patients can choose either of the 2 exercise plans to initiate physical exercise. International Standard Randomized Controlled Trial number: SRCTN11611768.

Interval versus Continuous High-Intensity Exercise for Patients with Chronic Obstructive Pulmonary Disease

Interval versus Continuous High-Intensity Exercise for Patients with Chronic Obstructive Pulmonary Disease

Interval exercise versus continuous exercise in patients with moderate to severe chronic obstructive pulmonary disease--study protocol for a randomised controlled trial [ISRCTN11611768

BackgroundPhysical exercise has become a cornerstone of management of chronic obstructive pulmonary disease (COPD) because it leads to clinically relevant improvements of exercise capacity and health-related quality of life (HRQL). Despite the scarcity of randomised trials directly comparing exercise protocols, current guidelines recommend high intensity continuous exercise for lower extremities as the probably most effective exercise modality. However, for patients admitted to inpatient respiratory rehabilitation programmes, it is often difficult to initiate such an exercise programme because they are severely limited by dyspnoea and leg fatigue and therefore unable to perform continuous exercise at higher intensities and for periods longer than 30 minutes. Interval exercise may be an attractive alternative for these COPD patients because it allows high intensity exercise with recovery periods. The aim of this study is to assess if interval exercise compared to high intensity continuous exercise is not of inferior effectiveness in terms of HRQL and exercise capacity improvements but associated with better exercise tolerance in patients with moderate to severe COPD at the beginning of a respiratory rehabilitation.Methods/DesignWe will assign patients with moderately severe to severe COPD to either continuous exercise or interval exercise using a stratified randomisation. Patients will follow 12–15 exercise sessions during a comprehensive inpatient respiratory rehabilitation. Primary end point for effectiveness is HRQL as measured by the Chronic Respiratory Questionnaire (CRQ) two weeks after the end of rehabilitation and secondary endpoints include additional clinical outcomes such as functional exercise capacity, other HRQL measures, patients' experience of physical exercise as well as physiological measures of the effects of physical exercise such as cardiopulmonary exercise testing. Including expected drop-outs, we will need 52 patients per group to show differences corresponding to the minimal clinically important difference of the CRQ. Outcome assessors and investigators involved in data analysis will be blinded to group assignment until analyses have been carried out.DiscussionClinicians and the scientific community need evidence on the benefits and tolerance of exercise protocols available in clinical practice. The proposed trial will provide important and needed data on interval and continuous exercise for decision making in clinical practice.