Breathing patterns during eccentric exercise

Cadence Modulation during Eccentric Cycling Affects Perception of Effort But Not Neuromuscular Alterations

INTRODUCTION

A recent study showed that cadence modulation during short eccentric cycling exercise affects oxygen consumption (V̇O 2 ), muscular activity (EMG), and perception of effort (PE). This study examined the effect of cadence on V̇O 2 , EMG, and PE during prolonged eccentric cycling and exercise-induced neuromuscular alterations.

METHODS

Twenty-two participants completed three sessions 2-3 wk apart: 1) determination of the maximal concentric peak power output, familiarization with eccentric cycling at two cadences (30 and 60 rpm at 60% peak power output), and neuromuscular testing procedure; 2) and 3) 30 min of eccentric cycling exercise at a cadence of 30 or 60 rpm. PE, cardiorespiratory parameters, and vastus lateralis and rectus femoris EMG were collected during exercise. The knee extensors' maximal voluntary contraction torque, the torque evoked by double stimulations at 100 Hz (Dt100) and 10 Hz (Dt10), and the voluntary activation level were evaluated before and after exercise.

RESULTS

V̇O 2 , EMG, and PE were greater at 30 than 60 rpm (all P < 0.05). Maximal voluntary contraction torque, evoked torque, and Dt10/Dt100 ratio decreased (all P < 0.01) without cadence effect (all P > 0.28). Voluntary activation level remained constant after both eccentric cycling exercises ( P = 0.87).

CONCLUSIONS

When performed at the same power output, eccentric cycling exercise at 30 rpm elicited a greater PE, EMG, and cardiorespiratory demands than pedaling at 60 rpm. Exercise-induced fatigability was similar in both eccentric cycling conditions without neural impairments, suggesting that eccentric cycling seemed to alter more specifically muscular function, such as the excitation-contraction coupling process. In a rehabilitation context, eccentric cycling at 60 rpm seems more appropriate because it will induce lower PE for similar strength loss compared with 30 rpm.

Acute physiological responses to eccentric cycling: a systematic review and meta-analysis

INTRODUCTION

Eccentric cycling (ECCCYC) has attracted considerable interest due to its potential applicability for exercise treatment/training of patients with poor exercise tolerance as well as healthy and trained individuals. Conversely, little is known about the acute physiological responses to this exercise modality, thus challenging its proper prescription. This study aimed to provide precise estimates of the acute physiological responses to ECCCYC in comparison to traditional concentric cycling (CONCYC).

EVIDENCE ACQUISITION

Searches were performed until November 2021 using the PubMed, Embase, and ScienceDirect databases. Studies that examined individuals' cardiorespiratory, metabolic, and perceptual responses to ECCCYC and CONCYC sessions were included. Bayesian multilevel meta-analysis models were used to estimate the population mean difference between acute physiological responses from ECCCYC and CONCYC bouts. Twenty-one studies were included in this review.

EVIDENCE SYNTHESIS

The meta-analyses showed that ECCCYC induced lower cardiorespiratory (i.e., V̇O2, V̇E, and HR), metabolic (i.e., [BLa]), and perceptual (i.e., RPE) responses than CONCYC performed at the same absolute power output, while greater cardiovascular strain (i.e., greater increases in HR, Q, MAP, [norepinephrine], and lower SV) was detected when compared to CONCYC performed at the same V̇O2.

CONCLUSIONS

The prescription of ECCCYC based on workloads used in the CONCYC sessions may be considered safe and, therefore, feasible for the rehabilitation of individuals with poor exercise tolerance. However, the prescription of ECCCYC based on the V̇O2 obtained during CONCYC sessions should be conducted with caution, especially in clinical settings, since there is a high probability of additional cardiovascular overload in this condition.

Effect of Cadence on Physiological and Perceptual Responses during Eccentric Cycling at Different Power Outputs

INTRODUCTION

The effect of cadence in eccentric (ECC) cycling on physiological and perceptual responses is, to date, poorly understood. This study aimed to evaluate the effect of cadence during ECC cycling on muscular activation (EMG), oxygen consumption (V̇O 2 ), and perceived effort (PE) for two different levels of power output.

METHODS

Seventeen participants completed four sessions 1 wk apart: 1) determination of the maximal concentric peak power output (PPO) and familiarization with ECC cycling at five cadences (30, 45, 60, 75, and 90 rpm); 2) second familiarization with ECC cycling; 3) and 4) ECC cycling exercise consisting of 5 min at the five different cadences at either 40% or 60% PPO. PE was reported, and V̇O 2 and EMG of seven muscles were calculated over the exercise's last minute.

RESULTS

PE, V̇O 2 , and global lower limb muscles activation (EMG ALL ) showed an effect of cadence ( P < 0.001) and followed a curvilinear function. Both low and high cadences increased PE and V̇O 2 responses compared with intermediate cadences. Although muscle activation of vastus lateralis follows a U-shaped curve with cadence, it was greater at low cadence for rectus femoris and biceps femoris, greater at high cadence for tibialis anterior and gastrocnemius medialis, and was not altered for soleus. The estimated optimal cadence was greater (all P < 0.01) for V̇O 2 (64.5 ± 7.9 rpm) than PE (61.7 ± 9.4 rpm) and EMG ALL (55.9 ± 9.3 rpm), but power output had no effect on the optimal cadences.

CONCLUSIONS

The physiological and perceptual responses to changes in cadence during ECC cycling followed a U-shaped curve with an optimal cadence depending on the parameter considered.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Eccentric Training in Pulmonary Rehabilitation of Post-COVID-19 Patients: An Alternative for Improving the Functional Capacity, Inflammation, and Oxidative Stress

The purpose of this narrative review is to highlight the oxidative stress induced in COVID-19 patients (SARS-CoV-2 infection), describe longstanding functional impairments, and provide the pathophysiologic rationale that supports aerobic eccentric (ECC) exercise as a novel alternative to conventional concentric (CONC) exercise for post-COVID-19 patients. Patients who recovered from moderate-to-severe COVID-19 respiratory distress demonstrate long-term functional impairment. During the acute phase, SARS-CoV-2 induces the generation of reactive oxygen species that can be amplified to a "cytokine storm". The resultant inflammatory and oxidative stress process causes organ damage, particularly in the respiratory system, with the lungs as the tissues most susceptible to injury. The acute illness often requires a long-term hospital stay and consequent sarcopenia. Upon discharge, muscle weakness compounded by limited lung and cardiac function is often accompanied by dyspnea, myalgia, anxiety, depression, and sleep disturbance. Consequently, these patients could benefit from pulmonary rehabilitation (PR), with exercise as a critical intervention (including sessions of strength and endurance or aerobic exercises). Unfortunately, conventional CONC exercises induce significant cardiopulmonary stress and increase inflammatory and oxidative stress (OS) when performed at moderate/high intensity, which can exacerbate debilitating dyspnoea and muscle fatigue post-COVID-19. Eccentric training (ECC) is a well-tolerated alternative that improves muscle mass while mitigating cardiopulmonary stress in patients with COPD and other chronic diseases. Similar benefits could be realized in post-COVID-19 patients. Consequently, these patients could benefit from PR with exercise as a critical intervention.

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling

Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18–51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5–0.75) to good (ICC = 0.75–0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70–0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ214 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

Concentric not eccentric cycling sprint intervals acutely impair balance and jump performance in healthy active young adults: A randomized controlled cross-over study

INTRODUCTION

Moderate aerobic, high-intensity and sprint running or cycling training can transiently impair postural control. However, the acute effects of modified sprint interval training (mSIT) at different muscle working modes have not yet been examined. Thus, this study aimed at investigating acute effects of time-matched eccentric (ECC) versus concentric mSIT cycling session (CON) on jumping and functional balance performance.

METHODS

Twenty-five healthy and active males (30.0 ± 6.0 years; 80.1 ± 9.1 kg; V̇O_2max: 64.2 ± 7.9 mL kg^-1 min^-1) were enrolled in this acute randomized controlled crossover trial. Counter-Movement-Jump (CMJ) and functional balance testing (Y-Balance-Test composite score [YBT_CS]; Posturomed total distance: Posturomed_TD) were assessed as primary outcomes before, and immediately after cessation of ECC and CON (10 × 10 s maximum sprints and 50 s of active recovery).

RESULTS

A significant mode × time interaction effect for CMJ (F = 9.620, p = 0.005, η_p² = 0.29) was observed. Subsequent post-hoc testing revealed significant moderate reductions in jumping height after CON (0.31 ± 0.06 vs. 0.27 ± 0.06m; p = 0.004, SMD = 0.59), whilst ECC remained unchanged. YBT_CS (mode × time interaction: F = 6.880, p = 0.015, η_p² = 0.22) showed small but significant balance impairments after CON (0.964 ± 0.068 vs. 0.960 ± 0.063 AU; p = 0.009, SMD = 0.28) and did not significantly change after ECC. Although large significant interaction effects (p = 0.029, η_p² = 0.18) were observed for Posturomed_TD, follow up post-hoc testing did not reveal relevant pre-post differences, neither for ECC nor CON.

CONCLUSION

Both functional balance and jumping performance are deteriorated after acute concentric but not eccentric mSIT cycling. Although higher pedal forces at lower perceived efforts and heart rates during eccentric mSIT were observed, it seems that the cardiocirculatory demanding CON session elicited more pronounced balance and jump performance impairments than eccentric cycling.

Concentric versus eccentric cycling at equal power output or effort perception: Neuromuscular alterations and muscle pain

This study aimed to compare neuromuscular alterations and perceptions of effort and muscle pain induced by concentric and eccentric cycling performed at the same power output or effort perception. Fifteen participants completed three 30-min sessions: one in concentric at 60% peak power output (CON) and two in eccentric, at the same power output (ECC_POWER ) or same perceived effort (ECC_EFFORT ). Muscle pain, perception of effort, oxygen uptake as well as rectus femoris and vastus lateralis electromyographic activities were collected when pedaling. The knee extensors maximal voluntary contraction (MVC) torque, the torque evoked by double stimulations at 100 Hz and 10 Hz (Dt100; Dt10), and the voluntary activation level (VAL) were evaluated before and after exercise. Power output was higher in ECC_EFFORT than CON (89.1 ± 23.3% peak power). Muscle pain and effort perception were greater in CON than ECC_POWER (p < 0.03) while muscle pain was similar in CON and ECC_EFFORT (p > 0.43). MVC torque, Dt100, and VAL dropped in all conditions (p < 0.04). MVC torque (p < 0.001) and the Dt10/ Dt100 ratio declined further in ECC_EFFORT (p < 0.001). Eccentric cycling perceived as difficult as concentric cycling caused similar muscle pain but more MVC torque decrease. A given power output induced lower perceptions of pain and effort in eccentric than in concentric yet similar MVC torque decline. While neural impairments were similar in all conditions, eccentric cycling seemed to alter excitation-contraction coupling. Clinicians should thus be cautious when setting eccentric cycling intensity based on effort perception.

Ventilatory adaptation during eccentric cycling in patients with severe COPD: Potential implications for exercise training

INTRODUCTION

Eccentric (ECC) cycling is viewed as an alternative to concentric (CON) cycling for exercise training in patients with severe COPD as it induces a much lower ventilatory demand for a given mechanical load than CON cycling. However, a more hyperpneic breathing pattern (i.e., higher f_B and lower tidal volume (VT)) during ECC than during CON has been reported in healthy subjects.

RESEARCH QUESTION

Do patients with severe COPD develop a more hyperpneic breathing pattern during ECC than during CON cycling, and is it associated with differences in dynamic hyperinflation, ventilatory efficiency and cardiometabolic adaptation?

METHODS

Fourteen patients with severe COPD performed incremental CON and ECC cardiopulmonary exercise tests (CPET). Several physiological parameters including VT, f_B, inspiratory capacity (IC) and oxygen consumption (V̇O₂) were recorded at each workload increment during CPET.

RESULTS

At the highest identical minute ventilation (V̇E) achieved during ECC and CON (28.6 ± 4.6 L.min^-1), VT was lower (1010 ± 218 vs. 1100 ± 233 mL; p = 0.02), f_B was higher (29.0 ± 5.1 vs. 27.0 ± 5.5 min^-1; p = 0.03), IC(% baseline) was lower (84 ± 10 vs. 78 ± 9; p < 0.01) and markers of ventilatory efficiency were poorer during ECC than during CON. Similar results were found at the highest identical V̇O₂ achieved during ECC and CON.

CONCLUSION

The finding of a more hyperpneic ventilatory pattern during ECC cycling together with a lower IC and a poorer ventilatory efficiency suggests that ECC exercise training should be decided with caution in patients with severe COPD.

Aerobic Metabolic Adaptations in Endurance Eccentric Exercise and Training: From Whole Body to Mitochondria

A characteristic feature of eccentric as compared with concentric exercise is the ability to generate greater mechanical loads for lower cardiopulmonary demands. Current evidence concurs to show that eccentric training translates into considerable gains in muscle mass and strength. Less is known, however, regarding its impact on oxygen transport and on factors to be considered for optimizing its prescription and monitoring. This article reviews the existing evidence for endurance eccentric exercise effects on the components of the oxygen transport system from systemic to mitochondria in both humans and animals. In the studies reviewed, specially designed cycle-ergometers or downhill treadmill running were used to generate eccentric contractions. Observations to date indicate that overall, the aerobic demand associated with the eccentric training load was too low to significantly increase peak maximal oxygen consumption. By extension, it can be inferred that the very high eccentric power output that would have been required to solicit a metabolic demand sufficient to enhance peak aerobic power could not be tolerated or sustained by participants. The impact of endurance eccentric training on peripheral flow distribution remains largely undocumented. Given the high damage susceptibility of eccentric exercise, the extent to which skeletal muscle oxygen utilization adaptations would be seen depends on the balance of adverse and positive signals on mitochondrial integrity. The article examines the protection provided by repeated bouts of acute eccentric exercise and reports on the impact of eccentric cycling and downhill running training programs on markers of mitochondrial function and of mitochondrial biogenesis using mostly from animal studies. The summary of findings does not reveal an impact of training on skeletal muscle mitochondrial respiration nor on selected mitochondrial messenger RNA transcripts. The implications of observations to date are discussed within future perspectives for advancing research on endurance eccentric exercise physiological impacts and using a combined eccentric and concentric exercise approach to optimize functional capacity.

Moving forward with backward pedaling: a review on eccentric cycling

PURPOSE

There is a profound gap in the understanding of the eccentric cycling intensity continuum, which prevents accurate exercise prescription based on desired physiological responses. This may underestimate the applicability of eccentric cycling for different training purposes. Thus, we aimed to summarize recent research findings and screen for possible new approaches in the prescription and investigation of eccentric cycling.

METHOD

A search for the most relevant and state-of-the-art literature on eccentric cycling was conducted on the PubMed database. Literature from reference lists was also included when relevant.

RESULTS

Transversal studies present comparisons between physiological responses to eccentric and concentric cycling, performed at the same absolute power output or metabolic load. Longitudinal studies evaluate responses to eccentric cycling training by comparing them with concentric cycling and resistance training outcomes. Only one study investigated maximal eccentric cycling capacity and there are no investigations on physiological thresholds and/or exercise intensity domains during eccentric cycling. No study investigated different protocols of eccentric cycling training and the chronic effects of different load configurations.

CONCLUSION

Describing physiological responses to eccentric cycling based on its maximal exercise capacity may be a better way to understand it. The available evidence indicates that clinical populations may benefit from improvements in aerobic power/capacity, exercise tolerance, strength and muscle mass, while healthy and trained individuals may require different eccentric cycling training approaches to benefit from similar improvements. There is limited evidence regarding the mechanisms of acute physiological and chronic adaptive responses to eccentric cycling.

Leg Muscle Activity and Perception of Effort before and after Four Short Sessions of Submaximal Eccentric Cycling

Background: This study tested muscle activity (EMG) and perception of effort in eccentric (ECC) and concentric (CON) cycling before and after four sessions of both. Methods: Twelve volunteers naïve to ECC cycling attended the laboratory six times. On day 1, they performed a CON cycling peak power output (PPO) test. They then carried-out four sessions comprising two sets of 1 to 1.5-min cycling bouts at 5 intensities (30, 45, 60, 75, and 90% PPO) in ECC and CON cycling. On day 2 and day 6 (two weeks apart), EMG root mean square of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and soleus (SOL) muscles, was averaged from 15 to 30 s within each 1-min bout and perception of effort was asked after 45 s. Results: Before the four cycling sessions, while VL EMG was lower in ECC than CON cycling, most variables were not different. Afterwards, ECC cycling exhibited lower RF EMG at 75 and 90% PPO (all p < 0.02), lower VL and BF EMG at all exercise intensities (all p < 0.02), and inferior SOL EMG (all p < 0.04) except at 45% PPO (p = 0.07). Perception of effort was lower in ECC cycling at all exercise intensities (all p < 0.03) but 60% PPO (p = 0.11). Conclusions: After four short sessions of ECC cycling, the activity of four leg muscles and perception of effort became lower in ECC than in CON cycling at most of five power outputs, while they were similar before.

Neuromuscular and Perceptual Responses to Sub-Maximal Eccentric Cycling

Objective

Eccentric (ECC) cycle-ergometers have recently become commercially-available, offering a novel method for rehabilitation training. Many studies have reported that ECC cycling enables the development of higher levels of muscular force at lower cardiorespiratory and metabolic loads, leading to greater force enhancements after a training period. However, fewer studies have focused on the specific perceptual and neuromuscular changes. As the two latter aspects are of major interest in clinical settings, this review aimed to present an overview of the current literature centered on the neuromuscular and perceptual responses to submaximal ECC cycling in comparison to concentric (CON) cycling.

Design

Narrative review of the literature.

Results

At a given mechanical workload, muscle activation is lower in ECC than in CON while the characteristics of the musculo-articular system (i.e., muscle-tendon unit, fascicle, and tendinous tissue length) are quite similar. At a given heart rate or oxygen consumption, ECC cycling training results in greater muscular hypertrophy and strength gains than CON cycling. On the contrary, CON cycling training seems to enhance more markers of muscle aerobic metabolism than ECC cycling performed at the same heart rate intensity. Data concerning perceptual responses, and neuromuscular mechanisms leading to a lower muscle activation (i.e., neural commands from cortex to muscular system) at a given mechanical workload are scarce.

Conclusion

Even though ECC cycling appears to be a very useful tool for rehabilitation purposes the perceptual and neural commands from cortex to muscular system during exercise need to be further studied.

Faster oxygen uptake, heart rate, and ventilatory kinetics in stepping compared with cycle ergometry in patients with COPD during moderate-intensity exercise

Step tests are a stressful and feasible cost-effective modality to evaluate aerobic performance. However, the eccentric in addition to concentric muscle contractions of the legs on stepping emerge as a potential speeding factor for cardioventilatory and metabolic adjustments towards a steady-state, since eccentric contractions would prompt an earlier and stronger mechanoreceptor activation, as well as higher heart rate/cardiac output adjustments to the same metabolic demand. Moreover, shorter tests are ideal for exercise-limited subjects. Nine subjects with chronic obstructive pulmonary disease were invited to participate in comprehensive lung function tests and constant work tests performed on different days at a 90% gas exchange threshold for 6 min, in single-step tests or cycle ergometry. After careful monoexponential regression modelling, statistically relevant faster phase II time constants for oxygen uptake (45 ± 18 s vs 53 ± 17 s, p = 0.017) and minute ventilation (61 ± 13 s vs 74 ± 17 s, p = 0.027) were observed in the 6-min step tests compared with cycle ergometry, respectively. Despite an absence of heart rate time constant difference (43 ± 20 s vs 69 ± 46 s, p = 0.167), there was a significantly faster rate constant toward a steady state for heart rate (p = 0.02). In addition, 4-min compared with 6-min analysis presented similar results (p > 0.05), providing an appropriate steady-state. We conclude that step tests might elicit faster time constants compared with cycle ergometry, at the same average metabolic level, and 4-min analysis has similar mean errors compared with 6-min analysis within an acceptable range. New studies, comprising mechanisms and detailed physiological backgrounds, are necessary.

Cardiorespiratory Responses to Downhill Versus Uphill Running in Endurance Athletes

PURPOSE

Mountain running races are becoming increasingly popular, although our understanding of the particular physiology associated with downhill running (DR) in trained athletes remains scarce. This study explored the cardiorespiratory responses to high-slope constant velocity uphill running (UR) and DR.

METHOD

Eight endurance athletes performed a maximal incremental test and 2 15-min running bouts (UR, +15%, or DR, -15%) at the same running velocity (8.5 ± 0.4 km·h^-1). Oxygen uptake ([Formula: see text]O₂), heart rate (HR), and ventilation rates ([Formula: see text]_E) were continuously recorded, and blood lactate (bLa) was measured before and after each trial.

RESULTS

Downhill running induced a more superficial [Formula: see text]_E pattern featuring reduced tidal volume (p < .05, ES = 6.05) but similar respiratory frequency (p > .05, ES = 0.68) despite lower [Formula: see text]_E (p < .05, ES = 5.46), [Formula: see text]O₂ (p < .05, ES = 12.68), HR (p < .05, ES = 6.42), and bLa (p < .05, ES = 1.70). A negative slow component was observed during DR for [Formula: see text]O₂ (p < .05, ES = 1.72) and HR (p < .05, ES = 0.80).

CONCLUSIONS

These results emphasize the cardiorespiratory responses to DR and highlight the need for cautious interpretation of [Formula: see text]O₂, HR, and [Formula: see text]_E patterns as markers of exercise intensity for training load prescription and management.

Oxygen consumption, rate of perceived exertion and enjoyment in high-intensity interval eccentric cycling

The objectives of this article are to compare oxygen consumption (VO₂) and perceptual responses between continuous and interval eccentric cycling protocols in order to test the hypothesis that metabolic demand and enjoyment would be greater for interval than continuous eccentric cycling protocols. Eleven recreationally active men (n = 9) and women (32.6 ± 9.4 years) performed a concentric cycling test to determine peak power output (PPO) followed by five eccentric cycling protocols on separate occasions: continuous eccentric cycling at 60% of PPO for 20 min at 60 rpm (CONT_20@60%) and 13.2 min at 90 rpm (CONT_13@60%), 4 × 4 min at 75% of PPO with 2-min rest (INT_4×4@75%), 12 × 1 min at 100% of PPO with 1-min rest (INT_1×12@100%) and 10 × 1 min at 150% of PPO with 1-min rest (INT_1×10@150%). Gas exchange and power output were recorded continuously, and rate of perceived exertion (RPE) and enjoyment were assessed after each exercise. Total VO₂ including the rest periods was the greatest (p < 0.0001) during INT_1×10@150% (382 ± 73 ml kg^-1) and lowest (p < 0.0001) during CONT_13@60% (146 ± 27 ml kg^-1). Total VO₂ during INT_1×12@100% (312 ± 59 ml kg^-1) was greater (p < 0.0001) than CONT_20@60% (246 ± 63 ml kg^-1) and INT_4×4@75% (257 ± 42 ml kg^-1). RPE was greater (p < 0.0001) after INT_1×10@150% (17 ± 2) than other conditions, but perceived enjoyment was not significantly different between protocols. It was concluded that the interval protocols increased metabolic demand without increasing RPE and enjoyment. It appears that high-intensity interval protocols can be used in eccentric cycling prescription.