Feeling of Pleasure to High-Intensity Interval Exercise Is Dependent of the Number of Work Bouts and Physical Activity Status

Reduced-exertion high-intensity interval training (REHIT): a feasible approach for improving health and fitness?

In recent years, research investigating the dose-response to sprint interval training (SIT) has provided evidence that the number and duration of repetitions in a SIT session can be reduced whilst preserving the beneficial health-related adaptations. Together this research has led to the development of protocols involving minimal doses of SIT: regularly performing just two or three 20-30 s all-out sprints in a 10 min training session has been shown to elicit beneficial metabolic and cardiovascular adaptations. These SIT protocols, which we originally termed "reduced-exertion high-intensity interval training" (or REHIT), have the potential to remove many of the common barriers associated with other SIT protocols, as well as with HIT and aerobic exercise. Here, we critically review the evidence on the efficacy, feasibility and acceptability, and effectiveness of REHIT for improving health and fitness.

Effect of High-Intensity Interval, Moderate-Intensity Continuous, and Self-Selected Intensity Training on Health and Affective Responses

Purpose: To compare the effects of 12-week high-intensity interval (HIIT), moderate-intensity continuous (MICT), and self-selected intensity training (SSIT) on health outcomes and affective responses. Methods: Seventy-three overweight/obese inactive adults (62% woman; age, 31.4 ± 7.2 years; height, 1.66 ± 0.09 cm; Body mass index, 28.9 ± 2.7 kg.m-2) who were randomized into HIIT (n = 23), MICT (n = 24) and SSIT (n = 26) groups. The training was conducted three times per week in an outdoor environment, with 4 weeks under direct supervision and 8 weeks with semi-supervision. Cardiorespiratory fitness, body composition, and metabolic profile were evaluated at baseline and at the end of the 4th and 12th weeks. Core affect was measured during all training sessions. Results: Peak oxygen uptake improved in all groups after 4 and 12 weeks compared with baseline. Only the SSIT had reductions in body fat throughout the intervention. No improvements were observed in the metabolic profile across all groups. SSIT was perceived as more pleasurable than HIIT; however, there were no differences in affective responses between SSIT and MICT. Affective responses in-task (e.g. negative and positive peak, rate of change and affect at the end of the exercise session) predicted the HIIT and SSIT exercises attendance rate. Conclusion: Regardless of the exercise training protocol, overweight/obese inactive adults improved health outcomes, which suggests the prescribing HIIT, MICT, and SSIT in outdoor environments. SSIT should be considered in order to optimize the pleasure during training sessions. Affective response more positive in-task of the HIIT and SSIT is associated with greater attendance rate in these exercise protocols.

Shorter Versus Longer Durations of Rowing-Based Interval Exercise Attenuate the Physiological and Perceptual Response

Purpose: This study compared physiological and perceptual variables between short and long durations of rowing-based high intensity interval exercise (HIIE). Methods: Fourteen active adults (age = 26.4 ± 7.2 yr) performed incremental rowing exercise to fatigue to measure maximal oxygen uptake (VO2max) and peak power output (PPO). The subsequent 20 min sessions required HIIE (eight 60 s efforts at 85%PPO with 90 s of active recovery at 20%PPO or 24 20 s efforts at 85%PPO with 30 s of active recovery at 20%PPO) or moderate intensity continuous exercise (MICE) at 40%PPO. During exercise, VO2, heart rate (HR), blood lactate concentration (BLa), rating of perceived exertion (RPE), and affective valence were measured. Results: Data show significantly (p < 0.001) higher peak VO2 (84 ± 7 vs. 76 ± 5%VO2peak, d = 0.99), peak HR (94 ± 4%HRpeak vs. 90 ± 4%HRpeak, d = 1.12), BLa (7.0 ± 2.5 mM vs. 4.1 ± 1.0 mM, d = 1.22), end-exercise RPE (12.8 ± 2.0 vs. 11.0 ± 1.7, d = 1.29), and lower affective valence (2.1 ± 1.6 vs. 2.9 ± 1.2, d = 0.61) with long versus short HIIE. Time spent above 85%HRpeak was significantly higher (p < 0.001) in short versus long HIIE (606 ± 259 vs. 448 ± 26 s, d = 0.91). Conclusion: Longer rowing-based intervals elicit greater cardiometabolic and perceptual strain versus shorter efforts, making the latter preferable to optimize perceptual responses to HIIE.

The Feeling of Pleasure for Overweight Children during Different Types of Physical Activity

The feeling of pleasure during physical education (PE) could increase with physical activity participation and adherence for overweight children. While traditional games are known to have positive benefits on motor skill development, especially for children with poorer motor skills, and on the body mass of children, little is known about overweight children's feelings of enjoyment when playing these games. To identify a program of physical activity appreciated by overweight children, we tested the effect of different activities, namely soccer (SO), shot put (SP), and traditional motor games (TMGs), on the feelings of pleasure for 28 overweight male children (aged 12.11 ± 0.63 years, BMI 26.89 ± 0.15 kg·m-2) participating in a 3-month cross-over study. To measure affective responses to exercises, we applied a validated feeling scale. The data were collected during eight PE lessons, which were organized for each cycle taught. Post hoc pairwise comparisons revealed a significant difference (Z = -3.195, p < 0.01) between the mean feeling score reported after the SO cycle (2.48 ± 0.41) and that after the TMGs (3.04 ± 0.32). A similar significant difference (Z = -3.304, p < 0.01) was found between the mean feeling scores reported after the SP cycle (2.27 ± 0.32) and the TMGs (3.04 ± 0.32). There was no significant difference between the mean feeling scores reported after the SO (2.48 ± 0.41) and SP cycles (2.27 ± 0.32). In conclusion, the findings of the present study suggest that TMGs may have beneficial effects on the feelings of pleasure for overweight children. Therefore, TMGs might potentially be considered as an alternative to conventional physical activities.

Training effects of set- and repetition-interval rest time on recumbent-boxing exercise: Could virtual reality improve further?

This study examined the influence of set-interval and repetition-interval rest time of virtual reality (VR) boxing game in supine-lying posture. Fifty healthy middle-aged adults were randomly assigned into VR and non-VR groups to perform six different exercise protocols with varying set-interval and repetition-interval rest times (S0R0, S0R1/3, S0R2/3, S40R0, S40R1/3, and S40R2/3). Analysis on the non-VR group showed significant differences between exercise protocols for average heart rate (p < 0.001), maximum ventilation volume (p < 0.001), respiratory quotient (p < 0.001), oxygen pulse (p < 0.001), and excess post-exercise oxygen consumption (EPOC) (p = 0.003). VR appeared to have no further improvement on physical training effects in middle-aged adults, while the participants reported negative experience that might be associated with the over-exertion. Future study might need to explore game design elements that can accommodate high-exertion exercises.

Little but Intense: Using a HIIT-Based Strategy to Improve Mood and Cognitive Functioning in College Students

Looking for useful and motivational strategies for promoting healthy habits and improving cognitive functioning in young populations, the aim of the present study was to determine if a single bout of high-intensity interval exercise could stimulate mood and working memory in college students. A total of 25 male subjects (mean ± SD, age: 21.7 ± 2.1 years; height: 1.77 ± 0.06 m; weight: 72.6 ± 8.4 kg; body mass index: 23.1 ± 1.4 kg/m²; VO_2peak: 47.1 ± 9.3 mL/kg/min) participated voluntarily in this study. Participants underwent a high-intensity interval exercise consisting of 10 × 1 min of cycling at VO_2peak power output. The Profile of Mood States (POMS) questionnaire and Digit Span Test (DST) were administered at three assessment time points: (a) pre-intervention assessment, (b) post-intervention assessment, and (c) 30 min post-intervention. The mood states decreased significantly after exercise; however, a significant increase in mood was found after 30 min of recovery. A significant post-exercise increase in DST performance was observed; moreover, DST scores obtained 30 min after exercise remained higher than those assessed pre-exercise. In conclusion, a single bout of HIIT induces acute positive changes in mood states in male college students and seems to be a powerful stimulus for cognitive functioning.

Chronic Effects of Different Intensities of Interval Training on Hemodynamic, Autonomic and Cardiorespiratory Variables of Physically Active Elderly People

Interval training (IT) is a very efficient method. We aimed to verify the chronic effects of IT with different intensities on hemodynamic, autonomic and cardiorespiratory variables in the elderly. Twenty-four physically active elderly men participated in the study and were randomized into three groups: Training Group A (TG_A, n = 8), Training Group B (TG_B, n = 8) and control group (CG, n = 8). The TG_A and TG_B groups performed 32 sessions (48 h interval). TG_A presented 4 min (55 to 60% of HRmax) and 1 min (70 to 75% of HRmax). The TGB training groups performed the same protocol, but performed 4 min at 45 to 50% HRmax and 1 min at 60 to 65% HRmax. Both training groups performed each set six times, totaling 30 min per session. Assessments were performed pre (baseline) after the 16th and 32nd intervention session. The CG performed only assessments. Hemodynamic, autonomic and cardiorespiratory (estimated VO_2max) variables were evaluated. There were no significant differences between protocols and times (p > 0.05). However, the effect size and percentage delta indicated positive clinical outcomes, indicating favorable responses of IT. IT may be a strategy to improve hemodynamic, autonomic and cardiorespiratory behavior in healthy elderly people.

Is There a Dose-Response Relationship between High-Intensity Interval Exercise (HIIE) Intensity and Affective Valence? Analysis of Three HIIE Sessions Performed with Different Amplitudes

The inverse relationship between exercise intensity and affective valence is well established for continuous exercise but not for high-intensity interval exercise (HIIE). The objective was to verify the dose-response relationship between exercise intensity and affective valence in HIIE sessions. Eleven young men underwent a vigorous-intensity continuous exercise (VICE) and three HIIE sessions at the same average intensity (70% of peak power-W_Peak) and duration (20 min) but with different amplitudes: 10 × [1 min at 90% W_Peak/1 min at 50% W_Peak]-HIIE-90/50; 10 × [1 min at 100% W_Peak/1 min at 40% W_Peak]-HIIE-100/40; 10 × [1 min at 110% W_Peak/1 min at 30% W_Peak]-HIIE-110/30. During the exercise sessions, psychophysiological variables were recorded (VO₂, VCO₂, heart rate, perceived exertion CR10, and Feeling Scale (FS)). Higher correlations were found between CR10 and FS for all conditions (VICE = -0.987; HIIE-90/50 = -0.873; HIIE-100/40 = -0.908; HIIE-110/30 = -0.948). Regarding the physiological variables, the %HR_Max presented moderate inverse correlations with FS for all exercise conditions (VICE = -0.867; HIIE-90/50 = -0.818; HIIE-100/40 = -0.837; HIIE-110/30 = -0.828) while the respiratory variables (%VO_2Peak and %VCO_2Peak) presented low-to-moderate correlations only for VICE, HIIE-90/50, and HIIE-100/40 (ranging from -0.523 to -0.805). Poor correlations were observed between the %VO_2Peak (r = -0.293) and %VCO_2Peak (r = -0.020) with FS. The results indicated that perceived exertion is more sensible than physiological variables to explain the intensity-affective valence relationship in HIIE sessions. RPE should be used for HIIE prescription with a focus on affect.

The effects of low-volume combined training on health-related physical fitness outcomes in active young adults. A controlled clinical trial

The effects of combined training (CT) on improving general health are well known, however, few studies have investigated the effects of low-volume CT. So, the aim of this study is to investigate the effects of 6 weeks of low-volume CT on body composition, handgrip strength (HGS), cardiorespiratory fitness (CRF) and affective response (AR) to exercise. Eighteen healthy, active young adult man (mean ​± ​SD, [20.06 ± 1.66] years; [22.23 ± 2.76] ​kg/m²) performed either a low-volume CT (EG, n ​= ​9), or maintained a normal life (CG, n ​= ​9). The CT was composed of three resistance exercises followed by a high intensity-interval training (HIIT) on cycle ergometer performed twice a week. The measures of the body composition, HGS, maximal oxygen consumption ( V ˙ O_2max) and AR to exercise were taken at baseline and after training for analysis. Furthermore, an ANOVA test of repeated measures and t-test paired samples were used with a p ​≤ ​0.05. The results showed that EG improved HGS (pre: [45.67 ± 11.84] ​kg vs. post: [52.44 ± 11.90] ​kg, p ​< ​0.01) and V ˙ O_2max (pre: [41.36 ± 5.16] ​ml⋅kg^-1⋅min^-1 vs. post: [44.07 ± 5.98] ​ml⋅kg^-1⋅min^-1, p ​< ​0.01). Although, for all measures the body composition had not significant differences between weeks (p ​> ​0.05), nevertheless the feeling scale was positive in all weeks and without significant differences between them (p ​> ​0.05). Lastly, for active young adults, the low-volume CT improved HGS, CRF and had a positive outcome in AR, with less volume and time spent than traditional exercise recommendations.

Psychophysiological Responses of Exercise Distribution During High Intensity Interval Training Using Whole Body Exercise

The time-efficient nature of HIIT using bodyweight exercises can facilitate the application of exercise programs at home by encouraging more people to perform regular physical exercise. However, there are no studies investigating the influence of the distribution/order of exercises during HIIT training sessions using this method. The aim of the present study was to evaluate the effects of different exercise orders on training load indicators during HIIT sessions using body weight. Twenty male participants performed three 20-min sessions of HIIT using whole body exercise, consisting of 20 sets with 30 s of activity performed at maximal intensity, followed by 30 s of passive recovery. Three designs of exercise protocols were randomly performed according to the following exercise distribution: A: jumping jack, burpee, mountain climb and squat jump); B: jumping jack, mountain climb, burpee, and squat jump) and C: burpee, squat jump, jumping jack and mountain climb. No differences were found between protocols for relative heart rate, perceived exertion, and lactate concentrations. Significant differences (p &lt; 0.001) were found for the number of movements (A:712 ± 59, B:524 ± 49, C:452 ± 65). No differences were observed for the area under curve when examining perceived exertion between protocols. However, the values for perceived recovery significantly differed (p &lt; 0.001) between protocols (A:64 ± 19; B:52 ± 11; C:17 ± 13). Interestingly, protocol B and C induced a displeasure perception compared to protocol A. Our findings suggest that exercise distribution/order using HIIT whole body exercise promotes alterations in psychophysiological responses in HIIT using whole body exercises.

Attenuated Metabolic and Cardiorespiratory Responses to Isoenergetic High-Intensity Interval Exercise of Short Versus Long Bouts

PURPOSE

To compare the metabolic, cardiorespiratory and perceptual responses to three isoenergetic high-intensity interval exercise (HIIE) protocols of different bout duration and an isoenergetic continuous exercise protocol.

METHODS

Eleven healthy males (age, 28 ± 6 yr) performed four 20-min cycling trials of equal mean power output 1 wk apart. Participants cycled either continuously (CON) or intermittently with 10 s (HIIE10), 30 s (HIIE30), or 60 s (HIIE60) bouts at intensities corresponding to 49% (CON) or 100% of power at peak oxygen uptake (V̇O2peak). Recovery intervals during the HIIE trials were 15, 45, and 90 s, respectively.

RESULTS

Average V̇O2 was similar in the HIIE trials (2.29 ± 0.42, 2.20 ± 0.43, and 2.12 ± 0.45 L·min-1, for HIIE10, HIIE30, and HIIE60, respectively), whereas in CON (2.02 ± 0.38 L·min-1), it was lower than HIIE10 (P = 0.002) and HIIE30 (P = 0.043). Average pulmonary ventilation (VE) was higher in HIIE60 compared with HIIE10, HIIE30, and CON (75.8 ± 21.8 L·min-1 vs 64.1 ± 14.5 L·min-1, 64.1 ± 16.2 L·min-1, and 54.0 ± 12.5 L·min-1, respectively, P < 0.001). The peak values and oscillations of V̇O2 and VE in HIIE60 were higher compared with all other trials (P < 0.001). Blood lactate concentration was higher in HIIE60 compared with HIIE10, HIIE30, and CON from the fifth minute onward, reaching 12.5 ± 3.5, 7.2 ± 2.1, 7.9 ± 2.9, and 4.9 ± 1.6 mmol·L-1, respectively, at the end of exercise (P < 0.001). RPE was higher and affective responses were lower in HIIE60 compared with all other trials toward the end of exercise (P < 0.001).

CONCLUSIONS

These findings highlight the importance of bout duration in HIIE, since shorter bouts resulted in attenuated metabolic and cardiorespiratory responses, lower RPE and feelings of displeasure compared with a longer bout, despite equal total work, duration, and work-to-recovery ratio. These results may have implications for the prescription of HIIE in various populations.

A Pilot Study on In-Task Affect Predicting Free-Living Adherence to HIIT and MICT

Purpose: To report pilot test findings on whether in-task affect during a supervised exercise program, where participants were randomized to either moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT), predicts changes in moderate-to-vigorous physical activity (MVPA-Total and MVPA10+ in bouts of ≥ 10 min) at 1- and 6-month post-intervention. Method: This experimental study design randomized 32 inactive adults with prediabetes to complete a 2-week supervised MICT or HIIT plus behavioral counseling exercise intervention and objectively assessed free-living physical activity post-intervention. The Feeling Scale (FS) was used to assess the in-task effect. FS was measured in the middle of four, 1-min intervals in the HIIT condition, corresponding to ~20%, ~50%, ~75%, and ~85% of work out time. For the MICT condition, FS was assessed at similar exercise duration percentage times as HIIT. Accelerometer data evaluated MVPA at 1- and 6-month post-intervention. Results: 32 adults were included in the analyses. Pilot findings indicated in-task affect between the conditions did not predict changes in MVPA-Total from baseline to 1 and 6 months. For MVPA10+, in-task affect negatively predicted MVPA10+ over time in the MICT condition only. Conclusion: This study provides preliminary evidence that affect during MICT negatively predicts MVPA10+ over time, and that there is no difference of in-task affect's utility in predicting MVPA-Total between HIIT and MICT. Larger studies are required to confirm these findings.

The Effects of High-Intensity Multimodal Training in Apparently Healthy Populations: A Systematic Review

Background

High-intensity multimodal training (HIMT) is emerging as a popular training method that combines aerobic and resistance training throughout a single exercise session. The current literature is limited by a lack of terminology that broadly encompasses all styles of combined aerobic and resistance training. The magnitude of chronic or long-term (i.e.  ≥ 4 weeks) effects of HIMT participation on aerobic and muscular fitness also remains unclear. Additionally, one of many complex reasons for the growing popularity of HIMT may be attributed to the affective response to exercise, namely levels of enjoyment. However, this concept is not yet well understood across all styles of HIMT. A comprehensive systematic review is required to synthesise the available literature and attempt to provide an operational definition of HIMT to capture the breadth of combined training styles that exist.

Objective

The objective of this systematic review was to determine the chronic effects of HIMT participation on aerobic and muscular fitness and to compare HIMT to established concurrent training methods. Enjoyability and other adherence-related subjective responses were also examined in HIMT participants. This review critically assessed the level of evidence and feasibility of current HIMT guidelines.

Methods

A systematic literature search was conducted on PubMed, Web of Science and SPORTDiscus to identify studies up until March 2021.

Results

A total of 20 studies were included for review. Studies generally reported moderate to large effects on aerobic fitness and subjective responses in favour of HIMT interventions. Mixed outcomes were demonstrated in muscular fitness. These results should be treated with caution due to high risk of bias among included studies.

Conclusions

Few studies have assessed the chronic effects of HIMT participation on aerobic, and musculoskeletal adaptations and subjective responses, in particular exercise enjoyment. Research conclusions are limited by heterogeneity of experimental protocols and outcome measures. Furthermore, the inability of the literature to make adequate comparisons between various styles of HIMT and other concurrent training protocols limits understandings of the efficacy of HIMT.

Registration This systematic review was registered on the Open Science Framework (10.17605/OSF.IO/2RE4B; 26 March 2021).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-022-00434-x.

Using Bodyweight as Resistance Can Be a Promising Avenue to Promote Interval Training: Enjoyment Comparisons to Treadmill-Based Protocols

Purpose: Even though multiple training methods appear to be effective to improve cardiorespiratory fitness, they also need to be perceived as tolerable or enjoyable by exercisers to maximize long-term behavioral maintenance. Therefore, the purpose of the current study was to compare perceived enjoyment between whole-body interval training (SIT-WB), treadmill-based interval training (SIT-T) and moderate-intensity continuous training (MICT). Method: Forty-one healthy adult men (age: 23.7 ± 0.7 years, height: 1.79 ± 0.01 m, body mass: 78.5 ± 1.7 kg; VO_2max: 46.7 ± 7.3 ml.kg^-1.min^-1) were randomly assigned to SIT-WB, SIT-T, or MICT and underwent 16 weeks of training (3x/w). SIT-WB and SIT-T completed eight 20 s bouts interspersed by 10 s passive recovery, differing as to the exercise mode performed (i.e., calisthenics exercises and treadmill running, respectively) whereas MICT participants ran for 30 min at an intensity below the second ventilatory threshold. Perceived enjoyment was assessed 10 min post-exercise at weeks 1, 5, 9, 13, and 16, using the Physical Activity Enjoyment Scale. Results: Compliance was high (~90%) across all three training groups (p = .803). All training modes were rated as enjoyable and no significant within- (F_{(4, 152)} = 1.132, p = .344) or between-group (F_{(2, 38)} = 0.662, p = .521) differences were found during the intervention period. Conclusions: These results suggest that SIT-WB can be employed as an enjoyable low-cost alternative to traditional treadmill-based SIT and MICT for up to 16 weeks.

Perceptual Responses and Future Exercise Intentions of Individuals with Systemic Arterial Hypertension

To analyze the perceptual responses and future intentions (FI) to engage in continuous moderate aerobic exercise (CE) and high-intensity interval exercise (HIIE) of individuals with systemic arterial hypertension (SAH), we had 25 participants with SAH (M age=48.0, SD=8.0 years) perform, on different days and in randomized order, 33 minute sessions of CE and 30 minutes of HIIE. Twenty seconds after each 3-minutes of these sessions, we obtained participant responses to Ratings of Perceived Exertion (RPE), the Feeling Scale (FS), the Felt Arousal Scale (FAS), and attentional focus (AF). We assessed their FI to engage in CE and HIIE at the end of each session. We analyzed results using two-way ANOVAs with repeated measures, Spearman correlation coefficients, a simple linear regression and Wilcoxon test. We found a significant time by session type (CE and HIIE) interaction effect for RPE (F [2.05; 49.17] = 3.31; p < 0.001), FAS (F [2.43; 58.25] = 6.18; p = 0.002) and AF (F [2.56; 61.44] = 5.41; p = 0.004). Participants' FI to engage in HIIE were only significantly correlated with FAS (r = -0.424; p = 0.035) and AF (r =0.431; p = 0.032) responses. FAS responses (βz=-0.455; R2=0.207; p =0.022) and AF responses (βz=0.467; R2=0.218; p=0.019) predicted FI for engaging in HIIE. There were no significant differences in participants' FI to engage in CE sessions (M = 76.4, SD =22.5%) versus HIIE sessions (M = 71.8, SD = 22.9%; p=0.177). Individuals with SAH had more positive perceptions of CE than HIIE, as seen by their greater dissociative AF in the CE sessions. Furthermore, these results supported the application of strategies aimed at manipulating AF in this population, possibly as a tool to increase participants' FI to engage in subsequent physical exercise.

Modeling longitudinal variation in affective response to exercise across a 16-week randomized control trial (RCT)

Objective: Consistent with the Science of Behavior Change (SOBC) experimental medicine approach, this early phase intervention development study examines the influence of an intervention strategy (exercise training) on a behavioral health outcome (exercise engagement) in the service of addressing a widespread threat to public health (physical inactivity). Method: Physically inactive participants (N = 201) were randomly assigned to one of four exercise training conditions fully crossed on intensity (moderate, vigorous) and duration (short, long). Training occurred over 16-weeks and in-bout assessments of affective response (valence) and ratings of perceived exertion (RPE) were collected during Weeks 1, 4, 8, and 16. Cardiorespiratory fitness (VO₂max) was assessed pre- or postintervention and exercise behavior was assessed at 6-months postintervention follow-up. Results: Across conditions, affective response to exercise did not change, on average, over 16-weeks. Conversely, RPE decreased slightly, on average, over time. Participants completing vigorous intensity exercise reported more negatively valenced affective response and higher RPE, on average, across weeks. Greater total exercise volume completed and greater change in VO₂max were associated with more negatively valenced affective response, on average. Baseline affective response scores were positively associated with exercise minutes at follow-up; however, average affective response scores across the intervention were not associated with minutes of exercise at follow-up. Conclusions: Affective response to exercise did not become more positive in valence over time as a function of training volume or change in VO₂max. Implications for translating these findings to inform future intervention development efforts are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

ENERGY EXPENDITURE IN HIIT WHOLE BODY ASSOCIATED WITH ELECTROMYOSTIMULATION

ABSTRACT Introduction: The use of whole body electromyostimulation (WB-EMS) has been shown to be an efficient method for inducing significant improvements in muscle strength and performance outcomes. Hypothetically, WB-EMS had been considered an enhancer of energy expenditure in the session, but this remains unclear. Objective: In view of the lack of information, this study aims to evaluate the energy expenditure of WB-EMS associated with whole body High-Intensity Interval Training (HIIT). Methods: Fourteen male participants were submitted into two randomized exercise sessions: HIIT (whole body weight exercises without WB-EMS) and HIIT+WB-EMS (whole body weight exercises associated with WB-EMS). For both exercise conditions, the subjects performed whole body HIIT according to the following protocol: 3 minutes of warm-up followed by 4 exercises (30 seconds of stimulus) organized in 2 blocks, with 3 sets in each exercise, a rest period of 15 seconds between sets, and 180 seconds between blocks. The following exercises were performed: jumping jacks, squat and thrusts, burpees, and spider plank. Results: Significant differences were found in the absolute VO2 (HIIT:2.18±0.34, HIIT+WB-EMS:2.32±0.36 L.min−1) and relative VO2 (HIIT:26.30±3.77, HIIT+WB-EMS:28.02± 3.74 ml.kg.min−1), MET (HIIT:7.51±1.07, HIIT+WB-EMS:8.00±1.07), lactate concentration (HIIT:11.59±2.16, HIIT+WB-EMS: 12.64±1.99 mmol.L−1) and total energy expenditure (HIIT: 249.6± 45.04 Kcal, HIIT+ WB-EMS: 268.9±40.67 Kcal; 7.46 ± 5.31%). Conclusion: Our data indicate that the use of WB-EMS associated with HIIT generated a slightly higher metabolic demand than that of the control. However, the absolute differences do not allow us to indicate the superiority of WB-EMS, and future trials should be designed to determine the long-term effects.

A single session of low-volume high-intensity interval and moderate-intensity continuous exercise elicits a transient reduction in ghrelin levels, but not in post-exercise energy intake in obese men

OBJECTIVE

This study investigated the acute effects of high-intensity interval (HIIE) and moderate-intensity continuous (MICE) exercise on ghrelin levels in obese men.

METHODS

A total of 10 obese men (age 27.6 ± 1.8 years, body mass index 35.4 ± 4.5 kg/m2, body fat 39.9 ± 2.1%) performed two exercise sessions in a randomized order: HIIE (10 × 1 min intervals at 90% of the maximal heart rate [HRmax] interspersed by 1 min of active recovery) and MICE (20 min at 70% of the HRmax). Ghrelin levels were assessed pre-, post- and 1h post-exercise, and energy intake was assessed 1h post-exercise through an ad libitum meal.

RESULTS

HIIE and MICE showed a trend to decrease ghrelin levels immediately post-exercise (-14.1 ± 21.6% and -9.6 ± 23.8%, respectively, p = 0.07) and decreased 1h post-exercise (-12.7 ± 31.8% and -13.8 ± 21.7%, respectively, p < 0.05). No changes were observed for post-exercise energy intake (p > 0.05). There was a positive correlation between the change in ghrelin levels and post-exercise energy intake only for HIIE (r = 0.63, p = 0.05).

CONCLUSION

In summary, a single session of HIIE and MICE elicits a reduction on ghrelin levels without changing post-exercise energy intake in obese men.

Evidence-based vs. social media based high-intensity interval training protocols: Physiological and perceptual responses

OBJECTIVE

High intensity interval training (HIIT) is a time-efficient exercise modality to improve cardiorespiratory fitness, and has recently been popularised by social media influencers. However, little is known regarding acute physiological and perceptual responses to these online protocols compared to HIIT protocols used within research. The aim was to investigate acute physiological, perceptual and motivational responses to two HIIT protocols popular on social media, and compare these to two evidence-based protocols.

METHODS

Twenty-seven recreationally active (>1 exercise session /week) participants (Age: 22±3y, BMI: 24.3±2.4) completed a randomised cross-over study, whereby each participant completed four HIIT protocols, two already established in research (Ergo-60:60 (cycling 10x60s at 100%Wmaxwith 60s rest), BW-60:60 (body-weight exercises 10x60swith 60s rest)) and two promoted on social media (SM-20:10 (body-weight exercises 20x20swith 10s rest) and SM-40:20 (body-weight exercises 15x40s with 20s rest)). Blood lactate, heart rate (HR), feeling scale (FS), felt arousal scale (FSA), enjoyment and perceived competence were measured in response to each protocol.

RESULTS

Significant differences were observed between BW-60:60 and SM-20:10 for the proportion of intervals meeting the ACSM high-intensity exercise criterion (>80% of HRmax) (BW-60:60 93±10%, SM-20:10 74±20%, P = 0.039) and change in lactate (BW-60:60 +7.8±3.7mmol/L, SM-20:10 +5.5±2.6mmol/L, P = 0.001). The percentage of time spent above the criterion HR was also significantly lower in SM-20:10 compared to all other protocols (Ergo-60:60 13.9±4.9min, BW-60:60 13.5±3.5min, SM-40:20 12.1±2.4min, SM-20:10 7.7±3.1, P<0.05). No differences were observed in lowest reported FS between protocols (P = 0.268), but FS decreased linearly throughout Ergo-60:60 and BW-60:60 (first vs. last interval P<0.05), but not in SM-20:10 or SM-40:20 (P>0.05). Enjoyment was higher upon completion of BW-60:60 compared to Ergo-60:60 and SM-40:20 (P<0.05).

CONCLUSIONS

This study shows that HIIT protocols available on social media offer an interesting real-world alternative for promoting exercise participation. Future studies should continue to investigate these highly popular and practical HIIT protocols.

Acute affective responses to high-intensity interval exercise: Implications on the use of different stimulus-recovery amplitudes

The effect of high-intensity interval exercise (HIIE) on affective responses is unclear due to the several variables of HIIE, which may be minimized by using derived variables (e.g. amplitude). The amplitude reflects the difference between stimulus and recovery intensities, being more representative of the physiological changes than central tendency variables such as average intensity. This study aimed to compare the affective responses in HIIE sessions in different amplitudes with a vigorous-intensity continuous exercise (VICE) session. Eleven participants completed five sessions. The peak oxygen consumption (VO_2Peak) and peak power (W_peak) were measured. Participants performed one VICE and three HIIE sessions (10x[1min-90%W_Peak/1min-50%W_Peak]; 10x[1min-100%W_Peak/1min-40%W_Peak]; and 10x[1min-110%W_Peak/1min-40%W_Peak]). The exercise sessions were performed at the same average intensity (70%W_Peak) and duration (20 min). The Feeling Scale (FS) was applied in each minute throughout the exercise sessions. Regarding the FS responses, a two-way repeated-measures ANOVA showed no significant interaction for FS (P=0.093) or main effect for condition (P=0.206) and time (P=0.078), indicating that irrespective of the amplitude of the HIIE, FS results were similar between conditions. The effect size (ES) analysis showed a small effect in favour of HIIE-90/50 (ES=0.30) and HIIE-100/40 (ES=0.26) and a null effect on HIIE-110/30 (ES=0.08) when compared to VICE. Chi-squared analysis showed no significant differences between conditions in the number of participants that reduced, maintained, or increased the FS from pre-exercise to last stimulus and recovery indicating a high variability of the affective responses. HIIE sessions provide similar affective responses when performed at the same average intensity, even with different amplitudes.

Effects of Self-Selected Passive Recovery Time in Interval Exercise on Perceptual and Heart Rate Responses in Older Women: A Promissory Approach

The purpose of the study was to investigate the effects of passive recovery with self-selected time on affect, ratings of perceived exertion, and heart rate in self-selected interval exercises (SSIE). Fifteen older women (68.1 ± 3.8 years), weekly practitioners of functional activities participated in three SSIE with self-selected recovery time (SSRT) and one self-selected continuous exercise session, all at 24 min approximately. The SSIE had the following configurations: 1'/SSRT, 1.5'/SSRT, and 2'/SSRT. The results showed that at the beginning of stimulus heart rate in 1.5'/SSRT (107.9 ± 16.5) and 2'/SSRT (114.6 ± 17.1) were significantly greater (p < .05) compared with self-selected continuous exercise (102.8 ± 14.5). The ratings of perceived exertion in self-selected continuous exercise (2.4 ± 0.4; p < .05) were higher compared with SSIE in recovery. No significant differences were found in affect. The SSIE provided similar responses based on recoveries manipulations.

Effects of Exercise Structure and Modality on Physiological and Perceptual Responses to Exercise

ABSTRACT

Bogdanis, GC, Mallios, VJ, Katsikas, C, Fouseki, T, Holman, I, Smith, C, and Astorino, TA. Effects of exercise structure and modality on physiological and perceptual responses to exercise. J Strength Cond Res 35(9): 2427-2432, 2021-This study examined the effect of exercise mode and intensity on physiological and perceptual responses to exercise. Twelve active adults (6 men and 6 women, age = 21.7 ± 1.6 years) initially performed incremental testing on the treadmill (TM) and cycle ergometer (CE) to assess maximal oxygen uptake (V̇o2max) and ventilatory threshold (VT). During the next 4 visits in a randomized order, subjects performed 20 minutes of moderate-intensity continuous exercise (MICE) at an intensity 20% below VT on the TM (TMMICE) and cycle ergometer (CEMICE) as well as time-matched high-intensity interval exercise (HIIE; 10 1-minute bouts at workload equal to 20% above VT followed by 1-minute active recovery) on both modes (TMHIIE and CEHIIE). During exercise, gas exchange data, blood lactate concentration, and perceptual responses (rating of perceived exertion, affective valence, and enjoyment) were assessed. Heart rate (p < 0.001) and V̇o2 (p < 0.001) were higher in response to TMHIIE vs. CEHIIE as well as TMMICE vs. CEMICE. Blood lactate concentration was higher (p = 0.003) in response to CEHIIE vs. TMHIIE. The rating of perceived exertion was significantly higher (p < 0.001) in TMMICE compared with CEMICE which showed the most positive affective valence (p = 0.009). Enjoyment was similar across all bouts (p = 0.11). Treadmill-based HIIE leads to higher heart rate and V̇o2 vs. CEHIIE, although there was no difference in affective valence or enjoyment. Practitioners aiming to optimize the cardiorespiratory response to moderate or interval exercise in their clientele should recommend TM running rather than cycling.

Green Exercise: Can Nature Video Benefit Isometric Exercise?

Green exercise is the combination of physical activity and nature exposure, which has been associated with positive effects on psychophysiological health. This study aimed to investigate the effects of nature video viewing on isometric exercise and find a useful practice for green exercise in urban living. In the current study, 18 male subjects were recruited in a randomized crossover trial and underwent a sequence of wall squat exercises. The whole experiment contained three periods of baseline (before exercise), exercise, and recovery (after exercise), and each period lasted for 2 min. A video of forest walking was played in the exercise and recovery periods as treatment, while a black screen was set as control. The Rate of Perceived Exertion Scale (RPE) and Feeling Scale (FS) were employed to measure perceived exertion and affective responses in the exercise period; heart rate (HR) and heart rate variability (HRV) including the standard deviation of normal-to-normal RR intervals (SDNN), the root mean square of successive differences (RMSSD), and the standard deviations of the Poincaré plot (SD1), were recorded in the three periods. Heart rate recovery (HRR) in the recovery period was further calculated based on 30 s and 60 s time frames. Results demonstrated that during the exercise period nature video viewing was associated with better affective responses (median of 1.00 and an interquartile (IQR) of 2.00, p = 0.017), lower perceived exertion (median = 6.00, IQR = 2.00, p = 0.021), and lower HR (median = 89.60, IQR = 20.94, p = 0.01), but the differences in HRV indices between the experimental settings were not statistically significant. In the recovery period, significantly higher values of RMSSD (median = 34.88, IQR = 24.52, p = 0.004), SD1 (median = 24.75, IQR = 17.41, p = 0.003), and HR (median = 84.18, IQR = 16.58, p = 0.001) were observed in the treatment setting, whereas no statistically significant difference was found for HRR. In general, our findings support that nature video viewing may help reduce perceived exertion, increase exercise pleasure, buffer heart rate, and improve cardiac autonomic recovery for wall squat exercising, which implies the potential of nature-based stimuli in green exercise. However, due to the limited research sample, further study may need to include female participants and focus on various populations to confirm the effectiveness of using virtual and environments depicting nature at home or in public exercise places to promote positive exercise experience.

Might High-Intensity Interval Exercise Be Remembered as More Pleasurable? An Attempt to Test the Peak-End Rule in the Exercise Context

Given humans' limited ability to recall past experiences for evaluation, scholars have proposed the peak-end rule stating that if perceived discomfort at the end of an aversive experience is lower than the peak discomfort experienced, the aversive experience will be remembered more positively. The purpose of this study was to evaluate the peak-end rule as applied to high-intensity interval exercise (HIIE). Participants were 30 inactive men (M age = 27.9, SD =  5.2 years). In the first session they performed a graded exercise test on cycle-ergometer to determine their maximal aerobic power (MAP) (M = 233, SD = 35W); and, in the second and third sessions, they performed two HIIE protocols in randomized order: (a) Short trial - 20-minutes of HIIE, composed of 30-second efforts at 100% of MAP interspersed by 30-seconds of passive recovery; and (b) Long trial - 20-minutes of the short trial, plus 10-minutes more of HIIE, decreasing 3% of MAP in each additional bout, resulting in 70% of MAP in the last bout. During exercise, we recorded the participants' rating of perceived exertion (RPE) and affect, using the Feeling Scale (FS). At 30-minutes post-exercise, we again recorded the participants' affect, using the Global Affect Evaluation (GAE) and their session-RPE, and we recorded their enjoyment, using the Physical Activity Enjoyment Scale (PACES). In the last session, the participants chose a favorite protocol to repeat. All sessions were interspersed by at least 72 hours. The 10-minutes extra HIIE in the Long-trial condition resulted decreased heart rate values (M = 157, SD = 13bpm to M = 144, SD = 14bpm; p < 0.001), but psychological responses during and after exercise did not differ, nor did participants' preferred HIIE protocol. As the load drop for the Long-trial was not enough to change the psychological responses during exercise, there was no difference in the retrospective evaluation as the peak-end rule would have suggested.

Cognitive-Perceptual-Affective-Motivational Dynamics During Incremental Workload Accounting for Exertion Tolerance

Inquiry of the psychological states during the exercise experience failed to fully account for the role of motivation to adhere and the disposition of exertion tolerance (ET). The current study expands the scope of the integrated cognitive-perceptual-affective framework by measuring the motivation to sustain effort in two physical tasks and accounting for ET. Thirty male participants performed cycling and isometric handgrip tasks to assess the progression of the rating of perceived exertion, attentional focus, affective responses, and motivation to adhere, along with an incremental workload. The ET was determined by a handgrip task time to voluntary exhaustion. The findings indicated significant time effects and linear trends for perceived exertion, attentional focus, affect, and perceived arousal but not motivation to adhere during the handgrip and cycling tasks. The ET played a key role in the integrity of the model, particularly in perceptual, attentional, and affective responses. The intended model serves to stimulate new research into adaptation mechanisms.

Affective Determinants of Physical Activity: A Conceptual Framework and Narrative Review

The literature on affective determinants of physical activity (PA) is growing rapidly. The present paper aims to provide greater clarity regarding the definition and distinctions among the various affect-related constructs that have been examined in relation to PA. Affective constructs are organized according to the Affect and Health Behavior Framework (AHBF), including: (1) affective response (e.g., how one feels in response to PA behavior) to PA; (2) incidental affect (e.g., how one feels throughout the day, unrelated to the target behavior); (3) affect processing (e.g., affective associations, implicit attitudes, remembered affect, anticipated affective response, and affective judgments); and (4) affectively charged motivational states (e.g., intrinsic motivation, fear, and hedonic motivation). After defining each category of affective construct, we provide examples of relevant research showing how each construct may relate to PA behavior. We conclude each section with a discussion of future directions for research.

Effects of Self-selected Resistance Training on Physical Fitness and Psychophysiological Responses in Physically Inactive Older Women: A Randomized Controlled Study

This study aimed to investigate the effects of a 12-week self-selected resistance training (SSRT) program on physical fitness and psychophysiological responses among physically inactive older women. We randomly allocated 32 inactive older women (M age = 66.0 years, SD = 3.0) into either an SSRT (n = 16) or control group (n = 16). Participants performed SSRT three times per week over 12 weeks. We assessed maximal isotonic and isokinetic muscle strength, functional capacity, flexibility, cardiorespiratory fitness, and body composition at baseline and after the intervention. Affective responses and perceived exertion were evaluated after each exercise set throughout the training program. The SSRT group significantly improved their maximal muscle strength in all exercises (Cohen's d ranging from 1.4-3.3; all p's < .001), peak torque (knee flexors: d = 1.7; knee extensors: d = 1.6; all p < .001), flexibility (knee flexors: d = 1.7; single hip flexors: d = 1.6; all p < .001; bilateral hip flexors: d = 1.1, p = .001), fat-free mass (d = .9, p = .008), and cardiorespiratory fitness (d = .9, p = .014), compared to the control group. All components of functional capacity improved compared to the control group (Cohen's d ranging from .8 to 5.5; all p's ≤ .001). Participants perceived the exercise training sessions as pleasant and of low to moderate effort. Thus, a 12-week SSRT program was effective at improving physical fitness and inducing feelings of pleasure among inactive older women.

Effects of Cardiovascular Interval Training in Healthy Elderly Subjects: A Systematic Review

The aim of this review is to demonstrate the effects of cardiovascular interval training (IT) on healthy elderly subjects. We used the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. The following variables were observed: resting heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MBP), heart rate variability (HRV), baroreflex activity (BA), and maximal oxygen uptake (VO_2max). Studies were searched for in the MedLine, PubMed, and Sport Discus databases considering publications between 1990 and 2019. To find the studies, the keywords used were “Interval and Elderly Training” or “Interval Training and Baroreflex Sensing” or “Interval Training and Aging and Pressure Arterial and Blood Pressure Training” or “Interval Training and Variation in Aging and Heart Rate” or “Interval Training and Sensitivity to the Elderly and Baroreflex” or “Interval Training and Variability in the Elderly and Heart Rate.” The systematic search identified 1,140 hits. The analysis of the study was performed through a critical review of the content. One thousand one hundred forty articles were identified. Of these, 1,108 articles were excluded by checking the articles and abstracts. Finally, 32 studies were selected for full reading while 26 studies were eliminated because they did not contain a methodology according to the purpose of this review. Thus, six studies were included for the final analysis. The PEDro score was used for analyzing the study quality and found 4,8 ± 1,3 points (range: 3–6). Positive results were found with the different IT protocols in the observed variables. Results show that IT protocols can be an efficient method for functional improvement of cardiovascular and cardiorespiratory variables in the healthy elderly, especially HR, SBP, DBP, MAP, HRV, BA, and VO_2max. However, this method can be included in the prescription of aerobic training for the elderly to obtain conditional improvements in the cardiovascular system, thus being an important clinical intervention for the public.

Affective responses to high-intensity interval training with continuous and respite music

Music has been shown to enhance affective responses to continuous exercise, but the most effective application of music during interval exercise is poorly understood. This study examined two contrasting applications of music designed to assuage the decline in pleasure often experienced during high-intensity interval training (HIIT). In a repeated measures crossover design, 18 recreationally active participants (10 men and 8 women; M _age = 25.1 ± 5.1 years; M _BMI = 23.08 ± 2.01 kg/m 2; M VO_2max = 38.82 ± 10.73 ml/kg/min) completed three HIIT sessions (10 x 60 s efforts at 100% Wmax, separated by 75 s recovery) on a cycle ergometer. Participants completed two experimental conditions: respite music (applied only during the recovery periods), continuous music (applied throughout the entire HIIT session); and a no-music control condition. Results indicated that music did not influence affective valence during the work bouts or recovery periods of the HIIT sessions (ps >.05), but that listening to music continuously elicited greater post-task enjoyment (p =.032, d = 0.66) and remembered pleasure (p =.044, d = 0.5). This study is the first to investigate the application of music during a practical HIIT protocol and to compare the effects of respite versus continuous music during interval exercise.

Continuous walking and time- and intensity-matched interval walking: Cardiometabolic demand and post-exercise enjoyment in insufficiently active, healthy adults

We compared cardiometabolic demand and post-exercise enjoyment between continuous walking (CW) and time- and intensity-matched interval walking (IW) in insufficiently active adults. Sixteen individuals (13 females and three males, age 25.3 ± 11.1 years) completed one CW and one IW session lasting 30 min in a randomised-counterbalanced design. For CW, participants walked at a mean intensity of 65-70% predicted maximum heart rate (HR_max). For IW, participants alternated between 3 min at 80% HR_max and 2 min at 50% HR_max. Expired gas was measured throughout each protocol. Participants rated post-exercise enjoyment following each protocol. Mean HR and V˙O₂ showed small positive differences in IW vs. CW (2, 95%CL 0, 4 beat.min^-1; d = 0.23, 95%CL 0.06, 0.41 and 1.4, 95%CL 1.2 ml.kg^-1.min^-1, d = 0.36, 95%CL 0.05, 0.65, respectively). There was a medium positive difference in overall kcal expenditure in IW vs. CW (25, 95%CL 7 kcal, d = 0.58, 95%CL 0.33, 0.82). Post-exercise enjoyment was moderately greater following IW vs. CW (9.1, 95%CL 1.4, 16.8 AU, d = 0.62, 95%CL 0.06, 0.90), with 75% of participants reporting IW as more enjoyable. Interval walking elicits meaningfully greater energy expenditure and is more enjoyable than CW in insufficiently active, healthy adults.

Positive Affective and Enjoyment Responses to Four High-Intensity Interval Exercise Protocols

Several variables can be manipulated to compose high-intensity interval exercise (HIIE) protocols, and these different combinations may evoke different psychological responses (affect, enjoyment, mood, and perceived exertion). This study investigated psychological responses during four HIIE protocols. Following anthropometric measurements and two maximal exercise tests, 23 physically inactive adults (11 males [M_age = 25.6, SD = 4.8 years; M_{body mass} = 68.5, SD = 12.2 kg; M_height = 1.72, SD = 0.08 m] and 12 females [M_age = 25.0, SD = 3.5 years; M_{body mass} = 57.2, SD = 8.7 kg; M_height = 1.59, SD = 0.06 m]) performed four different types of HIIE on different days: (a) Long-interval HIIE (HIIE_L-10 × 60 seconds:60 seconds), (b) Short-interval HIIE (HIIE_S-2 blocks of 10 × 30 seconds:30 seconds with 120 seconds between blocks), (c) Repeated Sprint Training (19 × 6 seconds all out:40 seconds), and (d) Sprint Interval Training (4 × 30 seconds all-out efforts: 240 seconds). We used a final session to assess participants' HIIE preference. We recorded participant reports of affect, mood, and perceived exertion throughout protocols, and we recorded enjoyment after exercise session. Perceived exertion significantly increased across all HIIE protocols (p < .001), with higher values in the first quartile during Sprint Interval Training versus HIIE_L (p = .033). Affective response presented higher values pre-exercise and at the first quartile compared with all other moments (p < .001). Tension (p < .001) and depression (p = .013) decreased from pre- to post-exercise in all experimental conditions. At pre-exercise, female participants were tenser than males (p = .018), though males presented higher pre-exercise vigor scores than females (p = .023). Vigor increased over time for females (p = .022). Enjoyment did not vary between sexes or protocols. Participants expressed a higher preference for Repeated Sprint Training. HIIE protocols promoted positive psychological responses for physically inactive young adults, and exercise designs may modulate psychological responses.

How Do Patients With Axial Spondyloarthritis Experience High-Intensity Exercise?

Objective

In a few studies, high‐intensity exercise has displayed beneficial effects on cardiovascular health among patients with rheumatic diseases, yet the high‐intensity exercise mode is still not fully accepted among health care professionals. The aim of this study was to investigate experiences of high‐intensity exercise among patients with axial spondyloarthritis.

Methods

Fourteen respondents who had participated in a high‐intensity exercise program for 12 weeks were included in this qualitative study with individual semistructured, in‐depth interviews. The respondents’ median age was 53, ranging from 23 to 63 years old, and both men and women of different ethnicities were represented. Interviews were analyzed by qualitative content analysis, including both manifest content and interpretations of underlying latent meaning.

Results

The analysis resulted in five categories describing the respondents’ experiences with high‐intensity exercise: 1) high‐intensity exercise as a challenge for both body and mind, 2) increased faith in one's own body, 3) changed attitude toward exercise, 4) taking charge of one's own health by challenging the disease, and 5) exercise in a social context.

Conclusion

Supervised high‐intensity interval exercise was perceived as challenging for both body and mind but was also described as a positive experience, with rapid bodily effects that strengthened respondents’ faith in their own bodies. The new experience seemed to have changed the respondents’ attitude and motivation for exercise and made them start taking charge of their health by challenging the disease. Exercise in a social context, under professional leadership, enhanced exercise self‐efficacy and helped the respondents to adhere to the exercise program.

Time-efficient and computer-guided sprint interval exercise training for improving health in the workplace: a randomised mixed-methods feasibility study in office-based employees

Background

The efficacy of high-intensity interval training (HIT) as a time-efficient exercise strategy for beneficially modifying risk factors for cardiovascular disease has repeatedly been demonstrated in controlled laboratory settings. However, the effectiveness of HIT in an unsupervised workplace setting has not been investigated. The objective of this study was to use mixed methods to investigate the feasibility, acceptability and effectiveness of a short-duration, high-intensity exercise intervention (REHIT) when applied unsupervised in a workplace setting.

Methods

Twenty-five office-workers (mean ± SD age: 47 ± 9 y, BMI: 27.5 ± 4.4 kg·m^− 2, V̇O₂max: 28 ± 7 mL·kg^− 1·min^− 1) completed a 6-week REHIT intervention unsupervised in their workplace (n = 13, 6 men), or acted as a no-intervention control (n = 12, 6 men). The intervention consisted of 2 sessions/week of low-intensity (~ 25 W) cycling interspersed with 2 ‘all-out’ sprints, increasing in duration from 10 to 20 s per sprint over the 6 weeks (total time-commitment: 8:40 min per session). V̇O₂max was assessed pre- and post-training, whilst questionnaire-based measures of exercise enjoyment, self-efficacy, and acceptability were completed post-training. Eight participants also completed post-intervention semi-structured interviews.

Results

V̇O₂max significantly improved in the exercise group (2.25 ± 0.75 L·min^− 1 vs. 2.42 ± 0.82 L·min^− 1; + 7.4%) compared to the control group (2.22 ± 0.72 L·min^− 1 vs. 2.17 ± 0.74 L·min^− 1; − 2.3%; time*intervention interaction effect: p < 0.01). Participants considered the REHIT intervention acceptable and enjoyable (PACES: 89 ± 17 out of 119) and were confident in their ability to continue to perform REHIT (7.8 ± 1.2 out of 9). Qualitative data revealed that REHIT offered a time-efficient opportunity to exercise, that was perceived as achievable, and which encouraged highly valued post-exercise outcomes (e.g. progress towards health/fitness benefits).

Conclusions

REHIT could be implemented as a feasible, effective and acceptable exercise intervention in a workplace setting, with a total time-commitment of < 20 min/week. Consideration of certain psycho-social factors and behaviour-change techniques may ensure adherence to the REHIT programme in the long term.

Trial registration

The study was registered on ClinicalTrials.gov on 07/05/2019 (registration: NCT03941145).

Affective and Enjoyment Responses to Short-Term High-Intensity Interval Training with Low-Carbohydrate Diet in Overweight Young Women

Low-carbohydrate diets (LCs) seem effective on weight reduction and maintenance. However, the affect and enjoyment of exercise during LCs is not clear. The purpose of the present study was to compare the psychological responses to high-intensity interval training (HIIT) and to moderate-intensity continuous training (MICT) during the consumption of a 4-week LC diet in overweight young women. With LCs (~10% carbohydrate, 65%–70% fat, 20%–25% protein), forty-three eligible women (age: 20.9 ± 3.1 years; body weight: 65.8 ± 8.2 kg) were randomly assigned to one of three groups: HIIT (10 sets of 6 s all-out cycling interspersed with 9 s of rest), MICT (30 min cycling at 50%–60% of peak oxygen consumption, V̇O_2peak) or no-exercise controls (CON). Anthropometric indices and V̇O_2peak were measured pre- and post-training. Feeling Scale (FS), Felt Arousal Scale (FAS), Exercise Enjoyment Scale (EES), and Physical Activity Enjoyment Scale (PACES) scores were collected before and immediately after each training session throughout the study. After intervention, all three groups reduced by more than 2.5 kg of body weight whereas both exercise groups improved ~15% V̇O_2peak. Participants in the HIIT and MICT group exhibited similar affect points as indicated by FS and FAS. Post-exercise enjoyment scores in PACES were lower in HIIT (73–78 points) than MICT (83–87 points) despite similarly positive responses being observed in EES (corresponding to ~4 points of a 7-point scale). Short-term LCs were effective in weight loss and exercise training had an additive improvement on cardiorespiratory fitness. The overweight young women had similar affect valence, arousal levels, and comparable pleasurable feelings to HIIT and MICT with LCs. Furthermore, as indicated by PACES, MICT was more enjoyable which may elicit better adherence, whereas HIIT with LCs seems to be more arduous despite its time-efficiency.

Similar perceptual responses to reduced exertion high intensity interval training (REHIT) in adults differing in cardiorespiratory fitness

Reduced exertion high intensity interval training (REHIT) is an extremely low-volume approach of sprint interval exercise (SIE) that increases maximal oxygen uptake (VO₂max) and reduces body fat. However, there are concerns regarding implementation of SIE including REHIT in untrained populations due to generation of supramaximal power outputs and potential feelings of displeasure. This study examined perceptual responses to a single REHIT session in adults with above (n = 43, VO₂max = 41 ± 6 mL/kg/min) and below average VO₂max (n = 42, VO₂max = 33 ± 5 mL/kg/min). Initially, incremental exercise was completed to determine VO₂max. Subsequently, participants completed REHIT consisting of two 20 s "all-out" sprints at resistance equal to 5 % body mass. Rating of perceived exertion (RPE), affective valence, and physical activity enjoyment (PACES) were determined. Tolerance and preference to exercise intensity were also measured to examine if they moderated the responses. Compared to participants with below average VO₂max, those with above average VO₂max revealed similar change in affective valence (p = 0.86), RPE (p = 0.41), and enjoyment (p = 0.64) despite attaining significantly higher peak and mean power output in response to REHIT. The lowest value of affective valence ranged from 1.0-1.5, representing "fairly good." Overall, one session of REHIT elicits positive affective valence and similar pleasure:displeasure and enjoyment responses in individuals having diverse cardiorespiratory fitness, although we recommend that REHIT should be individualized for each client as greater frequency of aversive responses was shown in our participants with low fitness.

Effects of High-Intensity Interval and Moderate-Intensity Continuous Exercise on Physical Activity and Sedentary Behavior Levels in Inactive Obese Males: A Crossover Trial

A total of 17 participants (30.2 ± 4.8 years; 35.4 ± 4 kg/m2; 38.2 ± 3.6 % body fat) were enrolled in this randomized crossover trial to analyze the effects of a single session of high-intensity interval (HIIE) and moderate-intensity continuous exercise (MICE) on the physical activity and sedentary behavior levels in inactive obese males. The participants performed two exercise sessions and one control session (no exercise): i) low-volume HIIE (10 x 60 s at 90% of maximal aerobic velocity [MAV] interspaced by 60 s at 30% of MAV); ii) MICE (20 min at 70% of maximum heart rate); and iii) control (25 min in a seated position). After all sessions, the physical activity and sedentary behavior levels were monitored by accelerometer over seven consecutive days. No differences in the physical activity (activity counts, and time spent at light, moderate, and vigorous intensities) and sedentary behavior (time spent at sedentary behavior, breaks, and bouts) levels were found among the sessions (HIIE, MICE and control) (p > 0.05). In summary, a single session of HIIE and MICE does not change the physical activity and sedentary behavior levels in inactive obese males. Therefore, low-volume of both high- and moderate-intensity exercise should be considered for inactive obese males given that it does not reduce the physical activity level or increase the time spent at sedentary behavior.

Timed consumption of a New Zealand blackcurrant juice support positive affective responses during a self-motivated moderate walking exercise in healthy sedentary adults

BACKGROUND

Affective responses experienced during exercise are a significant determinant on exercise adherence. We have previously demonstrated that consumption of New Zealand (NZ) blackcurrants preserves cognition by attenuating the feeling of fatigue. This positive affective response correlated with the ability of blackcurrant polyphenols to support monoamine neurotransmission via inhibition of monoamine oxidase-B (MAO-B) activity. Here we explore how the consumption of a NZ blackcurrant juice (BJ) influenced affective responses and potential ergogenic action on the motivation to adhere to a low impact walking exercise.

METHODS

In a parallel randomized controlled study (Trial registration #: ACTRN12617000319370p, registered 28th February 2017, http://www.anzctr.org.au/ ), 40 healthy sedentary male and female participants drank a BJ or matched placebo (PLA) (n = 20 per group), 1 h prior to a self-motivated treadmill walk, where heart rate and affective responses (exertion [ES] or feeling / mood [FS]) scores) were recorded at 3 or 5 min intervals. Blood glucose, lactate, malondialdehyde (MDA) and platelet MAO-B activity were measured pre- and post-exercise and comparisons were conducted using with Student's t-tests. Subjective data were analysed using 2-way ANOVA with appropriate post hoc tests.

RESULTS

Consuming a BJ 1 h prior to exercise caused a 90% decline in platelet MAO-B activity. The exercise had no significant (p > 0.05) effect on blood lactate, glucose or plasma MDA levels. Assessment of affective responses over the first 60 mins (adjusting for participant drop-out) revealed a time-dependent ES increase in both groups, with ES reported by participants in the BJ group consistently lower than those in the PLA group (p < 0.05). FS declined in PLA and BJ groups over 60 mins, but an inverse relationship with ES was only observed within the PLA group (r2 = 0.99, p = 0.001). Whilst the average time walked by participants in the BJ group was 11 mins longer than the PLA group (p = 0.3), and 30% of the BJ group achieving > 10 km compared to only 10% for the PLA group (p = 0.28), statistical significance was not achieved.

CONCLUSION

Our findings demonstrate that drinking a polyphenolic-rich NZ blackcurrant juice 1 h prior to exercise supports positive affective responses during a self-motivated exercise.

Comparison of perceptual responses between different upper-body sprint interval exercise protocols

This study examined the perceptual responses to various upper-body sprint interval exercise (SIE) protocols matched for total work and work/rest ratio. Fourteen active men (24 ± 4 years, BMI = 26.2 ± 2.7 kg/m², body fat = 11.5 ± 4.4%) participated in 3 all-out SIE protocols consisting of battling rope exercise: P10:30 (12 × 10-s bouts with 30-s recovery); P15:45 (8 × 15-s bouts with 45 s recovery); and P30:90 (4 × 30-s bouts with 90-s recovery). During exercise, affective valence (FS +5 to -5), arousal (FAS 1-6), rating of perceived exertion (RPE 6-20), and heart rate (HR) were assessed. Post-exercise, enjoyment, self-efficacy, and intentions were measured. Results revealed a significant decline in FS (p = .02; partial eta squared [η²_p] = 0.27) and a progressive increase in FAS (p = .001; η²_p = 0.86), RPE (p = .001; η²_p = 0.88), and HR (p = .001; η²_p = 0.94), but no protocol X time interaction. Affective valence reached a nadir at values equal to -0.36 ± 3.41 (Cohen's d = -0.49), -0.43 ± 3.75 (Cohen's d = -0.44), and - 0.93 ± 3.49 (Cohen's d = -0.56) in response to P10:30, P15:45, and P30:90, respectively. There were no differences between protocols for enjoyment, intention, or self-efficacy. A negative relationship exhibited between FS and RPE was moderated by participants' tolerance of exercise intensity (β = 1.84, p < .05). Further, the association between FS and future intention was mediated by self-efficacy. Overall, upper-body SIE protocols exhibit similar perceptual responses when volume and work to rest ratio (1:3) are matched. Tolerance of exercise intensity may be used to predict changes in FS during SIE.

Progressive high-intensity interval training (HIIT) is not superior to unmodified non-progressive HIIT in an uncontrolled setting

BACKGROUND

High-intensity interval training (HIIT) is an important training component to improve aerobic and anaerobic exercise capacity. Higher HIIT workloads in general may generate additional effects on the improvement of exercise capacity, while missing adherence to more strenuous training regimes may affect training success. This study investigated if higher training workload generated by progressive HIIT (proHIIT) is superior to HIIT when used in an uncontrolled setting.

METHODS

Thirty-four moderately trained females and males performed a 4-week training intervention with three exercise sessions per week. Participants were randomized into two HIIT groups using the individual lactate threshold at baseline: Group 1 (N.=17), HIIT, four runs at maximal speed (all-out) with 30 s active recovery (total: 48 runs), Group 2 (N.=17), proHIIT, 4 runs at maximal speed (all-out) with 30-second active recovery with one extra repetition every week (up to seven runs, for a total of 66 runs). An incremental field test protocol with standard blood lactate (LA) diagnostic and heart rate monitoring was used to access changes in exercise capacity.

RESULTS

Overall, power output (running speed) at LA threshold (baseline LA+1.5 mmol/L) increased by +3.6% (P=0.004, effect size [ES] 0.38) after 4 weeks of HIIT. However, no significant between-group differences pre- vs post-intervention were detected.

CONCLUSIONS

Our data suggest that proHIIT does not provide additional improvement of running speed at individual lactate threshold over HIIT in an uncontrolled setting.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Physiological and Psychological Responses during Low-Volume High-Intensity Interval Training Sessions with Different Work-Recovery Durations

We compared physiological and psychological responses between low-volume high-intensity interval training (LV-HIIT) sessions with different work-recovery durations. Ten adult males performed two LV-HIIT sessions in a randomized, counter-balanced order. Specifically, 60/60 s LV-HIIT and 30/30 s LV-HIIT. Oxygen uptake (VO₂), carbon dioxide output (VCO₂), ventilation (VE), respiratory exchange ratio (RER), perceived exertion (RPE), and affect were assessed. During intervals, the VO₂ (3.25 ± 0.57 vs. 2.83 ± 0.50 L/min), VCO₂ (3.15 ± 0.61 vs. 2.93 ± 0.58 L/min), VE (108.59 ± 27.39 vs. 94.28 ± 24.98 L/min), and RPE (15.9 ± 1.5 vs. 13.9 ± 1.5) were higher (ps ≤ 0.01), while RER (0.98 ± 0.05 vs. 1.03 ± 0.03) and affect (-0.8 ± 1.4 vs. 1.1 ± 2.0) were lower (ps ≤ 0.007) in the 60/60 s LV-HIIT. During recovery periods, VO₂ (1.85 ± 0.27 vs. 2.38 ± 0.46 L/min), VCO₂ (2.15 ± 0.35 vs. 2.44 ± 0.45 L/min), and affect (0.6 ± 1.7 vs. 1.7 ± 1.8) were lower (ps ≤ 0.02), while RER (1.20 ± 0.05 vs. 1.03 ± 0.05; p < 0.001) was higher in the 60/60 s LV-HIIT. Shorter LV-HIIT (30 s) elicits lower physiological response and attenuated negative affect than longer LV-HIIT (60 s).

Reduced Exertion High-Intensity Interval Training is More Effective at Improving Cardiorespiratory Fitness and Cardiometabolic Health than Traditional Moderate-Intensity Continuous Training

This study sought to determine the effectiveness of an 8 wk reduced-exertion high-intensity interval training (REHIT) at improving cardiorespiratory fitness (CRF) and positively modifying cardiometabolic health in the workplace environment. Participants (n = 32) were randomized to two groups: (1) One group (n = 16) was prescribed an 8 wk REHIT program, and (2) one group (n = 16) was prescribed moderate-intensity continuous training (MICT). Cardiometabolic risk factors and CRF were measured at baseline and 8 wks. After 8 wks, changes in CRF (REHIT, 12%; MICT, 7%), systolic blood pressure (REHIT, −5%; MICT, −2%), waist circumference (REHIT, −1.4%; MICT, −0.3%), and metabolic syndrome (MetS) severity (MetS z-score: REHIT, −62%; MICT, 27%) were more favorable (p < 0.05) in the REHIT group relative to the MICT group. Interestingly, there was a significantly greater proportion of participants in the REHIT group (75%, 9/12) who had a favorable change in the MetS z-score (Δ > −0.60) relative to the MICT group (47%, 7/15). The main finding of the present study is that 8 wks REHIT elicited more potent and time-efficient improvements in CRF and cardiometabolic health when compared to traditional MICT. This study provides critical evidence for implementation of the sprint interval training (SIT) paradigm from the scientific literature into a real-world workplace setting.

Modality-specific training adaptations - do they lead to a dampened acute inflammatory response to exercise?

While adaptations to a short-term training program can dampen the acute inflammatory response to exercise, less is known about the influence of chronic modality-specific adaptations to training. This study compares the acute inflammatory response to upper- and lower-body interval exercise in individuals chronically trained in these respective modalities. Ninety minutes of interval exercise matched for relative power output on an arm-crank (ARM) and cycle ergometer (LEG) was performed by 8 trained paddlers and 8 trained cyclists. Blood samples were taken before and after exercise. Interleukin-6 (IL-6) concentrations were analysed in plasma, while the expression of intracellular heat shock protein 72 (iHsp72) was assessed in monocytes. IL-6 was increased following both modalities (fold change - ARM: 7.23 ± 3.56, p < 0.001; LEG: 9.03 ± 4.82, p < 0.001), in both groups (cyclists, p < 0.001; paddlers, p < 0.001), but the increase was smaller in ARM compared with LEG (time × modality, p < 0.001). ARM induced a smaller iHsp72 response compared with LEG (fold change - ARM: 1.07 ± 0.14, p = 0.102; LEG: 1.18 ± 0.14, p < 0.001; time × modality, p = 0.039). Following ARM, iHsp72 expression was increased in the cyclists only (fold change cyclists: 1.12 ± 0.11, p = 0.018; paddlers: 1.03 ± 0.17, p = 0.647), while iHsp72 expression following LEG was increased in both groups (fold change cyclists: 1.14 ± 0.15, p = 0.027; paddlers: 1.22 ± 0.13, p < 0.001). Taken together, the acute inflammatory response to lower-body interval exercise was larger compared with work-matched upper-body interval exercise. Moreover, adaptations to upper-body exercise training dampened the iHsp72 response to this modality. Therefore, exercise may be less effective in reducing chronic low-grade inflammation in individuals relying on their upper body, such as wheelchair users.

Psychological responses, muscle damage, inflammation, and delayed onset muscle soreness to high-intensity interval and moderate-intensity continuous exercise in overweight men

We compared in-task affect to HIIE and MICE, and its relationship with time spent at different metabolic domains, perceived exertion (RPE), self-efficacy, enjoyment, and future intention of exercise in overweight inactive men. Muscle damage and soreness, and inflammation were assessed post-exercise. Fifteen participants (28.9 ± 5.0 yr; 29.2 ± 3.8 kg/m²) completed a HIIE (10 × 1 min at 100% V_max, 1 min recovery) and MICE (20 min at 55-59% VO_2reserve) session. Affect, alertness, RPE, and self-efficacy were assessed in-task, and enjoyment and future intention post-task. At baseline, 24 and 48 h, creatine kinase, lactate dehydrogenase, interleukin-6 and -10, tumor necrosis factor alpha, and muscle soreness were assessed. Affect (-3.1 ± 1.8 vs. 0.8 ± 1.8, P < .001) and self-efficacy (70 ± 15 vs. 90 ± 15%, P < .001) were lower, while RPE and alertness were higher in HIIE compared to MICE (Ps ≤ .02). Affect was negatively correlated with RPE in HIIE (r = -0.90) and MICE (r = -0.72), and time spent above respiratory compensation point in HIIE (r = -0.59). Affect was positively correlated with self-efficacy in MICE (r = 0.74). Enjoyment, future intention, muscle damage and soreness, and inflammation were similar between HIIE and MICE post-exercise. Therefore, in-task HIIE was experienced as unpleasant compared to MICE, but the psychological and physiological responses post-task were similar in overweight inactive men.

Short-Term Psychological and Physiological Effects of Varying the Volume of High-Intensity Interval Training in Healthy Men

We assessed the short-term effects of varying the volume of high-intensity interval training (HIIT) on psychological and physiological responses of 23 healthy adult males ( M = 21 years; M peak oxygen uptake [VO2peak] = 47.2 ml·kg−1·min−1). Participants were randomly assigned to low- and very-low-volume HIIT groups and engaged in nine supervised exercise sessions over three weeks. The low-volume HIIT group performed 8-12 60-second work bouts on a cycle ergometer at the peak power output achieved during the incremental test, interspersed by 75 seconds of low-intensity active recovery. The very-low-volume HIIT performed 4-6 work bouts with the same intensity, duration, and rest intervals. During training, participants’ ratings of perceived exertion (Borg Category Ratio-10 scale) and their affective responses (Feeling Scale −5/+5) during the last 15 seconds of each work bout were recorded. Physiological data were VO2peak, endurance, and anaerobic performance before and after the intervention. Throughout training, participants in the very-low-volume group (relative to the low-volume group) reported lower ratings of perceived exertion in Week 1 ( M = 4.1 vs. M = 6.3; p < .01) and Week 3 ( M = 4.0 vs. M = 6.2; p < .01), and higher affective response in these same two weeks (Week 1: M = 1.9 vs. M = 0.3; p = .04; Week 3: M = 2.1 vs. M = 0.9; p = .06). Regarding physical fitness, Wingate peak power increased significantly after training in the very-low-volume HIIT group ( M = 1,049 W vs. M = 1,222 W; p < .05), but not in the low-volume HIIT group ( M = 1,050 W vs. M = 1,076 W). No significant change was found after training in physiological variables of peak power output, VO2peak, and endurance performance. In summary, in this short-term training period, the very-low-volume HIIT enhanced anaerobic capacity and was perceived as less strenuous and more pleasurable than low-volume HIIT.

Research into the Health Benefits of Sprint Interval Training Should Focus on Protocols with Fewer and Shorter Sprints

Over the past decade, it has been convincingly shown that regularly performing repeated brief supramaximal cycle sprints (sprint interval training [SIT]) is associated with aerobic adaptations and health benefits similar to or greater than with moderate-intensity continuous training (MICT). SIT is often promoted as a time-efficient exercise strategy, but the most commonly studied SIT protocol (4–6 repeated 30-s Wingate sprints with 4 min recovery, here referred to as ‘classic’ SIT) takes up to approximately 30 min per session. Combined with high associated perceived exertion, this makes classic SIT unsuitable as an alternative/adjunct to current exercise recommendations involving MICT. However, there are no indications that the design of the classic SIT protocol has been based on considerations regarding the lowest number or shortest duration of sprints to optimise time efficiency while retaining the associated health benefits. In recent years, studies have shown that novel SIT protocols with both fewer and shorter sprints are efficacious at improving important risk factors of noncommunicable diseases in sedentary individuals, and provide health benefits that are no worse than those associated with classic SIT. These shorter/easier protocols have the potential to remove many of the common barriers to exercise in the general population. Thus, based on the evidence summarised in this current opinion paper, we propose that there is a need for a fundamental change in focus in SIT research in order to move away from further characterising the classic SIT protocol and towards establishing acceptable and effective protocols that involve minimal sprint durations and repetitions.