Effects of acute and chronic stair-climbing exercise on metabolic health: A systematic review.

Stair climbing exercise (SE) provides a feasible approach to elevate physical activity, but the effects on metabolic health are unclear. We systematically reviewed the currently available evidence on the effects of SE on fasting and postprandial glycaemia and lipidaemia. Studies were included if they investigated the effects of acute or chronic (at least 2 weeks) SE on fasting and/or postprandial glycaemic (insulin and glucose) and lipidaemic (triacylglycerols and non-esterified fatty acids) responses in healthy, prediabetic or type 2 diabetic adult populations. PubMed, Web of Science and Scopus were searched for eligible studies until July 2022. A total of 25 studies (14 acute and 11 chronic) were eligible for review. Acute bout(s) of SE can reduce postprandial glycaemia in individuals with prediabetes and type 2 diabetes (8 of 9 studies), but not in normoglycemic individuals. The effects of acute SE on postprandial lipidaemic responses and SE training on both fasting and postprandial glycaemia/lipidaemia were unclear. Acute SE may reduce postprandial glucose concentrations in people with impaired glycaemic control, but high-quality studies are needed. More studies are needed to determine the effect of chronic SE training on postprandial glucose and lipid responses, and the acute effects of SE on lipid responses.

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 HIT' (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.

Heterogeneous Treatment Effects after Inspiratory Muscle Training during Recovery from Postacute COVID-19 Syndrome.

PURPOSE: The objective of this study is to investigate whether heterogeneous treatment effects occur for changes in inspiratory muscle strength, perceived dyspnea, and health-related quality of life after 8 wk of unsupervised home-based inspiratory muscle training (IMT) in adults with postacute coronavirus disease 2019 (COVID-19) syndrome. METHODS: In total, 147 adults with self-reported prior COVID-19 either completed an 8-wk home-based IMT intervention ( n = 111, 92 females, 48 ± 11 yr, 9.3 ± 3.6 months postacute COVID-19 infection) or acted as "usual care" wait list controls ( n = 36, 34 females, 49 ± 12 yr, 9.4 ± 3.2 months postacute COVID-19 infection). RESULTS: Applying a Bayesian framework, we found clear evidence of heterogeneity of treatment response for inspiratory muscle strength: the estimated difference between standard deviations (SD) of the IMT and control groups was 22.8 cm H 2 O (75% credible interval (CrI), 4.7-37.7) for changes in maximal inspiratory pressure (MIP) and 86.8 pressure time units (75% CrI, 55.7-116.7) for sustained MIP (SMIP). Conversely, there were minimal differences in the SD between the IMT and the control group for changes in perceived dyspnea and health-related quality of life, providing no evidence of heterogeneous treatment effects. Higher cumulative power during the IMT intervention was related to changes in MIP ( ß = 10.9 cm H 2 O (95% CrI, 5.3-16.8) per 1 SD) and SMIP ( ß = 63.7 (32.2-95.3) pressure time units per 1 SD), clearly indicating an IMT dose response for changes in inspiratory muscle strength. Older age (>50 yr), a longer time postacute COVID-19 (>3 months), and greater severity of dyspnea at baseline were also associated with smaller improvements in inspiratory muscle strength. CONCLUSIONS: Heterogeneous individual responses occurred after an 8-wk home-based IMT program in people with postacute COVID-19 syndrome. Consistent with standard exercise theory, larger improvements in inspiratory muscle strength are strongly related to a greater cumulative dose of IMT.

Exploring interindividual differences in fasting and postprandial insulin sensitivity adaptations in response to sprint interval exercise training.

Previous studies have concluded that wide variance in changes in insulin sensitivity markers following exercise training demonstrates heterogeneity in individual trainability. However, these studies frequently don't account for technical, biological, and random within-subject measurement error. We used the standard deviation of individual responses (SDIR) to determine whether interindividual variability in trainability exists for fasting and postprandial insulin sensitivity outcomes following low-volume sprint interval training (SIT). We pooled data from 63 untrained participants who completed 6 weeks of SIT (n = 49; VO2max: 35 (7) mL⋅kg-1⋅min-1) or acted as no-intervention controls (n = 14; VO2max: 34 (6) mL⋅kg-1⋅min-1). Fasting and oral glucose tolerance test (OGTT)-derived measures of insulin sensitivity were measured pre- and post-intervention. SDIR values were positive and exceeded a small effect size threshold for changes in fasting glucose (SDIR = 0.27 [95%CI 0.07,0.38] mmol⋅L-1), 2-h OGTT glucose (SDIR = 0.89 [0.22,1.23] mmol⋅L-1), glucose area-under-the-curve (SDIR = 66.4 [-81.5,124.3] mmol⋅L-1⋅120min-1) and The Cederholm Index (SDIR = 7.2 [-16.0,19.0] mg⋅l2⋅mmol-1⋅mU-1⋅min-1), suggesting meaningful individual responses to SIT, whilst SDIR values were negative for fasting insulin, fasting insulin resistance and insulin AUC. For all variables, the 95% CIs were wide and/or crossed zero, highlighting uncertainty about the existence of true interindividual differences in exercise trainability. Only 2-22% of participants could be classified as responders or non-responders with more than 95% certainty. Our findings demonstrate it cannot be assumed that variation in changes in insulin sensitivity following SIT is attributable to inherent differences in trainability, and reiterate the importance of accounting for technical, biological, and random error when examining heterogeneity in health-related training adaptations.Highlights This study tested whether true interindividual variability exists for changes in insulin sensitivity and glyceamic control following 6-weeks of low volume sprint interval training (SIT).The high level of technical, biological, and random error associated with repeated measurements of insulin sensitivity and glycaemic control, means we can neither confidently conclude that there is evidence of true interindividual differences in the trainability of these outcomes following SIT, nor confidently identify responders or non-responders for such parameters.Researchers contrasting responders vs. non-responders for a given parameter, either to understand mechanisms of adaptation and/or develop physiological/genetic/epigenetic predictors of response, need to be aware that identification of responders and non-responders with sufficient certainty may not be achievable for parameters with a high level of technical, biological, and random error.

Ecological inference using data from accelerometers needs careful protocols.

Accelerometers in animal-attached tags are powerful tools in behavioural ecology, they can be used to determine behaviour and provide proxies for movement-based energy expenditure. Researchers are collecting and archiving data across systems, seasons and device types. However, using data repositories to draw ecological inference requires a good understanding of the error introduced according to sensor type and position on the study animal and protocols for error assessment and minimisation.Using laboratory trials, we examine the absolute accuracy of tri-axial accelerometers and determine how inaccuracies impact measurements of dynamic body acceleration (DBA), a proxy for energy expenditure, in human participants. We then examine how tag type and placement affect the acceleration signal in birds, using pigeons Columba livia flying in a wind tunnel, with tags mounted simultaneously in two positions, and back- and tail-mounted tags deployed on wild kittiwakes Rissa tridactyla. Finally, we present a case study where two generations of tag were deployed using different attachment procedures on red-tailed tropicbirds Phaethon rubricauda foraging in different seasons.Bench tests showed that individual acceleration axes required a two-level correction to eliminate measurement error. This resulted in DBA differences of up to 5% between calibrated and uncalibrated tags for humans walking at a range of speeds. Device position was associated with greater variation in DBA, with upper and lower back-mounted tags varying by 9% in pigeons, and tail- and back-mounted tags varying by 13% in kittiwakes. The tropicbird study highlighted the difficulties of attributing changes in signal amplitude to a single factor when confounding influences tend to covary, as DBA varied by 25% between seasons.Accelerometer accuracy, tag placement and attachment critically affect the signal amplitude and thereby the ability of the system to detect biologically meaningful phenomena. We propose a simple method to calibrate accelerometers that can be executed under field conditions. This should be used prior to deployments and archived with resulting data. We also suggest a way that researchers can assess accuracy in previously collected data, and caution that variable tag placement and attachment can increase sensor noise and even generate trends that have no biological meaning.

Affecting Effects on Affect: The Impact of Protocol Permutations on Affective Responses to Sprint Interval Exercise; A Systematic Review and Meta-Analysis of Pooled Individual Participant Data.

Responses to sprint interval exercise (SIE) are hypothesized to be perceived as unpleasant, but SIE protocols are diverse, and moderating effects of various SIE protocol parameters on affective responses are unknown. We performed a systematic search to identify studies (up to 01/05/2021) measuring affective valence using the Feeling Scale during acute SIE in healthy adults. Thirteen studies involving 18 unique trials and 316 unique participant (142 women and 174 men) affective responses to SIE were eligible for inclusion. We received individual participant data for all participants from all studies. All available end-of-sprint affect scores from each trial were combined in a linear mixed model with sprint duration, mode, intensity, recovery duration, familiarization and baseline affect included as covariates. Affective valence decreased significantly and proportionally with each additional sprint repetition, but this effect was modified by sprint duration: affect decreased more during 30 s (0.84 units/sprint; 95% CI: 0.74-0.93) and 15-20 s sprints (1.02 units/sprint; 95% CI: 0.93-1.10) compared with 5-6 s sprints (0.20 units/sprint; 95% CI: 0.18-0.22) (both p < 0.0001). Although the difference between 15-20 s and 30 s sprints was also significant (p = 0.02), the effect size was trivial (d = -0.12). We observed significant but trivial effects of mode, sprint intensity and pre-trial familiarization, whilst there was no significant effect of recovery duration. We conclude that affective valence declines during SIE, but the magnitude of the decrease for an overall SIE session strongly depends on the number and duration of sprints. This information can be applied by researchers to design SIE protocols that are less likely to be perceived as unpleasant in studies of real-world effectiveness. SYSTEMATIC REVIEW REGISTRATION: Open Science Framework, https://osf.io/sbyn3.

Anti-carcinogenic effects of exercise-conditioned human serum: evidence, relevance and opportunities.

Regular physical activity reduces the risk of several site-specific cancers in humans and suppresses tumour growth in animal models. The mechanisms through which exercise reduces tumour growth remain incompletely understood, but an intriguing and accumulating body of evidence suggests that the incubation of cancer cells with post-exercise serum can have powerful effects on key hallmarks of cancer cell behaviour in vitro. This suggests that exercise can impact tumour biology through direct changes in circulating proteins, RNA molecules and metabolites. Here, we provide a comprehensive narrative overview of what is known about the effects of exercise-conditioned sera on in vitro cancer cell behaviour. In doing so, we consider the key limitations of the current body of literature, both from the perspective of exercise physiology and cancer biology, and we discuss the potential in vivo physiological relevance of these findings. We propose key opportunities for future research in an area that has the potential to identify key anti-oncogenic protein targets and optimise physical activity recommendations for cancer prevention, treatment and survivorship.

Heterogeneity and incidence of non-response for changes in cardiorespiratory fitness following time-efficient sprint interval exercise training.

Interindividual variability for training-induced changes in maximal oxygen uptake (V̇O2max) is well described following continuous aerobic and high-intensity interval training. Whether similar variability is observed following time-efficient sprint interval training with minimal training volume (i.e., reduced-exertion high-intensity interval training; REHIT) is unknown. We conducted a pooled analysis of n = 117 (68 men) training participants (mean ± SD: age: 30 ± 10 y; V̇O2max: 34.8 ± 7.5 mL·kg-1·min-1), who completed a V̇O2max assessment before and 3 days after 6 weeks of REHIT comprising of two 10-20-s 'all-out' cycling sprints per session, and n = 40 no-intervention control participants (age: 30 ± 13 y; V̇O2max: 31.5 ± 6.5 mL·kg-1·min-1) who completed repeated V̇O2max tests over a comparable timeframe. Individual responses estimated using 50% confidence intervals derived from the technical error were interpreted against a smallest worthwhile change of 1.75 mL·kg-1·min-1. The standard deviation of individual responses was 2.39 mL·kg-1·min-1 demonstrating clinically meaningful heterogeneity in training-induced changes in V̇O2max following REHIT that exceed the technical, biological and random within-subjects variability of V̇O2max assessment. The likely (75% probability) non-response rate was 18% (21/117), and 49% (57/117) of individuals demonstrated increases in V̇O2max likely higher than the smallest worthwhile change. We conclude that the well-described increase in V̇O2max following REHIT at the group level is subject to substantial variability in magnitude at an individual level. This has important implications for exercise prescription and can be harnessed to elucidate mechanisms of adaptation. Novelty: There is substantial heterogeneity in V̇O2max responses following time-efficient sprint interval training. Proportion of non-response was 18% and ∽50% of individuals show clinically meaningful increases in V̇O2max.

Omission of a carbohydrate-rich breakfast impairs evening endurance exercise performance despite complete dietary compensation at lunch.

Omission of a carbohydrate-rich breakfast followed by consuming an ad libitum lunch impairs evening exercise performance. However, it is unclear if this is due to breakfast omission per se, or secondary to lower carbohydrate intake over the day. To test whether impaired evening performance following breakfast omission persists when complete dietary compensation occurs at lunch, in a randomised cross-over design, eleven highly trained cyclists (age: 25 ± 7 y, VO2max: 61 ± 5 ml·kg-1·min-1) completed two trials: breakfast (B) and no breakfast (NB). During B, participants consumed an individualised breakfast (583 ± 54 kcal; 8-9am) and lunch (874 ± 80 kcal; 12-2pm), whilst during NB participants fasted until 12pm and then consumed a standardised lunch (1457 ± 134 kcal: 12-2pm). The overall energy (1457 ± 134 kcal) and macronutrient profile (carbohydrate: 81.5 ± 0.4%, fat: 5.8 ± 0.1%, protein: 12.7 ± 0.3%) was identical in both trials, with timing the only difference. Mean power output during a 20 km time trial performed in the evening was ~3% lower in NB compared to B (mean difference [95% CI]: -9.1 [-15.3, -2.9] watts, p < 0.01 for condition main effect). No differences in heart rate, blood glucose or blood lactate concentrations were apparent, but perception of effort appeared to be higher in the early stages of the time trial in NB compared to B despite lower power output. Impaired high-intensity endurance performance in the evening following breakfast omission is related to meal timing rather than carbohydrate intake / availability. Provision of an early morning high-carbohydrate meal should be considered to optimise evening exercise performance.

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).

Reducing training frequency from 3 or 4 sessions/week to 2 sessions/week does not attenuate improvements in maximal aerobic capacity with reduced-exertion high-intensity interval training (REHIT).

In the present randomised-controlled trial we investigated the effect of reduced-exertion high-intensity interval training (REHIT) training frequency (2, 3, or 4 sessions/week for 6 weeks) on maximal aerobic capacity in 42 inactive individuals (13 women; mean ± SD age: 25 ± 5 years, maximal aerobic capacity: 35 ± 5 mL·kg-1·min-1). Changes in maximal aerobic capacity were not significantly different between the 3 groups (2 sessions/week: +10.2%; 3 sessions/week: +8.1%; 4 sessions per week: +7.3%). In conclusion, a training frequency of 2 sessions/week is sufficient for REHIT to improve maximal aerobic capacity. Novelty We demonstrate that reducing REHIT training frequency from 3 or 4 to 2 sessions/week does not attenuate improvements in the key health marker of maximal aerobic capacity.

Extremely short duration interval exercise improves 24-h glycaemia in men with type 2 diabetes.

PURPOSE: Reduced-exertion high-intensity interval training (REHIT) is a genuinely time-efficient exercise intervention that improves aerobic capacity and blood pressure in men with type 2 diabetes. However, the acute effects of REHIT on 24-h glycaemia have not been examined. METHODS: 11 men with type 2 diabetes (mean ± SD: age, 52 ± 6 years; BMI, 29.7 ± 3.1 kg/m2; HbA1c, 7.0 ± 0.8%) participated in a randomised, four-trial crossover study, with continual interstitial glucose measurements captured during a 24-h dietary-standardised period following either (1) no exercise (CON); (2) 30 min of continuous exercise (MICT); (3) 10 × 1 min at ~ 90 HRmax (HIIT; time commitment, ~ 25 min); and (4) 2 × 20 s 'all-out' sprints (REHIT; time commitment, 10 min). RESULTS: Compared to CON, mean 24-h glucose was lower following REHIT (mean ± 95%CI: - 0.58 ± 0.41 mmol/L, p = 0.008, d = 0.55) and tended to be lower with MICT (- 0.37 ± 0.41 mmol/L, p = 0.08, d = 0.35), but was not significantly altered following HIIT (- 0.37 ± 0.59 mmol/L, p = 0.31, d = 0.35). This seemed to be largely driven by a lower glycaemic response (area under the curve) to dinner following both REHIT and MICT (- 11%, p < 0.05 and d > 0.9 for both) but not HIIT (- 4%, p = 0.22, d = 0.38). Time in hyperglycaemia appeared to be reduced with all three exercise conditions compared with CON (REHIT: - 112 ± 63 min, p = 0.002, d = 0.50; MICT: -115 ± 127 min, p = 0.08, d = 0.50; HIIT - 125 ± 122 min, p = 0.04, d = 0.54), whilst indices of glycaemic variability were not significantly altered. CONCLUSION: REHIT may offer a genuinely time-efficient exercise option for improving 24-h glycaemia in men with type 2 diabetes and warrants further study.

What can knowledge of the energy landscape tell us about animal movement trajectories and space use? A case study with humans.

Recent work has highlighted that 'energy landscapes' should affect animal movement trajectories although expected patterns are rarely quantified. We developed a model, incorporating speed, substrate, superstrate and terrain slope, to determine minimized movement costs for an energetically well-understood model animal, Homo sapiens, negotiating an urban environment, to highlight features that promote increased tortuosity and affect area use. The model showed that high differential travel power costs between adjacent areas, stemming from substantial environmental heterogeneity in the energy landscape, produced the most tortuous least-cost paths across scales. In addition, projected territory size and shape in territorial animals is likely to be affected by the details in the energy landscape. We suggest that cognisance of energy landscapes is important for understanding animal movement patterns and that energetic differences between least cost- and observed pathways might code for, and give an explicit value to, other important landscape-use factors, such as the landscape of fear, food availability or social effects.

Decreasing sprint duration from 20 to 10 s during reduced-exertion high-intensity interval training (REHIT) attenuates the increase in maximal aerobic capacity but has no effect on affective and perceptual responses.

Recent studies have demonstrated that modifying the "classic" 6 × 30-s "all-out" sprint interval training protocol by incorporating either shorter sprints (6 × 10-s or 15-s sprints) or fewer sprints (e.g., 2 × 20-s sprints; reduced-exertion high-intensity interval training (REHIT)) does not attenuate the training-induced improvements in maximal aerobic capacity. The aim of the present study was to determine if reducing the sprint duration in the REHIT protocol from 20 s to 10 s per sprint influences acute affective responses and the change in maximal aerobic capacity following training. Thirty-six sedentary or recreationally active participants (17 women; mean ± SD; age: 22 ± 3 years; body mass index: 24.5 ± 4.6 kg·m-2; maximal aerobic capacity: 37 ± 8 mL·kg-1·min-1) were randomised to a group performing a "standard" REHIT protocol involving 2 × 20-s sprints or a group who performed 2 × 10-s sprints. Maximal aerobic capacity was determined before and after 6 weeks of 3 weekly training sessions. Acute affective responses and perceived exertion were assessed during training. Greater increases in maximal aerobic capacity were observed for the group performing 20-s sprints (2.77 ± 0.75 to 3.04 ± 0.75 L·min-1; +10%) compared with the group performing 10-s sprints (2.58 ± 0.57 vs. 2.67 ± 3.04 L·min-1; +4%; group × time interaction effect: p < 0.05; d = 1.06). Positive affect and the mood state vigour increased postexercise, while tension, depression, and total mood disturbance decreased, and negative affect remained unchanged. Affective responses and perceived exertion were not altered by training and were not different between groups. In conclusion, reducing sprint duration in the REHIT protocol from 20 s to 10 s attenuates improvements in maximal aerobic capacity, and does not result in more positive affective responses or lower perceived exertion.

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.