Andrew Keech

Differential expression of muscle damage in humans following acute fast and slow velocity eccentric exercise

We sought to determine if the velocity of an acute bout of eccentric contractions influenced the duration and severity of several common indirect markers of muscle damage. Subjects performed 36 maximal fast (FST, n = 8: 3.14 rad x s(-1)) or slow (SLW, n = 7: 0.52 rad x s(-1)) velocity isokinetic eccentric contractions with the elbow flexors of the non-dominant arm. Muscle soreness, limb girth, plasma creatine kinase (CK) activity, isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad x s(-1) were assessed prior to and for several days following the eccentric bout. Peak plasma CK activity was similar in SLW (4030 +/- 1029 U x 1(-1)) and FST (5864 +/- 2664 U x 1(-1)) groups, (p > 0.05). Both groups experienced similar decrement in all strength variables during the 48 hr following the eccentric bout. However, recovery occurred more rapidly in the FST group during eccentric (0.52 and 3.14 rad x s(-1)) and concentric (3.14 rad x s(-1)) post-testing. The severity of muscle soreness was similar in both groups. However, the FST group experienced peak muscle soreness 48 hr later than the SLW group (24 hr vs. 72 hr). The SLW group experienced a greater increase in upper arm girth than the FST group 20 min, 24 hr and 96 hr following the eccentric exercise bout. The contraction velocity of an acute bout of eccentric exercise differentially influences the magnitude and time course of several indirect markers of muscle damage.

The effects of high‐intensity interval training vs. moderate‐intensity continuous training on body composition in overweight and obese adults: a systematic review and meta‐analysis

The objective of this study is to compare the effects of high‐intensity interval training (HIIT) and moderate‐intensity continuous training (MICT) for improvements in body composition in overweight and obese adults.

Intensity-dependent effects of aerobic training on pressure pain threshold in overweight men: A randomized trial

To investigate the chronic and acute effects of high‐intensity interval training (HIIT) and moderate‐intensity continuous training (MICT) on pressure pain thresholds (PPT) in overweight men.

Autonomic nervous system function, activity patterns, and sleep after physical or cognitive challenge in people with chronic fatigue syndrome

OBJECTIVE To explore changes in autonomic functioning, sleep, and physical activity during a post-exertional symptom exacerbation induced by physical or cognitive challenge in participants with chronic fatigue syndrome (CFS). METHODS Thirty-five participants with CFS reported fatigue levels 24-h before, immediately before, immediately after, and 24-h after the completion of previously characterised physical (stationary cycling) or cognitive (simulated driving) challenges. Participants also provided ratings of their sleep quality and sleep duration for the night before, and after, the challenge. Continuous ambulatory electrocardiography (ECG) and physical activity was recorded from 24-h prior, until 24-h after, the challenge. Heart rate (HR) and HR variability (HRV, as high frequency power in normalized units) was derived from the ECG trace for periods of wake and sleep. RESULTS Both physical and cognitive challenges induced an immediate exacerbation of the fatigue state (p<0.001), which remained elevated 24-h post-challenge. After completing the challenges, participants spent a greater proportion of wakeful hours lying down (p=0.024), but did not experience significant changes in sleep quality or sleep duration. Although the normal changes in HR and HRV during the transition from wakefulness to sleep were evident, the magnitude of the increase in HRV was significantly lower after completing the challenge (p=0.016). CONCLUSION Preliminary evidence of reduced nocturnal parasympathetic activity, and increased periods of inactivity, were found during post-exertional fatigue in a well-defined group of participants with CFS. Larger studies employing challenge paradigms are warranted to further explore the underlying pathophysiological mechanisms of post-exertional fatigue in CFS.

Reply to letter to the editor: high-intensity interval training vs. moderate-intensity continuous training: the lack of equalization, an ongoing problem: Letter to the Editor

We wish to thankMr Andreato and colleagues for their considered and insightful comments to our systematic review and meta-analysis. Our study focussed specifically on evaluating the relative merits of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) for improving body composition outcomes in overweight or obese, otherwise healthy individuals (1). We did not attempt to analyse each group’s effectiveness in relation to a non-exercising control group, nor analyse the training’s effectiveness in other populations (e.g. healthy normal weight individuals and chronic illness populations). We note that another recent meta-analysis published by Obesity Reviews has also compared the relative merits of these training programs but across a wider population base including healthy normal weight individuals, overweight and obese individuals and selected chronic illness populations (2). Both studies revealed broadly the same findings – HIIT and MICT appear to show similar, modest effectiveness for improving body fat levels. However, as Andreato and colleagues stated, it is important that we must be careful when interpreting these findings due to the need to stringently take into account studies that did not apply training protocols that were matched for total workload or oxygen consumption. We did not provide a sub-analysis comparing data from studies with matched protocols (N = 7 studies (3–9)) vs. unmatched protocols (N = 6 studies (10–15)) in our initial publication, and we agree this is a limitation. The unmatched studies invariably involved HIIT participants performing less total work than the MICT participants. We have since conducted a sub-analysis comparing our matched vs. unmatched studies. Our data show that our inclusion of six studies that involved unmatched training protocols for workload or oxygen consumption did not meaningfully influence the between-group standardized mean difference (SMD) comparisons (body mass – matched studies SMD = 0.06; unmatched studies SMD = 0.15; for body fat mass in kilograms – matched studies SMD = 0.07; unmatched studies SMD = 0.10, where positive numbers indicate a greater effect in MICT group compared with HIIT group). In contrast, while Keating et al. (2) report no significant differences in body composition outcomes between HIIT and MICT for studies involving matched protocols, the authors noted that HIIT protocols that involved lower time commitment or energy expenditure than MICT did tend to show less effectiveness for improving total body fat percentage (p = 0.09). There are two caveats to that point. Firstly, the finding was not supported for the measure of body fat mass in kilograms (p = 0.56). Secondly, matching groups by time commitment is problematic, because the main ‘selling’ point for wide-spread application of HIIT is its relative time-efficiency compared with MICT (16). Ideally, HIIT vs. MICT comparison studies need to involve less time commitment for the HIIT participants, with groups matched by total workload (Nm; easy to calculate in cycling studies) or, when workload cannot be accurately calculated (e.g. running studies), by total oxygen consumption (L O2). Matching groups by total energy expenditure, when total workload cannot be accurately calculated, is also flawed. For MICT sessions, an estimate of energy expenditure can be derived reasonably well, predominantly by applying a standard factor (typically 21 kilojoules per litre of O2 min 1 reflecting fat and carbohydrate oxidation rates) to the oxygen consumption values. This relationship is less accurate for HIIT sessions, and even less accurate again for sprint interval training, where a larger proportion of energy is drawn from glycolysis and ATP–PCr reactions. We also broadly agree with Andreato and colleagues that interpreting the clinical relevance of the data from our subanalysis comparing the effect of running and cycling studies on body composition is difficult due to the equalization issues that were raised. We reported a rather large effect of running training on body composition outcomes (SMD ~0.8) but not so for the cycling studies (SMD ~0.2), which was an intriguing finding. We appreciate Andreato and colleagues for noting that this is largely explained by the vast mismatch across the studies – the running studies appeared to involve much greater training volume than the cycling studies. Analysis of this data has shown that total exercise time for HIIT participants in running studies was 107% higher than in cycling studies (running: N = 6 studies, 1471 ± 1108 min vs. cycling: N = 7 studies, obesity reviews doi: 10.1111/obr.12586

Reply: High Intensity Interval versus Moderate Intensity Continuous Training in Patients with Coronary Artery Disease

We wish to thank Dr Cochrane for expressing an interest in our analysis of high intensity interval training (HIIT) versus moderate intensity continuous training (MICT) in patients with coronary artery disease (CAD) [1]. Our study [2] aimed to examine the relative merits of HIIT and MICT in these patients. We concluded that neither HIIT nor MICT has demonstrated clear superiority over the other, particularly in terms of patients’ long-term prognosis. We suggested that this was due to a lack of evidence in this domain, which is reflected by the current guidelines on secondary prevention, where level B and C evidence remain the sole basis for all current recommendations in this regard [3]. We reinforced this notion by indicating the need for large scale studies with mechanisms for long term follow-up, as similar studies (with follow-up up to 16 years) performed in healthy individuals have favoured vigorous over moderate intensity exercise in the prevention of CAD and improvement of the subjects’ risk factor profiles [4]. Further, HIIT has also been shown to have superior efficacy in improving vascular function in patients with a range of pre-existing cardiometabolic disorders [5]. While HIIT undertaken in isolationmay prove to be unsustainable over time for some, patients’ compliance with various exercise programs has not been thoroughly and comprehensively studied, nor have the factors that influence it. Logically, exercise regimens that are achievable with respect to patients’ age and underlying fitness are most likely to be continued. Indeed, instead of pitting one form of exercise against another, our study was really designed to differentiate and characterise them so that they can be tailored to the needs and physiological attributes of our patients in order to enhance their long-term adherence to the exercise programs. Finally, maximal aerobic capacity, often termed VO2max, remains a reasonable clinical and study endpoint in our