The association between time-of-day of habitual exercise training and changes in relevant cancer health outcomes among cancer survivors

Objective To assess the relationship between time-of-day of exercise training and changes in relevant cancer health outcomes among cancer survivors. Methods Retrospective analysis of data collected from 2016–2019 from a hospital-based exercise oncology program. Descriptive statistics were calculated for demographic, clinical, and exercise timing characteristics (e.g. AM, PM, or mix) among survivors with available data for exercise training time (n = 233). For the total sample and a breast cancer sub-analysis, univariate analysis of covariance, adjusted for age, was carried out by exercise training time, for change in the following outcomes collected during the program’s assessment sessions: cardiorespiratory fitness and muscular endurance (human performance variables), physical function, anthropometrics, self-reported fatigue, and quality of life (QoL). Change in body mass index (BMI) and body weight was included in the breast cancer analysis. Results Overall, 37.3% of survivors habitually engaged in AM exercise (e.g. ≥ 75% AM training), 34.3% in PM exercise, and 28.3% in a mix of AM and PM exercise training throughout the program. Median time in the program was 17 weeks. Significant improvements in most human performance and physical function variables were observed in the total sample regardless of exercise training time-of-day. Among breast cancer survivors, PM but not AM or mixed was associated with improvements in fitness, and lower-body muscular endurance and function. Mixed exercise timing was linked with greater increase in waist circumference (total sample: 3.02cm, 95%CI 1.55, 4.49; breast cancer: 3.57cm 95%CI 0.96, 6.18), body weight (breast cancer: 1.6kg, 95%CI 0.3, 2.8) and BMI (breast cancer: 0.6kg/m2, 95%CI 0.1, 1.0). AM and PM exercise, but not mixed, was associated with improvements in fatigue and QoL. Conclusion Time-of-day of exercise training may differentially impact changes in human performance and physical function variables. Mixed exercise training time may result in less favorable outcomes related of weight management variables among cancer survivors.

Timing of Creatine Supplementation around Exercise: A Real Concern?

Creatine has been considered an effective ergogenic aid for several decades; it can help athletes engaged in a variety of sports and obtain performance gains. Creatine supplementation increases muscle creatine stores; several factors have been identified that may modify the intramuscular increase and subsequent performance benefits, including baseline muscle Cr content, type II muscle fibre content and size, habitual dietary intake of Cr, aging, and exercise. Timing of creatine supplementation in relation to exercise has recently been proposed as an important consideration to optimise muscle loading and performance gains, although current consensus is lacking regarding the ideal ingestion time. Research has shifted towards comparing creatine supplementation strategies pre-, during-, or post-exercise. Emerging evidence suggests greater benefits when creatine is consumed after exercise compared to pre-exercise, although methodological limitations currently preclude solid conclusions. Furthermore, physiological and mechanistic data are lacking, in regard to claims that the timing of creatine supplementation around exercise moderates gains in muscle creatine and exercise performance. This review discusses novel scientific evidence on the timing of creatine intake, the possible mechanisms that may be involved, and whether the timing of creatine supplementation around exercise is truly a real concern.

The Effect of Exercise Timing on Elevated Postprandial Glucose in Women With Obesity

Background and Aim: This study aimed to investigate the effect of exercise timing on elevated postprandial glucose and after brief interval exercises in women with obesity. Methods & Materials: Ten women with obesity (Mean±SD age = 40.41±3.97 years; weight = 86.66±7.26 kg; and BMI = 33.22±2.20 kg/m2) participated in a crossover design exercise intervention: 1) postprandial aerobic exercise, 2) pre-prandial aerobic exercise, 3) brief periodic exercise, and 4) control. Pre- and postprandial exercise included 30 min of moderate-intensity walking on the treadmill before and after each main meal (1 minute of exercise -30 seconds rest). The brief periodic exercise had three one-minute reps of activity every 30 min for 20 times during the day. Twelve-hour continuous glucose monitoring and two-hour postprandial glucose levels were calculated to examine changes in blood glucose levels. Ethical Considerations: This study was approved by the institutional review board of the University of Isfahan (Ethics Code: IR.UI.REC.1397.119) and conducted in agreement with the ethical principles for biomedical research involving human subjects outlined in the declaration of Helsinki. Results: The findings of this study suggested that brief periodic exercise resulted in a significant decrease in continuous glucose monitoring levels and postprandial glucose compared to the control group as well as pre-prandial exercise (P˂0.05). However, pre- and postprandial exercise did not result in significant changes in continuous glucose monitoring (P˃0.05). In addition, postprandial exercise led to a significant decrease in postprandial glucose compared to the control group (P˂0.05). Conclusion: It seems that brief periodic exercise can have more beneficial effects on postprandial glucose levels, probably due to improved glucose metabolism in skeletal muscle.

Examining the Role of Exercise Timing in Weight Management: A Review

Many adults cite exercise as a primary strategy for losing weight, yet exercise alone is modestly effective for weight loss and results in variable weight loss responses. It is possible that some of the variability in weight loss may be explained by the time of day that exercise is performed. Few studies have directly compared the effects of exercise performed at different times of the day (i. e., morning versus evening exercise). Results from these existing studies are mixed with some studies demonstrating superior weight and fat mass loss from morning exercise, while other studies have found that evening exercise may be better for weight management. Exercise timing may alter modifiable lifestyle behaviors involved in weight management, such as non-exercise physical activity, energy intake, and sleep. The purpose of this review is to summarize evidence for and against time-of-day dependent effects of exercise on weight management. Although limited, we also review studies that have examined the effect of exercise timing on other lifestyle behaviors linked to body weight regulation. While exercise at any time of day is beneficial for health, understanding whether there is an optimal time of day to exercise may advance personalized treatment paradigms for weight management.

Eat, Train, Sleep—Retreat? Hormonal Interactions of Intermittent Fasting, Exercise and Circadian Rhythm

The circadian rhythmicity of endogenous metabolic and hormonal processes is controlled by a complex system of central and peripheral pacemakers, influenced by exogenous factors like light/dark-cycles, nutrition and exercise timing. There is evidence that alterations in this system may be involved in the pathogenesis of metabolic diseases. It has been shown that disruptions to normal diurnal rhythms lead to drastic changes in circadian processes, as often seen in modern society due to excessive exposure to unnatural light sources. Out of that, research has focused on time-restricted feeding and exercise, as both seem to be able to reset disruptions in circadian pacemakers. Based on these results and personal physical goals, optimal time periods for food intake and exercise have been identified. This review shows that appropriate nutrition and exercise timing are powerful tools to support, rather than not disturb, the circadian rhythm and potentially contribute to the prevention of metabolic diseases. Nevertheless, both lifestyle interventions are unable to address the real issue: the misalignment of our biological with our social time.

The Impact of Acute Exercise Timing on Memory Interference

This study evaluated whether the timing of acute exercise can attenuate a memory interference effect. Across two experiments, participants completed an AB/AC memory task. Participants studied eight word pairs; four denoted AB (e.g., Hero – Apple) and four control (DE) pairs. Following this List 1, participants studied eight additional word pairs (List 2); four denoted AC, re-using words from the AB pairs (e.g., Hero – Project) and four control (FG) pairs. Following their study of both lists, participants completed a cued recall assessment. In Experiment 1 (N = 100), an acute exercise bout occurred before the AB/AC memory interference task, and the participants’ three lab visits (successive conditions) were control, moderate-intensity (50% HRR; heart rate reserve) exercise, and vigorous-intensity (80% HRR) exercise. In Experiment 2 (N = 68), the acute exercise occurred between List 1 and List 2, and the participants’ two lab visits (successive conditions) were a (80% HRR) vigorous-intensity exercise visit and a control visit. Across both experiments, we observed evidence of both proactive and retroactive interference ( p < .05), but acute exercise, regardless of intensity, did not attenuate this interference ( p > .05). Acute moderate-intensity exercise was better than control or vigorous-intensity exercise in enhancing associative memory ( p < .05), independent of interference. In Experiment 2, vigorous intensity exercise was associated with more pronounced interference ( p < .05). Our results suggest that acute exercise can enhance associative memory performance, with no attenuation of interference by exercise.

Sustaining Regular Exercise During Weight Loss Maintenance: The Role of Consistent Exercise Timing

Background: Exercising at a consistent versus variable time of day cross-sectionally relates to greater moderate to vigorous physical activity (MVPA) among weight loss maintainers. This study evaluated the relationships between exercise timing and both MVPA levels and habit strength, as well as stability in exercise timing, over 1 year among maintainers in the National Weight Control Registry. Methods: Participants (n = 709) completed questionnaires assessing exercise timing, MVPA, and exercise automaticity (a measure of habit) at baseline and 1-year follow-up. At each assessment, participants were labeled temporally consistent exercisers if >50% of their exercise sessions per week occurred in one time window: early morning, late morning, afternoon, or evening. Participants exercising consistently during the same window at both assessments were labeled as having stable patterns. Results: Temporally consistent exercise at baseline, regardless of its specific time, related to greater MVPA over time (Ps< .05). Approximately half of temporally consistent exercisers at baseline exhibited stable patterns. Early morning exercise and greater exercise automaticity at baseline predicted stable patterns (Ps< .005). Temporally consistent exercise, especially during the early morning, related to greater automaticity across time (Ps< .01). Conclusions: Consistent exercise timing may help maintainers accrue more MVPA. Consistent early morning exercise was most strongly related to exercise automaticity and routine stability.

Effects of Exercise on Explicit Memory Function: Incidental and Intentional Encoding May Depend on Exercise Timing

The present experiment evaluated the effects of self-reported exercise behavior and an acute bout of high-intensity exercise on explicit memory function. The memory tasks were encoded either incidentally or intentionally; for intentional encoding, participants were told to focus on memorizing the stimuli (words), whereas for incidental encoding, participants were unaware that they would be subsequently asked to complete an object recognition task. Among a sample of 150 adults (Mage = 20 years), randomly assigned experimental participants engaged in the following task sequence: (a) incidentally encoded a series of objects, (b) engaged in 20 minutes of high-intensity exercise, (c) intentionally encoded a word list, and (d) completed explicit memory retrieval tasks. Control group participants viewed a time matched video in lieu of high intensity exercise. We measured self-reported exercise behavior via an exercise questionnaire. We did not observe convincing evidence of an effect of high-intensity acute exercise, when occurring during the early consolidation period, on memory function, for either incidental or intentional encoding tasks. However, self-reported engagement in moderate-to-vigorous physical activity was favorably associated with explicit memory performance.