Effect of ice slurry ingestion on thermoregulatory responses during fixed-intensity cycling in humid and dry heat.

PURPOSE: This study examined the thermoregulatory response and ergogenic effects of ice slurry (ICE) ingestion in hot environments with high and low relative humidity (RH). METHODS: Eight males completed four trials in a crossover manner in dry (DRY: 34.7 ± 0.2 °C, 38 ± 2%RH) and humid heat (HUM: 34.8 °C ± 0.2 °C, 80 ± 1%RH). They ingested 8.0 g·kg-1 of ICE (0.0 °C) or 37.5 °C water (CON) during 30 min before exercise, and three aliquots (3.2 g·kg-1) of ICE or CON during 45-min cycling at 50%[Formula: see text]O2peak, followed by cycling to exhaustion at 80%[Formula: see text]O2peak (TTE). Body core temperature (Tcore), mean skin temperature (Tsk), heart rate (HR), thermal comfort, thermal sensation and rating of perceived exertion (RPE) were measured. RESULTS: Relative to CON, ICE improved TTE by 76.5 ± 96.5% in HUM and 21.3 ± 44.9% in DRY (p = 0.044). End-exercise Tcore was lower in ICE versus CON in DRY (37.8 ± 0.4 °C versus 38.1 ± 0.3 °C, p = 0.005) and HUM (38.8 ± 0.4 °C versus 39.3 ± 0.6 °C, p = 0.004). ICE decreased HR, heat storage and heat strain index only in DRY (p < 0.001-0.018). ICE improved thermal sensation and comfort in DRY and HUM (p < 0.001-0.011), attenuated RPE in HUM (p = 0.012) but not in DRY (p = 0.065). CONCLUSION: ICE tended to benefit performance in humid heat more than in dry heat. This is likely due to the reduced extent of hyperthermia in dry heat and the relative importance of sensory inputs in mediating exercise capacity.

Weekday breakfast habits and mood at the start of the school morning.

BACKGROUND: Good nutrition, regular physical activity, and adequate sleep are important for promoting health. However, it is not well characterized how these lifestyle behaviours are associated with mood at the start of school days. AIM: To identify the weekday health-related behaviours (breakfast intake, physical activity, and sleep) of Singaporean adolescents and explore their associations with mood at the beginning of the school morning. METHODS: 365 adolescents (52.3% boys, 47.7% girls) aged 14-19 years (M = 16.9, SD = 1.3 years) completed a survey set on breakfast habits, physical activity participation, sleep duration, and mood. RESULTS: More than one-third (38.6%) of participants never (15.0%) or irregularly (23.6%) consumed breakfast on weekdays. Adolescents consuming breakfast irregularly reported significantly higher negative mood scores than regular breakfast consumers (p = .002; d = .404). Almost two-thirds (64.1%) of adolescents did <60 min of moderate-to-vigorous physical activity (MVPA) on weekdays and reported lower positive morning mood scores than those who ≥60 min of MVPA (p = .014; d = .284). Although most (88.3%) adolescents slept <8 h each night, sleep duration was not related to either positive mood or negative mood. CONCLUSION: The present study suggests that eating breakfast on a regular basis and completing for ≥60 min of weekday MVPA are useful behaviours to start school days in a better mood. Parents and health educators should recognise the importance of establishing these habits and support students by instigating practical approaches so they can achieve a regular breakfast intake and physical activity engagement.

Energy replacement using glucose does not increase postprandial lipemia after moderate intensity exercise.

BACKGROUND: Aerobic exercise can decrease postprandial triglyceride (TG) concentrations but the relationship between exercise-induced energy deficits and postprandial lipemia is still unclear. The aim of the present study was to examine the effect of a single bout of aerobic exercise, with and without energy replacement, on postprandial lipemia and on peripheral blood mononuclear cell (PBMC) mRNA expression of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) receptors and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). METHODS: Nine healthy male humans completed three two-day trials in a random order. On day 1, volunteers rested (CON), completed 60 minutes of treadmill walking at 50% of VO2peak (EX) or completed the same bout of walking but with the energy replaced afterwards with a glucose solution (EXG). On day 2, volunteers rested and consumed a high fat test meal in the morning. RESULTS: Total and incremental TG AUC were significantly lower on the EXG (P < 0.05) and EX (P < 0.05) trials than the CON trial with no difference between the two exercise trials. No significant difference was observed in VLDL or LDL receptor mRNA expression among the trials (P > 0.05). CONCLUSIONS: In conclusion, energy replacement by glucose did not affect the decrease in postprandial TG concentrations observed after moderate intensity exercise and exercise does not affect changes in PBMC HMGCR, VLDL and LDL receptor mRNA expression.

Developing Nutrition Knowledge and Attitude Measures for Athletes With the Knowledge-Attitude-Behavior Model.

Purpose: Nutrition education programmes are often created to improve dietary intake in athletes. Unfortunately, the inconsistent link between nutrition knowledge and dietary behavior suggests that nutrition knowledge may not be a key influencer of dietary behavior. The Knowledge-Attitude-Behavior (KAB) model has been used in nutrition education although studies that evaluated this model were largely compromised by poorly constructed instruments and methodological discrepancies. Method: To improve understanding of the model, a Nutrition Knowledge Questionnaire (NKQ) and Athlete's Perspective on Nutrition (APN) instrument was developed using the theory of planned behavior as its theoretical framework. Validity and reliability were examined for 193 Sports Science students and 11 elite netballers. Content and face validity of the 48-item NKQ was confirmed by expert sport dietitians. Discriminant validity of the NKQ and factorial validity of the APN was established. Both instruments demonstrated acceptable internal consistency and good test-retest reliability. The final instruments were administered to elite athletes in a pilot study to understand the KAB model. Results: Correlation between nutrition knowledge and dietary behavior was significant (r = .811, p = .01). Nutrition knowledge was a positive predictor of netballers' dietary behavior (ß = .8, t(2) = 3.899, p = .005) but attitude was not (ß = -.097, t(2) = -.471, p = .65). Conclusion: Two psychometrically sound instruments developed in this study can be used to measure nutrition knowledge and attitude in an Asian group of athletes. The pilot study with athletes showed that nutrition knowledge predicted dietary behavior.

Enhanced far infrared emissivity, UV protection and near-infrared shielding of polypropylene composites via incorporation of natural mineral for functional fabric development.

Far infrared radiation in the range of 4-20 µm has been showed to have biological and health benefits to the human body. Therefore, incorporating far-infrared emissivity additives into polymers and/or fabrics hold promise for the development of functional textiles. In this study, we incorporated nine types of natural minerals into polypropylene (PP) film and examined their properties to identify potential candidates for functional textiles and apparels. The addition of 2% mineral powders into PP film increased the far-infrared emissivity (5-14 µm) by 7.65%-14.48%. The improvement in far-infrared emissivity within the range of 5-14 µm, which overlaps with the peak range of human skin radiation at 8-14 µm, results in increased absorption efficiency, and have the potential to enhance thermal and biological effects. Moreover, the incorporation of mineral powders in PP films exhibited favorable ultraviolet (UV) protection and near-infrared (NIR) shielding properties. Two films, specifically those containing red ochre and hematite, demonstrated excellent UV protection with a UPF rating of 50+ and blocked 99.92% and 98.73% of UV radiation, respectively. Additionally, they showed 95.2% and 93.2% NIR shielding properties, compared to 54.1% NIR shielding properties of PP blank films. The UV protection and NIR shielding properties offered additional advantages for the utilization of polymer composite with additives in the development of sportswear and other outdoor garments. The incorporation of minerals could absorb near-IR radiation and re-emit them at longer wavelength in the mid-IR region. Furthermore, the incorporation of minerals significantly improved the heat retention of PP films under same heat radiation treatment. Notably, films with red ochre and hematite exhibited a dramatic temperature increase, reaching 2.5 and 3.2 times the temperature increase of PP films under same heat radiation treatment, respectively (46.8 °C and 59.9 °C higher than the temperature increase of 20.9 °C in the PP film). Films with additives also demonstrated lower thermal effusivity than PP blank films, indicating superior heat insulation properties. Therefore, polypropylene films with mineral additives, particularly those containing red ochre and hematite, showed remarkable heat capacity, UV-protection, NIR-shielding properties and enhanced far infrared emissivity, making them promising candidates for the development of functional textiles.

Cardiorespiratory fitness and fat oxidation during exercise in Chinese, Indian, and Malay men with elevated body mass index.

A cross-sectional pilot investigation was performed in Chinese, Indian, and Malay men (15 each) with elevated body mass index to compare (i) cardiorespiratory fitness (CRF) and (ii) fat oxidation at rest and maximal fat oxidation during exercise. Predicted CRF (Chinese: 37.0 (5.1) mL·kg-1·min-1; Indian: 34.8 (5.6) mL·kg-1·min-1; Malay: 33.0 (7.1) mL·kg-1·min-1; P = 0.208) and resting fat oxidation were similar among groups. Maximal fat oxidation during exercise was lower in Indian (3.81 (1.02) mg·kg-1·min-1, P = 0.004) and Malay (3.36 (0.95) mg·kg-1·min-1, P < 0.001) than Chinese (5.17 (1.23) mg·kg-1·min-1) men. Fat oxidation during exercise may contribute toward obesity risk in Asian populations. ClinicalTrials.gov Identifier: NCT05337111.

Acute and Chronic Effects of Blood Flow Restricted High-Intensity Interval Training: A Systematic Review.

BACKGROUND: The implementation of blood flow restriction (BFR) during exercise is becoming an increasingly useful adjunct method in both athletic and rehabilitative settings. Advantages in pairing BFR with training can be observed in two scenarios: (1) training at lower absolute intensities (e.g. walking) elicits adaptations akin to high-intensity sessions (e.g. running intervals); (2) when performing exercise at moderate to high intensities, higher physiological stimulus may be attained, leading to larger improvements in aerobic, anaerobic, and muscular parameters. The former has been well documented in recent systematic reviews, but consensus on BFR (concomitant or post-exercise) combined with high-intensity interval training (HIIT) protocols is not well established. Therefore, this systematic review evaluates the acute and chronic effects of BFR + HIIT. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to identify relevant studies. A systematic search on 1 February 2022, was conducted on four key databases: ScienceDirect, PubMed, Scopus and SPORTDiscus. Quality of each individual study was assessed using the Physiotherapy Evidence Database (PEDro) scale. Extraction of data from included studies was conducted using an adapted version of the 'Population, Intervention, Comparison, Outcome' (PICO) framework. RESULTS: A total of 208 articles were identified, 18 of which met inclusion criteria. Of the 18 BFR + HIIT studies (244 subjects), 1 reported both acute and chronic effects, 5 examined acute responses and 12 investigated chronic effects. Acutely, BFR challenges the metabolic processes (vascular and oxygenation responses) during high-intensity repeated sprint exercise-which accelerates central and peripheral neuromuscular fatigue mechanisms resulting in performance impairments. Analysis of the literature exploring the chronic effects of BFR + HIIT suggests that BFR does provide an additive physiological training stimulus to HIIT protocols, especially for measured aerobic, muscular, and, to some extent, anaerobic parameters. CONCLUSION: Presently, it appears that the addition of BFR into HIIT enhances physiological improvements in aerobic, muscular, and, to some extent, anaerobic performance. However due to large variability in permutations of BFR + HIIT methodologies, it is necessary for future research to explore and recommend standardised BFR guidelines for each HIIT exercise type.

Is Self-Determined Motivation a Useful Agent to Overcome Perceived Exercise Barriers in Patients With Type 2 Diabetes Mellitus?

Background: Devising a program to increase physical activity (PA)/exercise behavior in patients with type 2 diabetes mellitus (T2DM) can meet with limited effectiveness in real-world settings because of the variety of barriers to PA/exercise that individuals need to overcome. An alternative approach is to explore whether targeting motivation as a facilitator may be effective to increase PA/exercise. This study aimed to understand attitudes toward perceived barriers to PA/exercise by examining individual levels of motivation, grounded on self-determination theory, in patients with T2DM. Methods: This study used an integrated approach combining qualitative and quantitative analysis. Sixteen patients with T2DM were grouped (n = 8 for each group) into either a higher self-motivation (HSM) or lower self-motivation (LSM) group via the Relative Autonomy Index. Thematic and deductive analysis were used to identify attitudes based on ten preconceived barrier themes: apathy, dislike, no priority, lack of support, health problems, lack of knowledge, unfavorable environment, tiredness, lack of time, and financial constraints. Quantitative analysis was to assess statistical differences in the volume of PA/exercise across the two groups, and a mixed-methods analysis was employed to highlight unique cases. Results: Patients in the HSM group expressed positive attitudes toward barriers to PA/exercise, while patients in the LSM group expressed a greater degree of hindrance. Although regular PA/exercise is necessary for T2DM management, patients with LSM considered PA/exercise a lesser priority displaying negative attitudes such as apathy and dislike. Conversely, patients with HSM placed greater emphasis on the benefits of PA/exercise regardless of apathy and dislike. Lack of time and health problems were commonly reported in both groups. The volume of PA/exercise corresponded to motivation levels, but there were some unique cases which arose from active commuting habits and severe health problems. Conclusion: These findings provide insights on how attitudes to perceived barriers to PA/exercise differ by levels of motivation. One insight was that examining motivation should be an essential consideration when designing practical strategies to overcome PA/exercise barriers in patients with T2DM. Lack of time and health problems exist regardless of motivation levels. Future research requires a tailored approach to managing barriers to PA/exercise in patients with T2DM.

Reliability of a Novel Badminton Intermittent Exercise Protocol.

Purpose: Badminton is a sport characterized by high-intensity activity interspersed with short rests requiring specific physiological fitness, skills and game tactics. This study aimed to develop, describe and establish the reliability of a novel badminton intermittent exercise protocol, to simulate singles match-play (Part A) and assess match-fitness (Part B). Method: Twelve well-trained male badminton players performed a two-part protocol, mimicking the demands and activity of match-play, on two occasions with at least 72-h recovery. Part A imitated match-play and consisted of 40 stages alternating between 20 s work - receiving shuttlecocks from a launcher and ghosting (simulated) actions - and 40 s rest. Part B was an open-ended period, challenging match-fitness, designed to exhaust participants within 10 min. Physiological responses (heart rate, blood lactate and ratings of perceived exertion) (Part A and B) and time to exhaustion (Part B) were determined both times. Results: There were no differences in performance and physiological responses between trials (p > .05). The protocol demonstrated excellent reliability (intraclass correlation coefficient > 0.89) for all variables. Time to exhaustion (Part B) was 198 ± 98 s and 194 ± 82 s, respectively. Mean (Part A) and peak (Part B) heart rates were 166 ± 9; 191 ± 8 b∙min-1 and 166 ± 9; 191 ± 7 b∙min-1 and blood lactate concentrations (Part B) 11.8 ± 2.3 and 11.5 ± 2.1 mmol∙l-1 for trials 1 and 2, respectively. Conclusion: The protocol reliably induces match-like responses and can be used to assess match-fitness for training/research purposes.

Effects of Caffeine Supplementation on Performance in Ball Games.

Although a large body of evidence exists documenting the ergogenic properties of caffeine, most studies have focused on endurance performance. However, findings from endurance sports cannot be generalized to performance in ball games where, apart from having a high level of endurance, successful athletic performances require a combination of physiological, technical and cognitive capabilities. The purpose of this review was to critically evaluate studies that have examined the effect of a single dose of caffeine in isolation on one or more of the following performance measures: total distance, sprint performance, agility, vertical jump performance and accuracy in ball games. Searches of three major databases resulted in 19 studies (invasion games: 13; net-barrier games: 6) that evaluated the acute effects of caffeine on human participants, provided the caffeine dose administered, and included a ball games specific task or simulated match. Improvements in sprint performance were observed in 8 of 10 studies (80%), and vertical jump in 7 of 8 studies (88%). Equivocal results were reported for distance covered, agility and accuracy. Minor side effects were reported in 4 of 19 studies reviewed. Pre-exercise caffeine ingestion between 3.0 and 6.0 mg/kg of body mass appears to be a safe ergogenic aid for athletes in ball games. However, the efficacy of caffeine varies depending on various factors, including, but not limited to, the nature of the game, physical status and caffeine habituation. More research is warranted to clarify the effects of caffeine on performance measures unique to ball games, such as agility and accuracy. It is essential that athletes, coaches and practitioners evaluate the risk-benefit ratio of caffeine ingestion strategies on an individual case-by-case basis.

Oxygen consumption, substrate oxidation, and blood pressure following sprint interval exercise.

UNLABELLED: This study examined the acute effect of sprint interval exercise (SIE) on postexercise oxygen consumption, substrate oxidation, and blood pressure. The participants were 10 healthy males aged 21-27 years. Following overnight fasts, each participant undertook 2 trials in a random balanced order: (i) four 30-s bouts of SIE on a cycle ergometer, separated by 4.5 min of recovery, and (ii) resting (control) in the laboratory for an equivalent period. Time-matched measurements of oxygen consumption, respiratory exchange ratio, and blood pressure were made for 2 h into recovery. Total 2-h oxygen consumption was significantly higher in the SIE than in the control trial (mean ± SD: CONTROL: 31.9 ± 6.7 L vs Exercise: 45.5 ± 6.8 L, p < 0.001). The rate of fat oxidation was 75% higher 2 h after the exercise trial compared with the control trial ( CONTROL: 0.08 ± 0.05 g·min(-1) vs Exercise: 0.14 ± 0.06 g·min(-1), p = 0.035). Systolic blood pressure ( CONTROL: 117 ± 8 mm Hg vs Exercise: 109 ± 8 mm Hg, p < 0.05) and diastolic blood pressure ( CONTROL: 84 ± 6 mm Hg vs Exercise: 77 ± 5 mm Hg, p < 0.05) were significantly lower 2 h after the exercise trial compared with the control trial. These data showed a 42% increase in oxygen consumption (∼13.6 L) over 2 h after a single bout of SIE. Moreover, the rate of fat oxidation increased by 75%, whereas blood pressure was reduced by ∼8 mm Hg 2 h after SIE. Whether these acute benefits of SIE can translate into long-term changes in body composition and an improvement in vascular health needs investigation.