Stephen S. Cheung
Trine M. Seeberg, Jan Kocbach, Rune Kjøsen Talsnes, Frederic Meyer, Thomas Losnegard, Johannes Tjønnås, Øyvind Sandbakk, and Guro Strøm Solli
Purpose: To investigate the performance effects of video- and sensor-based feedback for implementing a terrain-specific micropacing strategy in cross-country (XC) skiing. Methods: Following a simulated 10-km skating time trial (Race1) on snow, 26 national-level male XC skiers were randomly allocated into an intervention (n = 14) or control group (n = 12), before repeating the race (Race2) 2 days later. Between races, intervention received video- and sensor-based feedback through a theoretical lecture and a practical training session aiming to implement a terrain-specific micropacing strategy focusing on active power production over designated hilltops to save time in the subsequent downhill. The control group only received their overall results and performed a training session with matched training load. Results: From Race1 to Race2, the intervention group increased the total variation of chest acceleration on all hilltops (P < .001) and reduced time compared with the control group in a specifically targeted downhill segment (mean group difference: −0.55 s; 95% confidence interval [CI], −0.9 to −0.19 s; P = .003), as well as in overall time spent in downhill (−14.4 s; 95% CI, −21.4 to −7.4 s; P < .001) and flat terrain (−6.5 s; 95% CI, −11.0 to −1.9 s; P = .006). No between-groups differences were found for either overall uphill terrain (−9.3 s; 95% CI, −31.2 to 13.2 s; P = .426) or total race time (−32.2 s; 95% CI, −100.2 to 35.9 s; P = .339). Conclusion: Targeted training combined with video- and sensor-based feedback led to a successful implementation of a terrain-specific micropacing strategy in XC skiing, which reduced the time spent in downhill and flat terrain for intervention compared with a control group. However, no change in overall performance was observed between the 2 groups of XC skiers.
Robert P. Lamberts, Teun van Erp, Dajo Sanders, Karen E. Welman, and Øyvind Sandbakk
José Afonso, Fábio Yuzo Nakamura, Ivan Baptista, Gonçalo Rendeiro-Pinho, João Brito, and Pedro Figueiredo
Purpose: Microdosing of exercise aims to deliver smaller daily training doses but at a higher weekly frequency, adding up to a similar weekly volume as in nonmicrodosed training. This commentary critically discusses this concept, which appears to be a rebranding of the “old” distributed practice of motor learning. Development: We propose that microdosing should relate to the minimal dose that develops or at least maintains the selected capacities or skills as this training dose matters to practitioners, especially during the in-season period. Moreover, microdosing has been applied mainly to develop strength and endurance, but abilities such as sprinting and changing direction could also be microdosed, as well as technical–tactical skills. Conclusions: The concept of microdosing should be reframed to avoid redundancy with the concept of distributed practice while providing valuable information concerning the minimum doses that still generate the intended effects and the thresholds that determine whether a dose is “micro” or not.
Tommy Slater, William J.A. Mode, Mollie G. Pinkney, John Hough, Ruth M. James, Craig Sale, Lewis J. James, and David J. Clayton
Acute morning fasted exercise may create a greater negative 24-hr energy balance than the same exercise performed after a meal, but research exploring fasted evening exercise is limited. This study assessed the effects of 7-hr fasting before evening exercise on energy intake, metabolism, and performance. Sixteen healthy males and females (n = 8 each) completed two randomized, counterbalanced trials. Participants consumed a standardized breakfast (08:30) and lunch (11:30). Two hours before exercise (16:30), participants consumed a meal (543 ± 86 kcal; FED) or remained fasted (FAST). Exercise involved 30-min cycling (∼60% VO2peak) and a 15-min performance test (∼85% VO2peak; 18:30). Ad libitum energy intake was assessed 15 min postexercise. Subjective appetite was measured throughout. Energy intake was 99 ± 162 kcal greater postexercise (p < .05), but 443 ± 128 kcal lower over the day (p < .001) in FAST. Appetite was elevated between the preexercise meal and ad libitum meal in FAST (p < .001), with no further differences (p ≥ .458). Fat oxidation was greater (+3.25 ± 1.99 g), and carbohydrate oxidation was lower (−9.16 ± 5.80 g) during exercise in FAST (p < .001). Exercise performance was 3.8% lower in FAST (153 ± 57 kJ vs. 159 ± 58 kJ, p < .05), with preexercise motivation, energy, readiness, and postexercise enjoyment also lower in FAST (p < .01). Fasted evening exercise reduced net energy intake and increased fat oxidation compared to exercise performed 2 hr after a meal. However, fasting also reduced voluntary performance, motivation, and exercise enjoyment. Future studies are needed to examine the long-term effects of this intervention as a weight management strategy.
Cindy H.P. Sit, Wendy Y.J. Huang, Stephen H.S. Wong, Martin C.S. Wong, Raymond K.W. Sum, and Venus M.H. Li
Background: Following the 2019 Hong Kong Para Report Card, the 2022 Hong Kong Para Report Card aimed to provide an updated and evidence-based assessment for nine indicators related to physical activity in children and adolescents with special educational needs and to assess the results using a SWOT (strengths, weaknesses, opportunities, and threats) analysis. Methods: Using a systematic process, the best available data on nine indicators were searched from the past 10 years and were assessed by a research work group. Letter grades were assigned and considered by stakeholders and auditors. Results: Four indicators were assigned a letter grade (overall physical activity: F [mixed device-measured and self-reported data]; sedentary behaviors: D [device-measured data]; active transportation: D−; government strategies & investment: C+). SWOT analysis highlighted opportunities for facilitating children and adolescents with special educational needs to achieve health recommendations. Conclusion: There were deteriorating trends in physical activity and sedentary behaviors. Effective, multilevel, and cross-sector interventions are recommended to promote active behavior in children and adolescents with special educational needs.
Susann Arnell, Kajsa Jerlinder, and Lars-Olov Lundqvist
Background: Participation in physical activity among adolescents with autism is often conditional. However, there is a lack of methods for identifying these specific conditions. Therefore, the purpose of this study was to develop and investigate the feasibility of a Q-sort tool to map individual-specific conditions for participation in physical activity among adolescents with autism and to identify different viewpoints regarding conditions for such participation. Method: An exploratory mixed-methods design was employed to investigate the feasibility of using Q methodology and the Q-sort procedure to identify what individual-specific conditions are important for participation in physical activity for adolescents with autism. Results: The adolescents ranked the statements with varying levels of ease. Two viewpoints were identified: Autonomous participation without surprises and Enjoyment of activity in a safe social context. Conclusion: Q-sort is a feasible method for mapping conditions for participation, which can guide the development of tailored physical activity interventions.
Charles S. Urwin, Rodney J. Snow, Dominique Condo, Rhiannon M.J. Snipe, Glenn D. Wadley, Lilia Convit, and Amelia J. Carr
This study compared the recommended dose of sodium citrate (SC, 500 mg/kg body mass) and sodium bicarbonate (SB, 300 mg/kg body mass) for blood alkalosis (blood [HCO3 −]) and gastrointestinal symptoms (GIS; number and severity). Sixteen healthy individuals ingested the supplements in a randomized, crossover design. Gelatin capsules were ingested over 15 min alongside a carbohydrate-rich meal, after which participants remained seated for forearm venous blood sample collection and completion of GIS questionnaires every 30 min for 300 min. Time-course and session value (i.e., peak and time to peak) comparisons of SC and SB supplementation were performed using linear mixed models. Peak blood [HCO3 −] was similar for SC (mean 34.2, 95% confidence intervals [33.4, 35.0] mmol/L) and SB (mean 33.6, 95% confidence intervals [32.8, 34.5] mmol/L, p = .308), as was delta blood [HCO3 −] (SC = 7.9 mmol/L; SB = 7.3 mmol/L, p = .478). Blood [HCO3 −] was ≥6 mmol/L above baseline from 180 to 240 min postingestion for SC, significantly later than for SB (120–180 min; p < .001). GIS were mostly minor, and peaked 80–90 min postingestion for SC, and 35–50 min postingestion for SB. There were no significant differences for the number or severity of GIS reported (p > .05 for all parameters). In summary, the recommended doses of SC and SB induce similar blood alkalosis and GIS, but with a different time course.
Christopher Byrne, Aurelien Cosnefroy, Roger Eston, Jason K.W. Lee, and Tim Noakes
Purpose: To continuously measure body core temperature (T c) throughout a mass-participation ultramarathon in subelite recreational runners to quantify T c magnitude and the influence of aerobic fitness and body fat. Methods: Twenty-three participants (19 men and 4 women; age 45  y; body mass 72.0 [9.3] kg; body fat 26% [6%]; peak oxygen uptake 50  mL·kg−1·min−1) had gastrointestinal temperature measured during an 89-km ultramarathon. Prerace-to-postrace changes in body mass, plasma sodium, and fluid and food recall quantified body water balance. Results: In maximal environmental conditions of 26.3 °C and 53% humidity, 21 of the 23 participants finished in 10:28 (01:10) h:min while replacing 49% (27%) of sweat losses, maintaining plasma sodium (140  mmol·L−1), and dehydrating by 4.1% (1.3%). Mean maximum T c was 39.0 (0.5) (range 38.2–40.1 °C) with 90% of race duration ≤39.0 °C. Mean maximum ΔT c was 1.9 (0.9) (0.9–2.7 °C) with 95% of race duration ≤2.0 °C. Over 0 to 45 km, associations between ΔT c and peak oxygen uptake (positive) and body fat (negative) were observed. Over 58 to 89 km, associations between T c and peak oxygen uptake (negative) and body fat (positive) were observed. Conclusions: Modest T c responses were observed in recreational ultramarathon runners. Runners with higher levels of aerobic fitness and lower levels of body fat demonstrated the greatest changes in T c during the first half of the race. Conversely, runners with lower levels of aerobic fitness and higher levels of body fat demonstrated the greatest absolute T c in the final third of the race.
Tim Podlogar, Simon Cirnski, Špela Bokal, Nina Verdel, and Javier T. Gonzalez
It was previously demonstrated that postexercise ingestion of fructose–glucose mixtures can lead to superior liver and equal muscle glycogen synthesis as compared with glucose-based carbohydrates (CHOs) only. After an overnight fast, liver glycogen stores are reduced, and based on this we hypothesized that addition of fructose to a glucose-based breakfast would lead to improved subsequent endurance exercise capacity. In this double-blind cross-over randomized study (eight males, peak oxygen uptake: 62.2 ± 5.4 ml·kg−1·min−1), participants completed two experimental trials consisting of two exercise bouts. In the afternoon of Day 1, they completed a cycling interval training session to normalize glycogen stores after which a standardized high-CHO diet was provided for 4 hr. On Day 2, in the morning, participants received 2 g/kg of CHOs in the form of glucose and rice or fructose and rice, both in a CHO ratio of 1:2. Two hours later they commenced cycling exercise session at the intensity of the first ventilatory threshold until task failure. Exercise capacity was higher in fructose and rice (137.0 ± 22.7 min) as compared with glucose and rice (130.06 ± 19.87 min; p = .046). Blood glucose and blood lactate did not differ between the trials (p > .05) and neither did CHO and fat oxidation rates (p > .05). However, due to the duration of exercise, total CHO oxidation was higher in fructose and rice (326 ± 60 g vs. 298 ± 61 g, p = .009). Present data demonstrate that addition of fructose to a glucose-based CHO source at breakfast improves endurance exercise capacity. Further studies are required to determine the mechanisms and optimal dose and ratio.