Alannah K.A. McKay, Peter Peeling, David B. Pyne, Nicolin Tee, Marijke Welveart, Ida A. Heikura, Avish P. Sharma, Jamie Whitfield, Megan L. Ross, Rachel P.L. van Swelm, Coby M. Laarakkers and Louise M. Burke
This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17–23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p = .004) and hotter trial ambient temperatures (p = .014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise.
Megan A. Kuikman, Margo Mountjoy, Trent Stellingwerff and Jamie F. Burr
Relative energy deficiency in sport (RED-S) can result in negative health and performance outcomes in both male and female athletes. The underlying etiology of RED-S is low energy availability (LEA), which occurs when there is insufficient dietary energy intake to meet exercise energy expenditure, corrected for fat-free mass, leaving inadequate energy available to ensure homeostasis and adequate energy turnover (optimize normal bodily functions to positively impact health), but also optimizing recovery, training adaptations, and performance. As such, treatment of RED-S involves increasing energy intake and/or decreasing exercise energy expenditure to address the underlying LEA. Clinically, however, the time burden and methodological errors associated with the quantification of energy intake, exercise energy expenditure, and fat-free mass to assess energy availability in free-living conditions make it difficult for the practitioner to implement in everyday practice. Furthermore, interpretation is complicated by the lack of validated energy availability thresholds, which can result in compromised health and performance outcomes in male and female athletes across various stages of maturation, ethnic races, and different types of sports. This narrative review focuses on pragmatic nonpharmacological strategies in the treatment of RED-S, featuring factors such as low carbohydrate availability, within-day prolonged periods of LEA, insufficient intake of bone-building nutrients, lack of mechanical bone stress, and/or psychogenic stress. This includes the implementation of strategies that address exacerbating factors of LEA, as well as novel treatment methods and underlying mechanisms of action, while highlighting areas of further research.
Haiko B. Zimmermann, Débora Knihs, Fernando Diefenthaler, Brian MacIntosh and Juliano Dal Pupo
Purpose: The objective of this study was to analyze the effects of a conditioning activity (CA) composed of continuous countermovement jumps on twitch torque production and 30-m sprint times. Methods: A total of 12 sprint athletes, 10 men (23.5 [7.7] y) and 2 women (23.0 [2.8] y), volunteered to participate in this study. The participants were evaluated in 2 sessions as follows: (1) to determine the effects of the CA (3 sets of 5 continuous vertical jumps with a 1-min interval between sets) on 30-m sprint performance over time (2, 4, 6, 8, and 10 min) and (2) to evaluate twitch peak torque to determine the magnitude and time course of the induced postactivation potentiation at the same recovery intervals. Results: Mixed-model analysis of variance with Bonferroni post hoc verified that there was a decrease on the 30-m sprint time at 2 minutes (P = .01; Δ = 2.78%; effect size [ES] = 0.43) and 4 minutes (P = .02; Δ = 2%, ES = 0.30) compared with pre when the CA preceded the sprints. The peak torque of quadriceps also showed significant increase from pretest to 2 minutes (P < .01; Δ = 17.0% [12.2%]; ES = 0.45) and 4 minutes (P = .02; Δ = 7.2% [8.8%]; ES = 0.20). Conclusion: The inclusion of CA composed of continuous countermovement jumps in the warm-up routine improved 30-m sprint performance at 2- and 4-minute time intervals after the CA (postactivation performance enhancement). Since postactivation potentiation was confirmed with electrical stimulation at the time when sprint performance increased, it was concluded that postactivation potentiation may have contributed to the observed performance increases.
Samantha M. Ross, Ellen Smit, Joonkoo Yun, Kathleen R. Bogart, Bridget E. Hatfield and Samuel W. Logan
A secondary data analysis of 33,093 children and adolescents age 6–17 years (12% with disabilities) from a 2016–2017 National Survey of Children’s Health nonrepresentative sample aimed to identify (a) unique clusters of sociodemographic characteristics and (b) the relative importance of disability status in predicting participation in daily physical activity (PA) and sports. Exploratory classification tree analyses identified hierarchical predictors of daily PA and sport participation separately. Disability status was not a primary predictor of daily PA. Instead, it emerged in the fifth level after age, sex, body mass index, and income, highlighting the dynamic intersection of disability with sociodemographic factors influencing PA levels. In comparison, disability status was a second-level predictor for sport participation, suggesting that unique factors influencing PA level are likely experienced by disabled children and adolescents. The authors employ an intersectionality lens to critically discuss implications for research in adapted PA.
Charles S. Urwin, Rodney J. Snow, Dominique Condo, Rhiannon Snipe, Glenn D. Wadley and Amelia J. Carr
This review aimed to identify factors associated with (a) physiological responses, (b) gastrointestinal (GI) symptoms, and (c) exercise performance following sodium citrate supplementation. A literature search identified 33 articles. Observations of physiological responses and GI symptoms were categorized by dose (< 500, 500, and > 500 mg/kg body mass [BM]) and by timing of postingestion measurements (in minutes). Exercise performance following sodium citrate supplementation was compared with placebo using statistical significance, percentage change, and effect size. Performance observations were categorized by exercise duration (very short < 60 s, short ≥ 60 and ≤ 420 s, and longer > 420 s) and intensity (very high > 100% VO2max and high 90–100% VO2max). Ingestion of 500 mg/kg BM sodium citrate induced blood alkalosis more frequently than < 500 mg/kg BM, and with similar frequency to >500 mg/kg BM. The GI symptoms were minimized when a 500 mg/kg BM dose was ingested in capsules rather than in solution. Significant improvements in performance following sodium citrate supplementation were reported in all observations of short-duration and very high–intensity exercise with a 500 mg/kg BM dose. However, the efficacy of supplementation for short-duration, high-intensity exercise is less clear, given that only 25% of observations reported significant improvements in performance following sodium citrate supplementation. Based on the current literature, the authors recommend ingestion of 500 mg/kg BM sodium citrate in capsules to induce alkalosis and minimize GI symptoms. Supplementation was of most benefit to performance of short-duration exercise of very high intensity; further investigation is required to determine the importance of ingestion duration and timing.
Tomasz Skowronek, Grzegorz Juras and Kajetan J. Słomka
Purpose: To estimate the influence of global anaerobic fatigue on rhythm performance. Methods: Fifteen young males participated in the experiment. Anaerobic fatigue was induced with 2 consecutive running-based anaerobic sprint tests (RAST). The level of lactate was controlled before the first RAST and 3 minutes after each RAST. The rhythm performance was assessed by using Optojump Next (Microgate, Bolzano, Italy). The rhythm test was conducted 3 times, before fatigue and immediately after each RAST. Eight variables of the rhythm test were analyzed: the mean frequency of jumps for the assisted and unassisted phase (XfAP and XfUAP), SD of jump frequency for the assisted and unassisted phase (SDfAP and SDfUAP), and mean absolute error for the assisted and unassisted phases of the test (XERAP and XERUAP, respectively). Results: One-way repeated-measures analysis of variance showed a significant main effect of anaerobic effort on rhythm variables only in the unassisted phase of the test. Statistically significant differences were observed in XfUAP between the first and third rhythm measurements (F
2,28 = 4.98, P < .014,
Thomas Sawczuk, Ben Jones, Mitchell Welch, Clive Beggs, Sean Scantlebury and Kevin Till
Purpose: To evaluate the relative importance and predictive ability of salivary immunoglobulin A (s-IgA) measures with regards to upper respiratory illness (URI) in youth athletes. Methods: Over a 38-week period, 22 youth athletes (age = 16.8 [0.5] y) provided daily symptoms of URI and 15 fortnightly passive drool saliva samples, from which s-IgA concentration and secretion rate were measured. Kernel-smoothed bootstrapping generated a balanced data set with simulated data points. The random forest algorithm was used to evaluate the relative importance (RI) and predictive ability of s-IgA concentration and secretion rate with regards to URI symptoms present on the day of saliva sampling (URIday), within 2 weeks of sampling (URI2wk), and within 4 weeks of sampling (URI4wk). Results: The percentage deviation from average healthy s-IgA concentration was the most important feature for URIday (median RI 1.74, interquartile range 1.41–2.07). The average healthy s-IgA secretion rate was the most important feature for URI4wk (median RI 0.94, interquartile range 0.79–1.13). No feature was clearly more important than any other when URI symptoms were identified within 2 weeks of sampling. The values for median area under the curve were 0.68, 0.63, and 0.65 for URIday, URI2wk, and URI4wk, respectively. Conclusions: The RI values suggest that the percentage deviation from average healthy s-IgA concentration may be used to evaluate the short-term risk of URI, while the average healthy s-IgA secretion rate may be used to evaluate the long-term risk. However, the results show that neither s-IgA concentration nor secretion rate can be used to accurately predict URI onset within a 4-week window in youth athletes.