Purpose: To determine if the mathematical model used to derive critical power could be used to identify the critical resistance (CR) for the deadlift; compare predicted and actual repetitions to failure at 50%, 60%, 70%, and 80% 1-repetition maximum (1RM); and compare the CR with the estimated sustainable resistance for 30 repetitions (ESR30). Methods: Twelve subjects completed 1RM testing for the deadlift followed by 4 visits to determine the number of repetitions to failure at 50%, 60%, 70%, and 80% 1RM. The CR was calculated as the slope of the line of the total work completed (repetitions × weight [in kilograms] × distance [in meters]) vs the total distance (in meters) the barbell traveled. The actual and predicted repetitions to failure were determined from the CR model and compared using paired-samples t tests and simple linear regression. The ESR30 was determined from the power-curve analysis and compared with the CR using paired-samples t tests and simple linear regression. Results: The weight and repetitions completed at CR were 56 (11) kg and 49 (14) repetitions. The actual repetitions to failure were less than predicted at 50% 1RM (P < .001) and 80% 1RM (P < .001) and greater at 60% 1RM (P = .004), but there was no difference at 70% 1RM (P = .084). The ESR30 (75  kg) was greater (P < .001) than the CR. Conclusions: The total work-vs-distance relationship can be used to identify the CR for the deadlift, which reflected a sustainable resistance that may be useful in the design of resistance-based exercise programs.
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Taylor K. Dinyer, M. Travis Byrd, Ashley N. Vesotsky, Pasquale J. Succi and Haley C. Bergstrom
Rheanna Bulten, Sara King-Dowling and John Cairney
Purpose: To determine the validity of standing long jump (SLJ) for predicting muscle power in children with and without developmental coordination disorder (DCD). Methods: A total of 589 children were recruited as part of the Coordination and Activity Tracking in CHildren study (251 girls and 338 boys; mean age 59.2 mo). Children were classified as typically developing (>16th percentile), at risk for DCD (sixth to 16th percentile), or probable DCD (<sixth percentile) based on Movement Assessment Battery for Children—Second Edition scores. SLJ was measured from the back of the heel. Peak power and mean power over 10 seconds and 30 seconds were measured using the Wingate test. Results: SLJ was moderately correlated with peak and mean powers in all groups (R = .51–.55). Regression analysis showed that when combined with weight and age, SLJ performance could predict peak power and mean power over 10 seconds and 30 seconds in typically developing children (adjusted R 2 = .68, .61, and .58, P < .001, respectively) and in children with risk for DCD (adjusted R 2 = .74, .65, and .60, respectively) and probable DCD (adjusted R 2 = .68, .61, and .59, respectively). Conclusions: SLJ, in combination with weight and age, may be used to measure muscle power in typically developing children, and in children with risk for DCD and probable DCD. This measure can be used as an inexpensive estimate of musculoskeletal fitness in children regardless of motor abilities.
Andrzej Gawrecki, Aleksandra Araszkiewicz, Agnieszka Szadkowska, Grzegorz Biegański, Jan Konarski, Katarzyna Domaszewska, Arkadiusz Michalak, Bogda Skowrońska, Anna Adamska, Dariusz Naskręt, Przemysława Jarosz-Chobot, Agnieszka Szypowska, Tomasz Klupa and Dorota Zozulińska-Ziółkiewicz
Purpose: To assess glycemic control and safety of children and adolescents with type 1 diabetes participating in a 2-day football tournament. Methods: In total, 189 children with type 1 diabetes from 11 diabetes care centers, in Poland, participated in a football tournament in 3 age categories: 7–9 (21.2%), 10–13 (42.9%), and 14–17 (36%) years. Participants were qualified and organized in 23 football teams, played 4 to 6 matches of 30 minutes, and were supervised by a medical team. Data on insulin dose and glycemia were downloaded from personal pumps, glucose meters, continuous glucose monitoring, and flash glucose monitoring systems. Results: The median level of blood glucose before the matches was 6.78 (4.89–9.39) mmol/L, and after the matches, it was 7.39 (5.5–9.87) mmol/L (P = .001). There were no episodes of severe hypoglycemia or ketoacidosis. The number of episodes of low glucose value (blood glucose ≤3.9 mmol/L) was higher during the tournament versus 30 days before: 1.2 (0–1.5) versus 0.7 (0.3–1.1) event/person/day, P < .001. Lactate levels increased during the matches (2.2 [1.6–4.0] mmol/L to 4.4 [2.6–8.5] mmol/L after the matches, P < .001). Conclusions: Large football tournaments can be organized safely for children with type 1 diabetes. For the majority of children, moderate mixed aerobic–anaerobic effort did not adversely affect glycemic results and metabolic safety.
Leanna M. Ross, Jacob L. Barber, Alexander C. McLain, R. Glenn Weaver, Xuemei Sui, Steven N. Blair and Mark A. Sarzynski
Background: This study examined the cross-sectional and longitudinal associations of cardiorespiratory fitness (CRF) and ideal cardiovascular health (CVH). Methods: CRF and the 7 CVH components were measured in 11,590 (8865 males; 2725 females) adults at baseline and in 2532 (2160 males; 372 females) adults with at least one follow-up examination from the Aerobics Center Longitudinal Study. Ideal CVH score was calculated as a composite of 7 measures, each scored 0 to 2. CVH groups were based on participant point score: ≤7 (poor), 8 to 11 (intermediate), and 12 to 14 (ideal). Analyses included general linear, logistic regression, and linear mixed models. Results: At baseline, participants in the high CRF category had 21% and 45% higher mean CVH scores than those in the moderate and poor CRF categories (P < .001). The adjusted odds (95% confidence interval) of being in the poor CVH group at baseline were 4.9 (4.4–5.4) and 16.9 (14.3–19.9) times greater for individuals with moderate and low CRF, respectively, compared with those with high CRF (P < .001). Longitudinal analysis found that for every 1-minute increase in treadmill time, CVH score increased by 0.23 units (P < .001) independent of age, sex, exam number, and exam year. Conclusions: Higher CRF is associated with better CVH profiles, and improving CRF over time is independently associated with greater improvements in CVH.
Zhiguang Zhang, Eduarda Sousa-Sá, João R. Pereira, Anthony D. Okely, Xiaoqi Feng and Rute Santos
Background: This study examined the associations between environmental characteristics of early childhood education and care (ECEC) centers and 1-year change in toddlers’ physical activity and sedentary behavior while at the centers. Methods: Data from 292 toddlers from the GET-UP! study were analyzed. Environmental characteristics of ECEC centers were rated using the Infant/Toddler Environment Rating Scale-revised edition at baseline. Children’s physical activity and sedentary behavior in the centers were assessed using activPAL devices, at baseline and at 1-year follow-up. Linear mixed models were performed to examine the associations between the environmental characteristics and change in the proportion of time spent in physical activity and sedentary behavior. Results: Compared with baseline, children spent a higher proportion of time in sedentary behavior (sitting) but a lower proportion of time in standing and physical activity (stepping) while at ECEC centers, at 1-year follow-up. The environmental characteristics “interaction” (B = −1.39; P = .01) and “program structure” (B = −1.15; P = .04) were negatively associated with change in the proportion of time spent in physical activity. Conclusion: Better “interaction” and “program structure” may preclude children’s physical activity from declining over time and may be considered important features to target in future interventions in ECEC centers aiming at promoting active lifestyles.
Mauricio Castro-Sepulveda, Jorge Cancino, Rodrigo Fernández-Verdejo, Cristian Pérez-Luco, Sebastian Jannas-Vela, Rodrigo Ramirez-Campillo, Juan Del Coso and Hermann Zbinden-Foncea
During exercise, the human body maintains optimal body temperature through thermoregulatory sweating, which implies the loss of water, sodium (Na+), and other electrolytes. Sweat rate and sweat Na+ concentration show high interindividual variability, even in individuals exercising under similar conditions. Testosterone and cortisol may regulate sweat Na+ loss by modifying the expression/activity of the cystic fibrosis transmembrane conductance regulator. This has not been tested. As a first approximation, the authors aimed to determine whether basal serum concentrations of testosterone or cortisol, or the testosterone/cortisol ratio relate to sweat Na+ loss during exercise. A total of 22 male elite soccer players participated in the study. Testosterone and cortisol were measured in blood samples before exercise (basal). Sweat samples were collected during a training session, and sweat Na+ concentration was determined. The basal serum concentrations of testosterone and cortisol and their ratio were (mean [SD]) 13.6 (3.3) pg/ml, 228.9 (41.4) ng/ml, and 0.06 (0.02), respectively. During exercise, the rate of Na+ loss was related to cortisol (r = .43; p < .05) and to the testosterone/cortisol ratio (r = −.46; p < .01), independently of the sweating rate. The results suggest that cortisol and the testosterone/cortisol ratio may influence Na+ loss during exercise. It is unknown whether this regulation depends on the cystic fibrosis transmembrane conductance regulator.
Marc-Olivier St-Aubin, Philippe Chalaye, François-Pierre Counil and Sylvie Lafrenaye
Purpose: To evaluate exercise-induced analgesia (EIA) effectiveness in healthy adolescent males and to investigate possible associations between EIA and physiological/psychological variables. Methods: Twenty-eight healthy adolescent males (14–17 y) participated in this study. EIA was evaluated by comparing perceptions of heat pain stimulations before and after an increasing maximal load test on a cycle ergometer (VO2max). Results: Pain intensity for mild and strong heat pain stimulations significantly decreased following physical exercise (mild: EIA = 28.6%; 95% confidence interval, 0.9–1.9; P < .001 and strong: EIA = 11.3%; 95% confidence interval, 0.3–1.4; P = .002). The number of physical activity hours per week was positively correlated with the effectiveness of EIA for mild and strong pain intensity (r = .41, P = .03 and r = .43, P = .02, respectively). Conclusions: Intense physical exercise decreases perception of intensity of experimental heat pain in healthy adolescent males. The least physically active adolescents have reduced EIA effectiveness to experimental heat pain stimulations compared with physically active ones. Adolescents adopting an active lifestyle have more endogenous pain inhibition and could, therefore, potentially be less disposed to suffer from chronic pain later in life.
Lauren Anne Lipker, Caitlyn Rae Persinger, Bradley Steven Michalko and Christopher J. Durall
Clinical Scenario: Quadriceps atrophy and weakness are common after anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) therapy, alone or in combination with exercise, has shown some promise in promoting muscular hypertrophy. This review was conducted to ascertain the extent to which current evidence supports the use of BFR for reducing quadriceps atrophy following ACLR in comparison with standard care. Clinical Question: Is BFR more effective than standard care for reducing quadriceps atrophy after ACLR? Summary of Key Findings: The literature was searched for studies that directly compared BFR treatment to standard care in patients with ACLR. Three level I randomized control trial studies retrieved from the literature search met the inclusion criteria. Clinical Bottom Line: Reviewed data suggest that a short duration (13 d) of moderate-pressure BFR combined with low-resistance muscular training does not appear to measurably affect quadriceps cross-sectional area. However, a relatively long duration (15 wk) of moderate-pressure BFR combined with low-resistance muscular training may increase quadriceps cross-sectional area to a greater extent than low-resistance muscular training alone. The results of the third randomized control trial suggest that employing BFR while immobilized in the early postoperative period may reduce quadriceps atrophy following ACLR. Additional data are needed to establish if the benefits of BFR on quadriceps atrophy after ACLR outweigh the inherent risks and costs. Strength of Recommendation: All evidence for this review was level 1 (randomized control trial) based on the Centre for Evidence-Based Medicine criteria. However, the findings were inconsistent across the 3 studies regarding the effects of BFR on quadriceps atrophy resulting in a grade “B” strength of recommendation.
Zhen Zeng, Christoph Centner, Albert Gollhofer and Daniel König
Purpose: Setting the optimal cuff pressure is a crucial part of prescribing blood-flow-restriction training. It is currently recommended to use percentages of each individual’s arterial occlusion pressure, which is most accurately determined by Doppler ultrasound (DU). However, the practicality of this gold-standard method in daily training routine is limited due to high costs. An alternative solution is pulse oximetry (PO). The main purpose of this study was to evaluate validity between PO and DU measurements and to investigate whether sex has a potential influence on these variables. Methods: A total of 94 subjects were enrolled in the study. Participants were positioned in a supine position, and a 12-cm-wide cuff was applied in a counterbalanced order at the most proximal portion of the right upper and lower limbs. The cuff pressure was successively increased until pulse was no longer detected by DU and PO. Results: There were no significant differences between the DU and PO methods when measuring arterial occlusion pressure at the upper limb (P = .308). However, both methods showed considerable disagreement for the lower limbs (P = .001), which was evident in both men (P = .028) and women (P = .008). No sex differences were detected. Conclusions: PO is reasonably accurate to determine arterial occlusion pressure of the upper limbs. For lower limbs, PO does not seem to be a valid instrument when assessing the optimal cuff pressure for blood-flow-restriction interventions compared with DU.
Emily C. Borden, William J. Kraemer, Bryant J. Walrod, Emily M. Post, Lydia K. Caldwell, Matthew K. Beeler, William H. DuPont, John Paul Anders, Emily R. Martini, Jeff S. Volek and Carl M. Maresh
Purpose: To evaluate the changes in the state of hydration in elite National Collegiate Athletic Association (NCAA) Division I college wrestlers during and after a season. Methods: Ohio State University wrestling team members (N = 6; mean [SD] age = 19.6 [1.1] y; height = 171.6 [2.9] cm; body mass = 69.5 [8.1] kg) gave informed consent to participate in the investigation with measurements (ie, body mass, urine-specific gravity [USG; 2 methods], Visual Analog Scale thirst scale, plasma osmolality) obtained during and after the season. Results: Measurements for USG, regardless of methods, were not significantly different between visits, but plasma osmolality was significantly (P = .001) higher at the beginning of the season—295.5 (4.9) mOsm·kg−1 compared with 279.6 (6.1) mOsm·kg−1 after the season. No changes in thirst ratings were observed, and the 2 measures of USG were highly correlated (r > .9, P = .000) at each time point, but USG and plasma osmolality were not related. Conclusions: A paradox in the clinical interpretation of euhydration in the beginning of the season was observed with the USG, indicating that the wrestlers were properly hydrated, while the plasma osmolality showed they were not. Thus, the tracking of hydration status during the season is a concern when using only NCAA policies and procedures. The wrestlers did return to normal euhydration levels after the season on both biomarkers, which is remarkable, as previous studies have indicated that this may not happen because of the reregulation of the osmol-regulatory center in the brain.