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Kay Winkert, Johannes Kirsten, Rupert Kamnig, Jürgen M. Steinacker, and Gunnar Treff

Purpose: Automated metabolic analyzers are frequently utilized to measure maximal oxygen consumption (V˙O2max). However, in portable devices, the results may be influenced by the analyzer’s technological approach, being either breath-by-breath (BBB) or dynamic micro mixing chamber mode (DMC). The portable metabolic analyzer K5 (COSMED, Rome, Italy) provides both technologies within one device, and the authors aimed to evaluate differences in V˙O2max between modes in endurance athletes. Methods: Sixteen trained male participants performed an incremental test to voluntary exhaustion on a cycle ergometer, while ventilation and gas exchange were measured by 2 structurally identical COSMED K5 metabolic analyzers synchronously, one operating in BBB and the other in DMC mode. Except for the flow signal, which was measured by 1 sensor and transmitted to both devices, the devices operated independently. V˙O2max was defined as the highest 30-second average. Results: V˙O2max and V˙CO2@V˙O2max were significantly lower in BBB compared with DMC mode (−4.44% and −2.71%), with effect sizes being large to moderate (ES, Cohen d = 0.82 and 1.87). Small differences were obtained for respiratory frequency (0.94%, ES = 0.36), minute ventilation (0.29%, ES = 0.20), and respiratory exchange ratio (1.74%, ES = 0.57). Conclusion: V˙O2max was substantially lower in BBB than in DMC mode. Considering previous studies that also indicated lower V˙O2 values in BBB at high intensities and a superior validity of the K5 in DMC mode, the authors conclude that the DMC mode should be selected to measure V˙O2max in athletes.

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Tomonari Takeshita, Hiroaki Noro, Keiichiro Hata, Taira Yoshida, Tetsuo Fukunaga, and Toshio Yanagiya

The present study aimed to clarify the effect of the foot strike pattern on muscle–tendon behavior and kinetics of the gastrocnemius medialis during treadmill running. Seven male participants ran with 2 different foot strike patterns (forefoot strike [FFS] and rearfoot strike [RFS]), with a step frequency of 2.50 Hz and at a speed of 2.38 m/s for 45 seconds on a treadmill with an instrumented force platform. The fascicle behavior of gastrocnemius medialis was captured using a B-mode ultrasound system with a sampling rate of 75 Hz, and the mechanical work done and power exerted by the fascicle and tendon were calculated. At the initial contact, the fascicle length was significantly shorter in the FFS than in the RFS (P = .001). However, the fascicular velocity did not differ between strike patterns. Higher tendon stretch and recoil were observed in the FFS (P < .001 and P = .017, respectively) compared with the RFS. The fascicle in the positive phase performed the same mechanical work in both the FFS and RFS; however, the fascicle in the negative phase performed significantly greater work in the FFS than in the RFS (P = .001). RFS may be advantageous for requiring less muscular work and elastic energy in the series elastic element compared with the FFS.

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Cristiano Dall’ Agnol, Tiago Turnes, and Ricardo Dantas De Lucas

Purpose: Cyclists may increase exercise intensity by prolonging exercise duration and/or shortening the recovery period during self-paced interval training, which could impact the time spent near V˙O2max. Thus, the main objective of this study was to compare the time spent near V˙O2max during 4 different self-paced interval training sessions. Methods: After an incremental test, 11 cyclists (mean [SD]: age = 34.4 [6.2] y; V˙O2max=55.7[7.4]mL·kg1·min1) performed in a randomized order 4 self-paced interval training sessions characterized by a work–recovery ratio of 4:1 or 2:1. Sessions comprised 4 repetitions of 4 minutes of cycling with 1 minute (4/1) or 2 minutes (4/2) of active recovery or 8 minutes of cycling with 2 minutes (8/2) or 4 minutes (8/4) of active recovery. Time spent at 90% to 94% (t90V˙O2max), ≥95% (t95V˙O2max), and 90% to 100% V˙O2max (tV˙O2max) was analyzed in absolute terms and relative to the total work duration. Power output, heart rate, blood lactate, and rating of perceived exertion were compared. Results: The 8/4 session provided higher absolute tV˙O2max and t95V˙O2max than 8/2 (P = .015 and .029) and 4/1 (P = .002 and .047). The 4/2 protocol elicited higher relative tV˙O2max (47.7% [26.9%]) and t95V˙O2max (23.5% [22.7%]) than 4/1 (P = .015 and .028) and 8/2 (P < .01). Session 4/2 (275 [23] W) elicited greater mean power output (P < .01) than 4/1 (261 [27] W), 8/4 (250 [25] W), and 8/2 (234 [23] W). Conclusions: Self-paced interval training composed of 4-minute and 8-minute work periods efficiently elicit tV˙O2max, but protocols with a work–recovery ratio of 2:1 (ie, 4/2 and 8/4) could be prioritized to maximize tV˙O2max.

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Danica Janicijevic, Ivan Jukic, Jonathon Weakley, and Amador García-Ramos

Purpose: To compare the accuracy of nine 1-repetition maximum (1RM) prediction methods during the paused and touch-and-go bench press exercises performed in a Smith machine. Method: A total of 86 men performed 2 identical sessions (incremental loading test until reaching the 1RM followed by a set to failure) in a randomized order during the paused and touch-and-go bench press exercises. Individualized load–velocity relationships were modeled by linear and polynomial regression models considering 4 loads (45%–60%–75%–90% of 1RM) (multiple-point methods) and considering only 2 loads (45%–90% of 1RM) by a linear regression (2-point method). Three minimal velocity thresholds were used: the general velocity of 0.17 m·s−1 (general velocity of the 1RM [V1RM]), the velocity obtained when lifting the 1RM load (individual V1RM), and the velocity obtained during the last repetition of a set to failure. Results: The 1RM prediction methods were generally valid (range: r = .96–.99, standard error of the estimate = 2.8–4.9 kg or 4.6%–8.0% of 1RM). The multiple-point linear method (2.79 [2.29] kg) was more precise than the multiple-point polynomial method (3.54 [3.31] kg; P = .013), but no significant differences were observed when compared with the 2-point method (3.09 [2.66] kg, P = .136). The velocity of the last repetition of a set to failure (3.47 [2.97] kg) was significantly less precise than the individual V1RM (2.91 [2.75] kg, P = .009) and general V1RM (3.00 [2.65] kg, P = .010). Conclusions: Linear regression models and a general minimal velocity threshold of 0.17 m·s−1 should be recommended to obtain a quick and precise estimation of the 1RM during the bench press exercise performed in a Smith machine.

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C. Eric Heidorn, Brandon J. Dykstra, Cori A. Conner, and Anthony D. Mahon

Purpose: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. Methods: A total of 10 girls (10.4 [0.7] y) participated in the study. VO2peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO2peak and maximal sprints) before a 1-minute performance sprint. Results: The mean power, peak power, heart rate (HR), %HRpeak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HRpeak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). Conclusion: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

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Nils Swindell, Damon Berridge, Melitta A. McNarry, Kelly A. Mackintosh, Lynne M. Boddy, Stuart J. Fairclough, and Gareth Stratton

Purpose:To examine (1) associations between body fat percent (BF) and lifestyle behaviors in children aged 9–11 years and (2) the consistency of these associations over a 10-year period. Methods: In this repeat, cross-sectional study, 15,977 children aged 9–11 years completed an anthropometric assessment and the SportsLinx Lifestyle survey between 2004 and 2013. Body fat was estimated according to the sum of the triceps and subscapular skinfold measurements. Multilevel models were utilized to examine associations between BF and responses to the lifestyle survey while controlling for known covariates. Results: Lifestyle behaviors explained 8.6% of the total variance in body fat. Specifically, negative associations were found between BF and active transport to school ( β = −0.99 [0.19], P < .001), full-fat milk (−0.07 [0.15], P < .001), and sweetened beverage consumption (−0.40 [0.15], P = .007). Relative to the reference group of ≤8:00 PM, later bedtime was positively associated with BF: 8:00 to 8:59 PM ( β = 1.60 [0.26], P < .001); 9:00 to 10:00 PM ( β = 1.04 [0.24], P < .001); ≥10:00 PM ( β = 1.18 [0.30], P < .001). Two-way interactions revealed opposing associations between BF and the consumption of low-calorie beverages for boys ( β = 0.95 [0.25], P < .001) and girls ( β = −0.85 [0.37], P = .021). There was no significant change in these associations over a 10-year period. Conclusions: In this population-level study covering a decade of data collection, lifestyle behaviors were associated with BF. Policies and interventions targeting population-level behavior change, such as active transport to school, sleep time, and consumption of full-fat milk, may offer an opportunity for improvements in BF.

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Suzanna Russell, Marni J. Simpson, Angus G. Evans, Tristan J. Coulter, and Vincent G. Kelly

Purpose: To investigate and explore the relationships between physiological and perceptual recovery and stress responses to elite netball tournament workloads. Methods: Nine elite female netballers were observed across a 3-day (T1–3), 4-match tournament. Participants provided salivary samples for cortisol and alpha-amylase analysis, completed the Short Recovery Stress Scale (SRSS), and reported session ratings of perceived exertion. Inertial measurement units and heart-rate monitors determined player load, changes of direction (COD), summated heart-rate zones, and jumps. Results: Analysis revealed 6 significant SRSS time effects: (1) decreased recovery markers of physical performance (P = .042), emotional balance (P = .034), and overall recovery (P = .001) and (2) increased perceptual stress markers of muscular stress (P = .001), negative emotional state (P = .026), and overall stress (P = .010). Salivary cortisol decreased over the tournament (T1–3) before progressively increasing posttournament with greater salivary samples for cortisol on T+2 compared with T3 (P = .014, ES = −1.29; −2.24 to −0.22]) and T+1 (P = .031, ES = −1.54; −2.51 to −0.42). SRSS overall recovery moderately negatively correlated with COD (r = −.41, P = .028) and session ratings of perceived exertion (r = −.40, P = .034). Cumulative workload did not relate to posttournament perceptual or salivary responses. Percentage change in salivary variables related (P < .05) to total player load, total COD, and overall recovery across specific cumulative time periods. Conclusions: During and after an elite netball tournament, athletes indicated increased perceptual stress and lack of recovery. The SRSS is a valuable tool for recovery–stress monitoring in elite tournament netball. It is recommended that practitioners monitor COD due to its negative influence on perceived overall recovery.

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Andréa Kruger Gonçalves, Eliane Mattana Griebler, Wagner Albo da Silva, Débora Pastoriza Sant´Helena, Priscilla Cardoso da Silva, Vanessa Dias Possamai, and Valéria Feijó Martins

The objective was to assess the physical fitness of older adults participating in a 5-year multicomponent exercise program. The sample consisted of 138 older adults aged 60–93 years (70.4 ± 7.8 years) evaluated with the Senior Fitness Test (muscle strength, flexibility, balance, and cardiorespiratory fitness). The multicomponent program was carried out between the months of March and November of each year. Data were analyzed using generalized estimating equations (factor year: Year 1, Year 2, Year 3, Year 4, and Year 5; factor time: pretest and posttest) with Bonferroni’s post hoc test. Participation in the multicomponent exercise program for 5 years (baseline pretest Year 1 and follow-up Year 5) improved lower and upper limb strength, lower limb flexibility, and balance and cardiorespiratory fitness, while upper limb flexibility was maintained. Year-by-year analysis revealed variable patterns for each fitness parameter. The results of this study show the potential benefits of implementing a long-term community-based exercise program.

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Alireza Paahoo, Vahid Tadibi, and Nasser Behpoor

Purpose: Atherosclerosis is a complex multifactorial disease whose first steps can be initiated from childhood. Therefore, we examined the effects of 2 training models on salusins levels, inflammatory markers, and lipid profile in boys with overweight/obesity. Method: Forty-five boys with overweight/obesity with the mean age of 11.06 (1.0) years were randomly divided into three groups of 15: a high-intensity interval training (HIIT) group (100%–110% of maximum aerobic speed); an aerobic training group (40%–70% of heart rate reserve); and a control group. The intervention included 3 sessions per week for 12 weeks. Results: Findings showed significant improvements in serum levels of salusins, salusins ratio, interleukin-6 (IL-6), and total cholesterol (TC) in both training groups (P < .001). Also, the serum levels of C-reactive protein (CRP), triglycerides (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), atherogenic index of plasma (AIP), and cholesterol index improved significantly (P < .01). Except for the TG, HIIT caused higher improvements than aerobic training (P < .001 for salusin-α, salusins ratio, IL-6, CRP, TC, HDL, AIP, and cholesterol index; and P < .01 for salusin-β and LDL). Conclusion: The present study shows that HIIT has more positive effects than aerobic exercise on the atherosclerotic and inflammatory factors, as well as lipid profile variables in children with overweight/obesity.

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Cesar L. Teixeira, Paulo V. Mezzaroba, and Fabiana A. Machado

Purpose: To analyze the acute effect of photobiomodulation (PBM) on swimming critical velocity (CV). Methods: A total of 15 male federated swimmers (20.9 [2.4] y old) participated in this study. Three sets of front crawl were performed at distances of 100, 200, and 400 m to determine the CV under 3 experimental conditions: PBM (420 J), placebo (PLA), and control (C) in this randomized, crossover, double-blind, and placebo-controlled study. One-way analysis of variance for repeated measurements was used for statistical analyses. Results: The results showed that the prior application of PBM did not have ergogenic effects on CV and front crawl swimming performance: CV (PBM = 1.15 [0.15]; PLA = 1.20 [0.25]; C = 1.15 [0.14] m·s−1), swim time (ST) 100 m (PBM = 65.5 [6.3]; PLA = 65.2 [5.6]; C = 66.0 [5.9] s), ST 200 m (PBM = 148.5 [17.9]; PLA = 149.4 [16.4]; C = 150.1 [17.9] s), and ST 400 m (PBM = 327.7 [38.2]; PLA = 321.6 [47.7]; C = 329.5 [41.2] s). Conclusions: A PBM application prior to front crawl swimming test did not significantly modify the CV, ST, physiological factors of metabolic fatigue, perceptual, and front crawl stroke efficiency parameters in competition swimmers covering distances of 100, 200, and 400 m.