Browse

You are looking at 21 - 30 of 4,483 items for :

  • Sport and Exercise Science/Kinesiology x
  • Physical Education and Coaching x
Clear All
Restricted access

Helen G. Hanstock, Andrew D. Govus, Thomas B. Stenqvist, Anna K. Melin, Øystein Sylta and Monica K. Torstveit

Intensive training periods may negatively influence immune function, but the immunological consequences of specific high-intensity-training (HIT) prescriptions are not well defined. Purpose: To explore whether 3 different HIT prescriptions influence multiple health-related biomarkers and whether biomarker responses to HIT were associated with upper-respiratory-illness (URI) risk. Methods: Twenty-five male cyclists and triathletes were randomized to 3 HIT groups and completed 12 HIT sessions over 4 wk. Peak oxygen consumption (V˙O2peak) was determined using an incremental cycling protocol, while resting serum biomarkers (cortisol, testosterone, 25[OH]D, and ferritin), salivary immunoglobulin-A (s-IgA), and energy availability (EA) were assessed before and after the training intervention. Participants self-reported upper-respiratory symptoms during the intervention, and episodes of URI were identified retrospectively. Results: Fourteen athletes reported URIs, but there were no differences in incidence, duration, or severity between groups. Increased risk of URI was associated with higher s-IgA secretion rates (odds ratio = 0.90, 90% confidence interval 0.83–0.97). Lower preintervention cortisol and higher EA predicted a 4% increase in URI duration. Participants with higher V˙O2peak reported higher total symptom scores (incidence rate ratio = 1.07, 90% confidence interval 1.01–1.13). Conclusions: Although multiple biomarkers were weakly associated with risk of URI, the direction of associations between s-IgA, cortisol, EA, and URI risk were inverse to previous observations and physiological rationale. There was a cluster of URIs in the first week of the training intervention, but no samples were collected at this time point. Future studies should incorporate more-frequent sample time points, especially around the onset of new training regimens, and include athletes with suspected or known nutritional deficiencies.

Restricted access

David C. Nieman, Giuseppe Valacchi, Laurel M. Wentz, Francesca Ferrara, Alessandra Pecorelli, Brittany Woodby, Camila A. Sakaguchi and Andrew Simonson

This double-blinded, placebo controlled, randomized crossover trial investigated the influence of 2-week mixed flavonoid versus placebo supplementation on oxinflammation markers after a 75-km cycling time trial in 22 cyclists (42.3 ± 1.7 years). Blood samples were collected before and after the 2-week supplementation, and then 0 hr, 1.5 hr, and 21 hr post 75-km cycling (176 ± 5.4 min, 73.4 ±2.0% maximal oxygen consumption). The supplement provided 678-mg flavonoids with quercetin (200 mg), green tea catechins (368 mg, 180-mg epigallocatechin gallate), and anthocyanins (128 mg) from bilberry extract, with caffeine, vitamin C, and omega-3 fatty acids added as adjuvants. Blood samples were analyzed for blood leukocyte counts, oxinflammation biomarkers, including 4-hydroxynonenal, protein carbonyls, and peripheral blood mononuclear mRNA expression for cyclooxygenease-2 and glutathione peroxidase. Each of the blood biomarkers was elevated postexercise (time effects, all ps < .01), with lower plasma levels for 4-hydroxynonenal (at 21-hr postexercise) in flavonoid versus placebo (interaction effect, p = .008). Although elevated postexercise, no trial differences for the neutrophil/lymphocyte ratio (p = .539) or peripheral blood mononuclear mRNA expression for cyclooxygenease-2 (p = .322) or glutathione peroxidase (p = .839) were shown. Flavonoid supplementation prior to intensive exercise decreased plasma peroxidation and oxidative damage, as determined by 4-hydroxynonenal. Postexercise increases were similar between the flavonoid and placebo trials for peripheral blood mononuclear mRNA expression for cyclooxygenease-2 and the nuclear factor erythroid 2-related factor 2 related gene glutathione peroxidase (NFE2L2). The data support the strategy of flavonoid supplementation to mitigate postexercise oxidative stress in endurance athletes.

Restricted access

Theofanis Tzatzakis, Konstantinos Papanikolaou, Dimitrios Draganidis, Panagiotis Tsimeas, Savvas Kritikos, Athanasios Poulios, Vasiliki C. Laschou, Chariklia K. Deli, Athanasios Chatzinikolaou, Alexios Batrakoulis, Georgios Basdekis, Magni Mohr, Peter Krustrup, Athanasios Z. Jamurtas and Ioannis G. Fatouros

Purpose: To determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. Methods: Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72 h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3 h posttraining. Results: Fatigue increased (P < .05) in SEPT/1:5 (∼4–30%) for 3 h and in SEPT/1:8 (∼8–17%) for 2 h. Strength performance declined (P < .05) in both SEPT trials (∼5–20%) for 48 h. Speed decreased (∼4–18%; P < .05) for 72 h in SEPT/1:5 and for 48 h in SEPT/1:8. Countermovement-jump performance decreased (∼7–12%; P < .05) in both SEPT trials for 24 h. DOMS increased (P < .05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48 h. Creatine kinase increased (∼1- to 2-fold, P < .05) in both SEPT trials for 72 h. Conclusions: SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48 h), speed (72 h), and jump performance (24 h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics.

Restricted access

Cruz Hogan, Martyn J. Binnie, Matthew Doyle, Leanne Lester and Peter Peeling

Purpose: To compare methods of monitoring and prescribing on-water exercise intensity (heart rate [HR], stroke rate [SR], and power output [PO]) during sprint kayak training. Methods: Twelve well-trained flat-water sprint kayak athletes completed a preliminary on-water 7 × 4-min graded exercise test and a 1000-m time trial to delineate individual training zones for PO, HR, and SR into a 5-zone model (T1–T5). Subsequently, athletes completed 2 repeated trials of an on-water training session, where intensity was prescribed based on individual PO zones. Times quantified for T1–T5 during the training session were then compared between PO, HR, and SR. Results: Total time spent in T1 was higher for HR (P < .01) compared with PO. Time spent in T2 was lower for HR (P < .001) and SR (P < .001) compared with PO. Time spent in T3 was not different between PO, SR, and HR (P > .05). Time spent in T4 was higher for HR (P < .001) and SR (P < .001) compared with PO. Time spent in T5 was higher for SR (P = .03) compared with PO. Differences were found between the prescribed and actual time spent in T1–T5 when using PO (P < .001). Conclusions: The measures of HR and SR misrepresented time quantified for T1–T5 as prescribed by PO. The stochastic nature of PO during on-water training may explain the discrepancies between prescribed and actual time quantified for power across these zones. For optimized prescription and monitoring of athlete training loads, coaches should consider the discrepancies between different measures of intensity and how they may influence intensity distribution.

Restricted access

Mostafa Zarei, Hamed Abbasi, Abdolhamid Daneshjoo, Mehdi Gheitasi, Kamran Johari, Oliver Faude, Nikki Rommers and Roland Rössler

Purpose: The “11+ Kids” injury-prevention program has been shown to reduce injuries and related costs in youth football players less than 14 y of age. A major argument to convince coaches to use this exercise-based injury-prevention program is a potential performance enhancement of the players. Therefore, this study investigated the effects of the “11+ Kids” program on isokinetic strength. Methods: Two teams were randomly assigned to the intervention and control groups. The intervention group replaced their warm-up by the “11+ Kids” and the control group warmed up as usual. Two days before and after the 10-wk intervention, isokinetic strength of the hip adductors and abductors, knee flexors and extensors, and ankle invertors and evertors was tested. Results: Thirty-one players (mean age 11.5 [0.8] y) completed the study. The intervention group showed large improvements in all isokinetic strength measures (P < .001 for all measures; Cohen d = 0.8–1.4), whereas the control group only showed negligible to medium positive effects (P values ranging from .006 to .718; Cohen d = −0.1 to 0.7). The intervention was beneficial compared with the control group regarding isokinetic strength of the hip adductors (P < .001), knee flexors (P = .002), and ankle evertors (P < .001) and invertors (P = .005). Conclusions: Given the relatively short intervention period of 10 wk, the observed improvements relate to a practically meaningful effect of the intervention. The gain in strength may improve players’ performance and may contribute to a reduction of injury risk in the long-term application.

Restricted access

Ana Gay, Gracia López-Contreras, Ricardo J. Fernandes and Raúl Arellano

Purpose: To observe changes in performance, physiological, and general kinematic variables induced by the use of wetsuits vs swimsuits in both swimming-pool and swimming-flume conditions. Methods: In a randomized and counterbalanced order, 33 swimmers (26.46 [11.72] y old) performed 2 × 400-m maximal front crawl in a 25-m swimming pool (with wetsuit and swimsuit), and their mean velocities were used later in 2 swimming-flume trials with both suits. Velocity, blood lactate concentration, heart rate (HR), Borg scale (rating of perceived exertion), stroke rate, stroke length (SL), stroke index, and propelling efficiency were evaluated. Results: The 400-m performance in the swimming pool was 0.07 m·s−1 faster when using the wetsuit than when using the swimsuit, evidencing a reduction of ∼6% in time elapsed (P < .001). Maximal HR, maximal blood lactate concentration, rating of perceived exertion, stroke rate, and propelling efficiency were similar when using both swimsuits, but SL and stroke index presented higher values with the wetsuit in both the swimming pool and the swimming flume. Comparing swimming conditions, maximal HR and maximal blood lactate concentration were lower, and SL, stroke index, and propelling efficiency were higher when swimming in the flume than when swimming in the pool with both suits. Conclusions: The 6% velocity improvement was the result of an increase of 4% in SL. Swimmers reduced stroke rate and increased SL to benefit from the hydrodynamic reduction of the wetsuit and increase their swimming efficiency. Wetsuits might be utilized during training seasons to improve adaptations while swimming.

Restricted access

Lucas A. Pereira, Rodrigo Ramirez-Campillo, Saul Martín-Rodríguez, Ronaldo Kobal, César C.C. Abad, Ademir F.S. Arruda, Aristide Guerriero and Irineu Loturco

Purpose: To examine the variations in the velocity of contraction (V c) assessed using tensiomyography, vertical jumping ability, and sprinting speed induced by 4 different exercise protocols (ie, strength, sprint, plyometric, and technical training sessions) in 14 male national-team rugby players (age 21.8 [2.6] y, weight 83.6 [8.5] kg, and height 177.4 [6.7] cm). Methods: Physical tests were conducted immediately before and after 4 distinct workouts in the following order: tensiomyography in the rectus femoris and biceps femoris muscles, squat and countermovement jumps, and 30-m sprint velocity. To analyze the differences in the assessed variables before and after each training session, the differences based on magnitudes were calculated. Results: After strength and plyometric workouts, the players presented possible to almost certain impairments in sprint and jump performance and in the V c of the rectus femoris (effect sizes 0.26–0.64). After the sprint-training session, possible to very likely decreases were observed in the squat jump, 30-m sprint, and V c of the biceps femoris (effect sizes 0.21–0.44). By contrast, after the technical training, athletes demonstrated a possible increase in the squat jump and V c in both muscles examined (effect sizes 0.13–0.20). Conclusions: The main finding of this research is that, for the vast majority of results, the direction of changes observed in V c were the same as those observed in performance assessments. This suggests that V c might be used as a sensitive marker of acute variations in speed and power performance of elite team-sport athletes.

Restricted access

Claire J. Brady, Andrew J. Harrison, Eamonn P. Flanagan, G. Gregory Haff and Thomas M. Comyns

Purpose: To examine the relationships between the isometric midthigh pull (IMTP), isometric squat (ISqT), and sprint acceleration performance in track-and-field sprinters and to determine whether there are differences between men and women. Methods: Fifteen male and 10 female sprinters performed 3 maximal-effort IMTPs, ISqTs, and 3 × 30-m sprints from blocks. Results: Among the men, the results showed significant negative correlations between IMTP and ISqT peak force; relative peak force; force at 100, 150, and 200 ms; rate of force development (0–150 and 0–200 ms); and impulse (0–200 ms) and 0- to 5-m time (r = −.517 to −.714; P < .05). IMTP impulse (B = −0.582, P = .023) and ISqT relative peak force (B = −0.606, P = .017) significantly predicted 0- to 5-m time. Among the women, no IMTP or ISqT variables significantly correlated with any sprint times. Men measured significantly higher than women for all IMTP measures except relative peak force. Men were significantly faster than women at all splits. When comparing measures of the ISqT, there were no significant differences between men and women. Conclusions: Variables measured during the IMTP and ISqT significantly correlated with 0- to 5-m sprint performance in male athletes. Isometric strength can have a sizable influence on 0- to 5-m time, but in some cases, the maximum effect could be very small.

Restricted access

Marco Beato, Stuart A. McErlain-Naylor, Israel Halperin and Antonio Dello Iacono

Purpose: To summarize the evidence on postactivation potentiation (PAP) protocols using flywheel eccentric overload (EOL) exercises. Methods: Studies were searched using the electronic databases PubMed, Scopus, and Institute for Scientific Information Web of Knowledge. Results: In total, 7 eligible studies were identified based on the following results: First, practitioners can use different inertia intensities (eg, 0.03–0.88 kg·m2), based on the exercise selected, to enhance sport-specific performance. Second, the PAP time window following EOL exercise seems to be consistent with traditional PAP literature, where acute fatigue is dominant in the early part of the recovery period (eg, 30 s), and PAP is dominant in the second part (eg, 3 and 6 min). Third, as EOL exercises require large force and power outputs, a volume of 3 sets with the conditioning activity (eg, half-squat or lunge) seems to be a sensible approach. This could reduce the transitory muscle fatigue and thereby allow for a stronger potentiation effect compared with larger exercise volumes. Fourth, athletes should gain experience by performing EOL exercises before using the tool as part of a PAP protocol (3 or 4 sessions of familiarization). Finally, the dimensions of common flywheel devices offer useful and practical solutions to induce PAP effects outside of normal training environments and prior to competitions. Conclusions: EOL exercise can be used to stimulate PAP responses to obtain performance advantages in various sports. However, future research is needed to determine which EOL exercise modalities among intensity, volume, and rest intervals optimally induce the PAP phenomenon and facilitate transfer effects on athletic performances.

Restricted access

Jonathon J.S. Weakley, Dale B. Read, Hugh H.K. Fullagar, Carlos Ramirez-Lopez, Ben Jones, Cloe Cummins and John A. Sampson

Purpose: To investigate whether providing global positioning system feedback to players between bouts of small-sided games (SSGs) can alter locomotor, physiological, and perceptual responses. Methods: Using a reverse counterbalanced design, 20 male university rugby players received either feedback or no feedback during “off-side” touch rugby SSGs. Eight 5v5, 6 × 4-minute SSGs were played over 4 d. Teams were assigned to a feedback or no-feedback condition (control) each day, with feedback provided during the 2-min between-bouts rest interval. Locomotor, heart rate, and differential rating of perceived exertion of breathlessness and leg-muscle exertion were measured and analyzed using a linear mixed model. Outcomes were reported using effect sizes (ES) and 90% confidence intervals (CI), and then interpreted via magnitude-based decisions. Results: Very likely trivial to unclear differences at all time points were observed in heart rate and differential rating of perceived exertion measures. Possibly to very likely trivial effects were observed between conditions, including total distance (ES = 0.15; 90 CI, −0.03 to 0.34), high-speed distance (ES = −0.07; 90 CI, −0.27 to 0.13), and maximal sprint speed (ES = 0.11; 90% CI, −0.11 to 0.34). All within-bout comparisons showed very likely to unclear differences, apart from possible increases in low-speed distance in bout 2 (ES = 0.23; 90% CI, 0.01 to 0.46) and maximal sprint speed in bout 4 (ES = 0.21; 90% CI, −0.04 to 0.45). Conclusions: In this study, verbal feedback did not alter locomotor, physiological, or perceptual responses in rugby players during SSGs. This may be due to contextual factors (eg, opposition) or the type (ie, distance) or low frequency of feedback provided.