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  • Author: Pavle Mikulic x
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Pavle Mikulic

Purpose:

To examine variations in physical, physiological, and performance parameters over an annual training cycle in a world champion rowing crew.

Methods:

Four world-class rowers, all of them members of the men’s heavyweight quadruple sculls squad who are current world rowing champions, were assessed 3 times at regular 4-mo intervals during the 2011 season (November 2010, March 2011, and July 2011). Physical assessments included stature, body mass, body composition, whereas physiological and performance assessments obtained during an incremental rowing ergometer test to exhaustion included maximum oxygen uptake and anaerobic gas-exchange threshold with corresponding power output values.

Results:

Body mass (∼95 kg) and body composition (∼12% body fat) remained stable over the annual training cycle. Power output at anaerobic gas-exchange threshold increased +16% from November to July, whereas the corresponding oxygen uptake, expressed as a percentage of maximum oxygen uptake, increased from 83% to 90%. Maximum oxygen uptake decreased from 6.68 L/min in November to 6.10 L/min in March before rising to 6.51 L/min in July. The corresponding power output increased steadily from 450 W to 481 W.

Conclusion:

Seasonal variation in body mass and body composition of 4 examined world-class rowers was minimal. Oxygen uptake and power output corresponding to anaerobic threshold continuously increased from off-season to peak competition season. Seasonal variation in maximum oxygen uptake reached ∼10%; however, it remained above 6 L/min, that is, the value consistently observed in top caliber heavyweight rowers regardless of the time of the assessment.

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Filip Sabol, Jozo Grgic and Pavle Mikulic

Purpose: To examine the acute effects of 3 doses of caffeine on upper- and lower-body ballistic exercise performance and to explore if habitual caffeine intake affects the acute effects of caffeine ingestion on ballistic exercise performance. Methods: Twenty recreationally active male participants completed medicine-ball-throw and vertical-jump tests under 4 experimental conditions (placebo and 2, 4, and 6 mg·kg−1 of caffeine). Results: One-way repeated-measures analysis of variance (ANOVA) with subsequent post hoc analyses indicated that performance in the medicine-ball-throw test improved, compared with placebo, only with a 6 mg·kg−1 dose of caffeine (P = .032). Effect size, calculated as the mean difference between the 2 measurements divided by the pooled SD, amounted to 0.29 (+3.7%). For the vertical-jump test, all 3 caffeine doses were effective (compared with placebo) for acute increases in performance (P values .022–.044, effect sizes 0.35–0.42, percentage changes +3.7% to +4.1%). A 2-way repeated-measures ANOVA indicated that there was no significant group × condition interaction effect, suggesting comparable responses between low (≤100 mg·d−1) and moderate to high (>100 mg·d−1) caffeine users to the experimental conditions. Conclusion: Caffeine doses of 2, 4, and 6 mg·kg−1 seem to be effective for acute enhancements in lower-body ballistic exercise performance in recreationally trained male individuals. For the upper-body ballistic exercise performance, only a caffeine dose of 6 mg·kg−1 seems to be effective. The acute effects of caffeine ingestion do not seem to be affected by habitual caffeine intake; however, this requires further exploration.

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Sandro Venier, Jozo Grgic and Pavle Mikulic

Purpose: To explore the acute effects of caffeinated chewing gum on vertical-jump performance, isokinetic knee-extension/flexion strength and power, barbell velocity in resistance exercise, and whole-body power. Methods: Nineteen resistance-trained men consumed, in randomized counterbalanced order, either caffeinated chewing gum (300 mg of caffeine) or placebo and completed exercise testing that included squat jump; countermovement jump; isokinetic knee extension and knee flexion at angular velocities of 60 and 180°·s−1; bench-press exercise with loads corresponding to 50%, 75%, and 90% of 1-repetition maximum (1RM); and an “all-out” rowing-ergometer test. Results: Compared with placebo, caffeinated chewing gum enhanced (all Ps < .05) (1) vertical-jump height in the squat jump (effect size [ES] = 0.21; +3.7%) and countermovement jump (ES = 0.27; +4.6%); (2) knee-extension peak torque (ES = 0.21; +3.6%) and average power (ES = 0.25; +4.5%) at 60°·s−1 and knee-extension average power (ES = 0.30; +5.2%) at 180°·s−1, and knee-flexion peak torque at 60°·s−1 (ES = 0.22; +4.1%) and 180°·s−1 (ES = 0.31; +5.9%); (3) barbell velocity at 50% of 1RM (ES = 0.30; +3.2%), 75% of 1RM (ES = 0.44; +5.7%), and 90% of 1RM (ES = 0.43; +9.1%); and (4) whole-body peak power on the rowing-ergometer test (ES = 0.41; +5.0%). Average power of the knee flexors did not change at either angular velocity with caffeine consumption. Conclusions: Caffeinated chewing gum with a dose of caffeine of 300 mg consumed 10 min preexercise may acutely enhance vertical-jump height, isokinetic strength and power of the lower-body musculature, barbell velocity in the bench-press exercise with moderate to high loads, and whole-body power.

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Pavle Mikulic, Tomislav Blazina, Alan M. Nevill and Goran Markovic

The purpose of the current study was to examine the effect of age and body size upon maximal-intensity exercise performance in young rowing athletes. Male participants n = 171) aged 12–18 years were assessed using an “all-out” 30-s rowing ergometer test, and reassessed after 12 months. The highest rate of performance development, which amounts to [mean(SD)] +34%(23%) and +32%(23%) for mean and maximal power output, respectively, is observed between the ages of 12 and 13, while this rate of development gradually declines as the athletes mature through adolescence. Performance increases with body size, and mass, stature and chronological age all proved to be significant (all p < .05) explanatory variables of mean power output, with respective exponents [mean(SE)] of 0.56(0.08), 1.84(0.30) and 0.07(0.01), and of maximal power output, with respective exponents of 0.54(0.09), 1.76(0.32) and 0.06(0.01). These findings may help coaches better understand the progression of rowing performance during adolescence.

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Jozo Grgic, Filip Sabol, Sandro Venier, Ivan Mikulic, Nenad Bratkovic, Brad J. Schoenfeld, Craig Pickering, David J. Bishop, Zeljko Pedisic and Pavle Mikulic

Purpose: To explore the effects of 3 doses of caffeine on muscle strength and muscle endurance. Methods: Twenty-eight resistance-trained men completed the testing sessions under 5 conditions: no-placebo control, placebo control, and with caffeine doses of 2, 4, and 6 mg·kg−1. Muscle strength was assessed using the 1-repetition-maximum test; muscle endurance was assessed by having the participants perform a maximal number of repetitions with 60% 1-repetition maximum. Results: In comparison with both control conditions, only a caffeine dose of 2 mg·kg−1 enhanced lower-body strength (d = 0.13–0.15). In comparison with the no-placebo control condition, caffeine doses of 4 and 6 mg·kg−1 enhanced upper-body strength (d = 0.07–0.09) with a significant linear trend for the effectiveness of different doses of caffeine (P = .020). Compared with both control conditions, all 3 caffeine doses enhanced lower-body muscle endurance (d = 0.46–0.68). For upper-body muscle endurance, this study did not find significant effects of caffeine. Conclusions: This study revealed a linear trend between the dose of caffeine and its effects on upper-body strength. The study found no clear association between the dose of caffeine and the magnitude of its ergogenic effects on lower-body strength and muscle endurance. From a practical standpoint, the magnitude of caffeine’s effects on strength is of questionable relevance. A low dose of caffeine (2 mg·kg−1)—for an 80-kg individual, the dose of caffeine in 1–2 cups of coffee—may produce substantial improvements in lower-body muscle endurance with the magnitude of the effect being similar to that attained using higher doses of caffeine.