Purpose: Inconsistent results among studies examining the effects of caffeine on exercise performance are potentially due to interindividual variability in biological responses to caffeine ingestion. The aims, therefore, of the present study were to identify high and low caffeine responders and compare the influence of caffeine on exercise performance and biological responses between groups during a simulated soccer-game protocol on treadmill. Methods: Well-trained soccer players were distinguished as high (n = 11) and low (n = 9) caffeine responders based on resting blood pressure, plasma glycerol, nonesterified fatty acid, and epinephrine responses to caffeine. Participants underwent 2 simulated soccer-game protocols on a treadmill after caffeine (6 mg·kg−1) or placebo ingestion. Exercise performance and several biological responses were evaluated. Results: Exercise performance did not differ between the high and low responders to caffeine (P > .05). However, time to fatigue (high, caffeine: 797  s vs placebo: 487  s; low, caffeine: 625  s vs placebo 447  s) and countermovement jump (high, caffeine: 42.1 [5.5] cm vs placebo: 40.5 [5.7] cm; low, caffeine: 41.0 [3.8] cm vs placebo: 38.8 [4.6] cm) improved with caffeine relative to placebo (P < .001). Rating of perceived exertion was lower (P < .001) in high (13.4 [2.3]) than in low responders (14.3 [2.4]) with caffeine ingestion. Conclusions: Caffeine improved aerobic endurance and neuromuscular performance in well-trained soccer players regardless of their responsiveness to caffeine at rest. Since no changes in substrate utilization were found with caffeine supplementation, performance improvements could be attributed to positive effects on the central nervous system and/or neuromuscular function, although the precise mechanism remains unclear.
Andreas Apostolidis, Vassilis Mougios, Ilias Smilios, Johanna Rodosthenous and Marios Hadjicharalambous
Konstantinos Sotiropoulos, Ilias Smilios, Helen Douda, Marios Christou and Savvas P. Tokmakidis
This study examined the effect of rest interval after the execution of a jump-squat set with varied external mechanical-power outputs on repeated-jump (RJ) height, mechanical power, and electromyographic (EMG) activity.
Twelve male volleyball players executed 6 RJs before and 1, 3, 5, 7, and 10 min after the execution of 6 repetitions of jump squats with a load: maximized mechanical-power output (Pmax), 70% of Pmax, 130% of Pmax, and control, without extra load.
RJ height did not change (P = .44) after the jump squats, mechanical power was higher (P = .02) 5 min after the 130%Pmax protocol, and EMG activity was higher (P = .001) after all exercise protocols compared with control. Irrespective of the time point, however, when the highest RJ set for each individual was analyzed, height, mechanical power, and EMG activity were higher (P = .001–.04) after all loading protocols compared with control, with no differences observed (P = .53–.72) among loads.
Rest duration for a contrast-training session should be individually determined regardless of the load and mechanical-power output used to activate the neuromuscular system. The load that maximizes external mechanical-power output compared with a heavier or a lighter load, using the jump-squat exercise, is not more effective for increasing jumping performance afterward.
Argyris G. Toubekis, Argiro Tsolaki, Ilias Smilios, Helen T. Douda, Thomas Kourtesis and Savvas P. Tokmakidis
To examine the effects of active and passive recovery of various durations after a 100-m swimming test performed at maximal effort.
Eleven competitive swimmers (5 males, 6 females, age: 17.3 ± 0.6 y) completed two 100-m tests with a 15-min interval at a maximum swimming effort under three experimental conditions. The recovery between tests was 15 min passive (PAS), 5 min active, and 10 min passive (5ACT) or 10 min active and 5 min passive (10ACT). Self-selected active recovery started immediately after the first test, corresponding to 60 ± 5% of the 100-m time. Blood samples were taken at rest, 5, 10, and 15 min after the first as well as 5 min after the second 100-m test for blood lactate determination. Heart rate was also recorded during the corresponding periods.
Performance time of the first 100 m was not different between conditions (P > .05). The second 100-m test after the 5ACT (64.49 ± 3.85 s) condition was faster than 10ACT (65.49 ± 4.63 s) and PAS (65.89 ± 4.55 s) conditions (P < .05). Blood lactate during the 15-min recovery period between the 100-m efforts was lower in both active recovery conditions compared with passive recovery (P < .05). Heart rate was higher during the 5ACT and 10ACT conditions compared with PAS during the 15-min recovery period (P < .05).
Five minutes of active recovery during a 15-min interval period is adequate to facilitate blood lactate removal and enhance performance in swimmers. Passive recovery and/or 10 min of active recovery is not recommended.
Ilias Smilios, Konstantinos Sotiropoulos, Karolina Barzouka, Marios Christou and Savvas P. Tokmakidis
This study examined the acute effects of contrast loading on mechanical power output during bench-press throws in junior volleyball players.
Eleven males (age: 16.5 ± 0.5 years) performed a contrast loading and a control protocol. The contrast protocol included the execution of 3 bench-throws with a 30% load of 1RM, after 3 min a conditioning set of 5 bench-throws with a 60% load of 1RM and after 3 and 5 min two more sets of 3 bench-throws with a 30% load of 1RM. The control protocol included the execution of 3 sets of 3 bench-throws with a 30% load of 1RM at the same time points as in the contrast protocol without the execution of the conditioning set.
Mechanical power with a 30% load was higher (p < .05) 3 and 5 min following the conditioning set at the contrast protocol compared with the control protocol (8.7 ± 7.5 and 10.4 ± 3.4%, respectively). High correlations (p < .05) were obtained between participant’s relative maximal strength (r = .87) and power (r = .82) and the increases in power output.
Contrast loading increases upper body power output produced with a light load by junior athletes. The potential for increased upper body performance is more evident in stronger or more powerful individuals.
Helen T. Douda, Konstantina V. Kosmidou, Ilias Smilios, Konstantinos A. Volaklis and Savvas P. Tokmakidis
This five-year follow-up nonrandomized controlled study evaluated community-based training and detraining on body composition and functional ability in older women. Forty-two volunteers (64.3 ± 5.1 years) were divided into four groups: aerobic training, strength training, combined aerobic and strength, and control. Body composition and physical fitness were measured at baseline, after nine months of training and after three months of detraining every year. After five years of training, body fat decreased, and fat free mass, strength, and chair test performance increased (p < .05) in all training groups. Training-induced favorable adaptations were reversed during detraining but, eventually, training groups presented better values than the control group even after detraining. Thus, nine months of annual training, during a five-year period, induced favorable adaptations on body composition, muscular strength, and functional ability in older women. Three months of detraining, however, changed the favorable adaptations and underlined the need for uninterrupted exercise throughout life.