Browse

You are looking at 1 - 10 of 24,872 items

Restricted access

Michal Wilk, Michal Krzysztofik, Milosz Drozd and Adam Zajac

Purpose: Resistance training is one of the key components influencing power output. Previous studies directed at power development through the use of postactivation potentiation have analyzed resistance exercises at volitional or fast tempo of movement in the entire cycle, without control of the duration of the concentric and eccentric phases of movement. To date, no scientific studies have explored the effects of varied movement tempo on the level of power output, velocity, and postactivation potentiation efficiency. Methods: During the experimental sessions, study participants performed 3 sets (Sets1–3) of the bench-press exercise using 70% 1-repetition maximum and 2 different tempos of movement: 2/0/X/0 eccentric medium tempo (ECCMED) and 6/0/X/0 eccentric slow tempo (ECCSLO). Results: Post hoc analysis demonstrated significant differences in values of peak (P PEAK) and mean (P MEAN) power between Sets1–3 measured for the ECCMED (2/0/X/0) tempo. The values of P MEAN in Set3 (492.15 [87.61] W) were significantly higher than in Set2 (480.05 [82.10] W) and Set1 (467.65 [79.18] W). Similarly, the results of P PEAK in Set3 (713.10 [132.72] W) were significantly higher than those obtained in Set2 (702.25 [129.5] W) and Set1 (671.55 [115.79] W). For the ECCSLO tempo (6/0/X/0) in Set2 (587.9 [138.48] W), the results of P PEAK were significantly higher than in Set1 (565.7 [117.37] W) and Set3 (563.1 [124.93] W). Conclusions: The results of this study indicate that the postactivation potentiation effect is observed for both slow and medium tempos of movement.

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

Joseph Hamill

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

John Wong and Scott R. Jedlicka

In 1966, the National Hockey League (NHL) expanded for the first time since the 1920s, doubling its size from six teams to twelve. Although hockey was still perceived as a distinctly Canadian passion, none of the NHL’s six new teams were located in Canada. The disappointment across the country was palpable, especially in Canada’s third-largest city, Vancouver, which had applied to be one of the expansion locations. A stable presence in minor league hockey on Canada’s west coast for decades, it seemed only natural that Vancouver, as the lone bidder from the ostensible birthplace of ice hockey, would be tapped for NHL expansion. This paper examines Vancouver’s attempted entry into the NHL and argues that the forces of commercialism and national identity, combined with political maneuvering among NHL owners, not only influenced the content and trajectory of the Vancouver bid, but also contributed to its ultimate failure.

Restricted access

Ibrahim M. Altubasi

The purposes of this study were first to examine the association between aging and both the magnitude and asymmetry in the femoral neck-shaft angle (NSA). The second purpose was to determine the effects of both the magnitude and NSA asymmetry on the performance of functional activities in healthy individuals. Fifty-one subjects participated in this study. The femoral NSA was measured on computed tomography scout images. The participants performed four performance tests. Four hierarchical regression models were constructed to explore the effect of each predictor on the outcomes. Aging was associated with NSA asymmetry, but not with the degree of NSA. Age contributed significantly to the variability of all functional performance tests except the 10-m walking speed. The degree of the NSA did not contribute to the prediction of the functional performance tests. However, asymmetry in the NSA added significantly to the prediction of all functional performance tests except the 10-m walking speed.

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.