Bernardo Requena

Does plyometric training improve strength performance? A meta-analysis.

Majority of the research suggests plyometric training (PT) improves maximal strength performance as measured by 1RM, isometric MVC or slow velocity isokinetic testing. However, the effectiveness of PT depends upon various factors. A meta-analysis of 15 studies with a total of 31 effect sizes (ES) was carried out to analyse the role of various factors on the effects of PT on strength performance. The inclusion criteria for the analysis were: (a) studies using PT programs for lower limb muscles; (b) studies employing true experimental design and valid and reliable measurements; (c) studies including sufficient data to calculate ES. When subjects can adequately follow plyometric exercises, the training gains are independent of fitness level. Subjects in either good or poor physical condition, benefit equally from plyometric work, also men obtain similar strength results to women following PT. In relation to the variables of program design, training volume of less than 10 weeks and with more than 15 sessions, as well as the implementation of high-intensity programs, with more than 40 jumps per session, were the strategies that seem to maximize the probability to obtain significantly greater improvements in performance (p<0.05). In order to optimise strength enhancement, the combination of different types of plyometrics with weight-training would be recommended, rather than utilizing only one form (p<0.05). The responses identified in this analysis are essential and should be considered by the strength and conditioning professional with regard to the most appropriate dose-response trends for PT to optimise strength gains.

Sodium bicarbonate and sodium citrate: ergogenic aids?

Numerous studies have used exogenous administration of sodium bicarbonate (NaHCO(3)) and sodium citrate (Na-citrate) in an attempt to enhance human performance. After ingestion of NaHCO(3) and Na-citrate, two observations have been made: (a) There was great individual variability in the ergogenic benefit reached, which can be attributed to the level of physical conditioning of the subjects and to their tolerance of the buffer substance; and (b) the subjects who had ingested NaHCO(3) and Na-citrate show higher levels of pH, bicarbonate, and lactate ions concentrations in their exercising blood than do the subjects who had ingested the placebo. A majority of the studies have suggested that the ingestion of both substances provides an ergogenic effect due to the establishment and maintenance of an elevated pH level during exercise. However, the exact mechanism by which the ergogenic effects occur has not been demonstrated conclusively. Sodium bicarbonate and Na-citrate seem to be effective in activities with a sufficient duration to generate a difference in the hydrogen ion gradient, characterized by a very high intensity and involving large muscular groups. However, in activities of equally high intensity, but with longer duration, the results obtained have been conflicting and inconclusive.

The Effects of Plyometric Training on Sprint Performance: A Meta-analysis

Sáez de Villarreal, E, Requena, B, and Cronin, JB. The effects of plyometric training on sprint performance. A meta-analysis. J Strength Cond Res 26(2): 575–584, 2012—The purpose of this meta-analysis was to attempt to gain a clear picture of the magnitude of sprint performance improvements expected after chronic plyometric training (PT) and to identify specific factors that influence the treatment effects. Studies employing a PT intervention and containing data necessary to calculate effect size (ES) were included in the analysis. A total of 26 studies with a total of 56 ES met the inclusion criterion. Analysis of ES demonstrated that the strategies that seem to maximize the probability of obtaining significantly (p < 0.05) greater improvement in sprint performance included training volume for <10 weeks; a minimum of 15 sessions; and high-intensity programs with >80 combined jumps per session. To optimize sprint enhancement, the combination of different types of plyometrics and the use of training programs that incorporate greater horizontal acceleration (i.e., sprint-specific plyometric exercises, jumps with horizontal displacement) would be recommended, rather than using only one form of jump training (p < 0.05). No extra benefits were found to be gained from doing plyometrics with added weight. The loading parameters identified in this analysis should be considered by the professional sprinters and specialized trainers with regard to the most appropriate dose-response trends PT to optimized sprint performance gains.

Functional Performance, Maximal Strength, and Power Characteristics in Isometric and Dynamic Actions of Lower Extremities in Soccer Players

Requena, B, González-Badillo, JJ, Saez de Villareal, ES, Ereline, J, García, I, Gapeyeva, H, and Pääsuke, M. Functional performance, maximal strength, and power characteristics in isometric and dynamic actions lower extremities in soccer players. J Strength Cond Res 23(5): 1391-1401, 2009-The purposes of the present study were to determine muscle strength and power output characteristics in a group of professional soccer players and to identify their relationships with 2 functional performance tests (vertical jumping height and 15-m sprint time). Maximal strength and power indices attained against different loads in barbell back squat exercise, isometric maximal force of the knee extensor and plantar flexor muscles, isokinetic peak torque of the knee extensors muscles, vertical jumping height in squat and counter-movement jumps, and 15-m sprint time tests were assessed in 21 semiprofessional soccer players (age 20 ± 3.8 years). Correlation analyses were performed to examine the relationship between each of these measures. The main results of the present study were that (a) maximal power in concentric half-squat exercise was attained with a load of 60% of 1 repetition maximum, representing 112% of body weight; (b) the performance in the functional tests selected was significantly related with all the half-squat variables measured, especially with loads of 75-125% of body weight; and (c) low to nonsignificant correlations were found between functional tests performance and isometric and isokinetic muscle strength measures. It was concluded that in semiprofessional soccer players (a) isometric and isokinetic muscle strength assessed in an open kinetic chain were not movement-specific enough to predict performance during a more complex movement, such as jump or sprint and (b) concentric half-squat exercise was principally related with the functional tests selected when it was performed against external loading within the range of the load in case of which the maximal power output was attained.

Positional Differences in Match Running Performance and Physical Collisions in Men Rugby Sevens

PURPOSE This study describes the physical match demands relative to positional group in male rugby sevens. METHODS Ten highly trained players were investigated during competitive matches (N = 23) using GPS technology, heart rate (HR), and video recording. RESULTS The relative distance covered by the players throughout the match was 102.3 ± 9.8 m/min. As a percentage of total distance, 35.8% (36.6 ± 5.9 m/min) was covered walking, 26.0% (26.6 ± 5.5 m/min) jogging, 10.0% (10.2 ± 2.4 m/min) running at low intensity, 14.2% (14.5 ± 4.0 m/min) at medium intensity, 4.6% (4.7 ± 1.6 m/min) at high intensity, and 9.5% (9.7 ± 3.7 m/min) sprinting. For the backs, a substantial decrease in total distance and distance covered at low, medium, and high intensity was observed in the second half. Forwards exhibited a substantial decrease in the distance covered at medium intensity, high intensity, and sprinting in the 2nd half. Backs covered substantially more total distance at medium and sprinting speeds than forwards. In addition, the maximum length of sprint runs was substantially greater for the backs than forwards. On the contrary, forwards performed more tackles. The mean HR during the match in backs and forwards was similar, with the exception of time spent at HR intensities >90%HRmax, which was substantially higher in forwards. CONCLUSION These findings provide a description of the different physical demands placed on rugby sevens backs and forwards. This information may be helpful in the development of positional and/or individualized physical-fitness training programs.

Enhancing sprint and strength performance: Combined versus maximal power, traditional heavy-resistance and plyometric training

OBJECTIVES This study compares the effect of five different training stimuli on sprinting ability and strength production. DESIGN Sixty physical education students were randomly assigned to five experimental groups: all types of training (A), full-squat (B), parallel-squat (C), loaded countermovement jumping (D) and plyometric training (E). Participants in each group trained three days a week for a total of seven weeks. METHODS Sprint performance (30m), maximal dynamic strength (1RM) (kg) and velocity of displacement in the concentric phase of full-squat (m/s) were measured before and after seven weeks of training. RESULTS Pre-training results showed no significant differences among the groups in any of the variables tested. After seven weeks no significant improvement in sprint performance was found, however, significant improvement in maximal dynamic strength, velocity of displacement were observed in all the groups: combined methods group A (20%), heavy-resistance group B (11%), power-oriented group C (17%), ballistic group D (14%) and plyometric group E (6%). CONCLUSIONS A combined training approach using full-squat, parallel-squat, loaded countermovement jumping and plyometric training results in a light improvement in maximal strength, velocity of displacement and sprint performance and the resemblance between movement patterns and the velocity of displacement common to the training and testing methods also contributes to greater performance improvement.

RELATIONSHIP BETWEEN POSTACTIVATION POTENTIATION OF KNEE EXTENSOR MUSCLES, SPRINTING AND VERTICAL JUMPING PERFORMANCE IN PROFESSIONAL SOCCER PLAYERS

Requena, B, de Villarreal, ESS, Gapeyeva, H, Ereline, J, García, I, and Pääsuke, M. Relationship between postactivation potentiation of knee extensor muscles, sprinting and vertical jumping performance in professional soccer players. J Strength Cond Res 25(2): 367-373, 2011-Little is known about the relationship between postactivation potentiation (PAP) in human muscles, assessed by enhancement of twitch torque after a conditioning maximal voluntary contraction (MVC), and performance in activities requiring power and speed. Moreover, no studies have assessed PAP in soccer players who train power and endurance simultaneously. The purpose of the present study was to examine the relationship between twitch PAP in knee extensor (KE) muscles, and sprinting and vertical jumping performance in soccer players. Fourteen professional male soccer players with mean (SD) age 20.0 (3.6) years, height 177.9 (6.9) cm and body mass 70.5 (5.7) kg) were tested for 15-m sprint time, vertical jump height in countermovement (CMJ) and squat (SJ) jumps. PAP in KE muscles was induced by a 10-s isometric MVC. Electrically evoked twitches of KE muscles were evoked before and after the conditioning MVC. Immediately after the conditioning MVC, twitch peak torque (PT) and maximal rates of torque development and relaxation were significantly potentiated. A significant negative correlation was found between 15-m sprint time and jump height in CMJ (r = −0.63) and SJ (r = −0.57). PAP of twitch PT correlated significantly positively with jump height in CMJ (r = 0.61) and SJ (r = 0.64), and negatively with 15-m sprint time (r = −0.59). In conclusion, twitch PAP in KE muscles was significantly correlated with performance in vertical jumping and sprinting in male professional soccer players, whereas the magnitude of PAP in soccer players was similar to that observed previously in power-trained athletes.

Effects of sodium bicarbonate ingestion on performance and perceptual responses in a laboratory-simulated BMX cycling qualification series.

Zabala, M, Requena, B, Sánchez-Muñoz, C, González-Badillo, JJ, García, I, Ööpik, V, and Pääsuke, M. Effects of sodium bicarbonate ingestion on performance and perceptual responses in a laboratory-simulated BMX cycling qualification series. J Strength Cond Res 22(5): 1645-1653, 2008-The objective of this study was to examine the effect of sodium bicarbonate (NaHCO3−) ingestion on performance and perceptual responses in a laboratory-simulated bicycle motocross (BMX) qualification series. Nine elite BMX riders volunteered to participate in this study. After familiarization, subjects undertook two trials involving repeated sprints (3 × Wingate tests [WTs] separated by 30 minutes of recovery; WT1, WT2, WT3). Ninety minutes before each trial, subjects ingested either NaHCO3− or placebo in a counterbalanced, randomly assigned, double-blind manner. Each trial was separated by 4 days. Performance variables of peak power, mean power, time to peak power, and fatigue index were calculated for each sprint. Ratings of perceived exertion were obtained after each sprint, and ratings of perceived readiness were obtained before each sprint. No significant differences were observed in performance variables between successive sprints or between trials. For the NaHCO3− trial, peak blood lactate during recovery was greater after WT2 (p < 0.05) and tended to be greater after WT3 (p = 0.07), and ratings of perceived exertion were not influenced. However, improved ratings of perceived readiness were observed before WT2 and WT3 (p < 0.05). In conclusion, NaHCO3− ingestion had no effect on performance and RPE during a series of three WT simulating a BMX qualification series, possibly because of the short duration of each effort and the long recovery time used between the three WTs. On the contrary, NaHCO3− ingestion improved perceived readiness before each WT.

Relationship between traditional and ballistic squat exercise with vertical jumping and maximal sprinting.

Requena, B, García, I, Requena, F, Sáez-Sáez de Villarreal, E, and Cronin, JB. Relationship between traditional and ballistic squat exercise with vertical jumping and maximal sprinting. J Strength Cond Res 25(8): 2193-2204, 2011—The purpose of this study was to quantify the magnitude of the relationship between vertical jumping and maximal sprinting at different distances with performance in the traditional and ballistic concentric squat exercise in well-trained sprinters. Twenty-one men performed 2 types of barbell squats (ballistic and traditional) across different loads with the aim of determining the maximal peak and average power outputs and 1 repetition maximum (1RM) values. Moreover, vertical jumping (countermovement jump test [CMJ]) and maximal sprints over 10, 20, 30, 40, 60, and 80 m were also assessed. In respect to 1RM in traditional squat, (a) no significant correlation was found with CMJ performance; (b) positive strong relationships (p < 0.01) were obtained with all the power measures obtained during both ballistic and traditional squat exercises (r = 0.53-0.90); (c) negative significant correlations (r = −0.49 to −0.59, p < 0.05) were found with sprint times in all the sprint distances measured when squat strength was expressed as a relative value; however, in the absolute mode, no significant relationships were observed with 10- and 20-m sprint times. No significant relationship was found between 10-m sprint time and relative or absolute power outputs using either ballistic or traditional squat exercises. Sprint time at 20 m was only related to ballistic and traditional squat performance when power values were expressed in relative terms. Moderate significant correlations (r = −0.39 to −0.56, p < 0.05) were observed between sprint times at 30 and 40 m and the absolute/relative power measures attained in both ballistic and traditional squat exercises. Sprint times at 60 and 80 m were mainly related to ballistic squat power outputs. Although correlations can only give insights into associations and not into cause and effect, from this investigation, it can be seen that traditional squat strength has little in common with CMJ performance and that relative 1RM and power outputs for both squat exercises are statistically correlated to most sprint distances underlying the importance of strength and power to sprinting.

Effect of Strength and High-Intensity Training on Jumping, Sprinting, and Intermittent Endurance Performance in Prepubertal Soccer Players

Abstract Ferrete, C, Requena, B, Suarez-Arrones, L, and Sáez de Villarreal, E. Effect of strength and high-intensity training on jumping, sprinting, and intermittent endurance performance in prepubertal soccer players. J Strength Cond Res 28(2): 413–422, 2014—The purpose of this study was to examine the effects of a 26-week on-field combined strength and high-intensity training on the physical performance capacity among prepubertal soccer players who were undertaking a competitive phase of training. Twenty-four prepubertal soccer players between the age of 8 and 9 years were randomly assigned to 2 groups: a control (C; n = 13) and an experimental group (S; n = 11). Both groups performed an identical soccer-training program, whereas the S group also performed combined strength and high-intensity training before the soccer-specific training. The 15-m sprint time (seconds), countermovement jump (CMJ) displacement, Yo-Yo intermittent endurance test (Yo-Yo IE), and Sit and Reach flexibility were each measured before (baseline) and after 9 (T2), 18 (T3), and 26 weeks (posttest) of training. There were no significant differences between the groups in any of the variables tested at baseline. After 26 weeks, significant improvements were found in the CMJ (6.72%; effect size [ES] = 0.37), Yo-Yo IE (49.57%, ES = 1.39), and Flexibility (7.26%; ES = 0.37) variables for the S group. Conversely, significant decreases were noted for the CMJ (−10.82%; ES = 0.61) and flexibility (−13.09%; ES = 0.94) variables in the C group. A significant negative correlation was found between 15-m sprint time and CMJ (r = −0.77) and Yo-Yo IE (r = −0.77) in the S group. Specific combined strength and high-intensity training in prepubertal soccer players for 26 weeks produced a positive effect on performance qualities highly specific to soccer. Therefore, we propose modifications to current training methodology for prepubertal soccer players to include strength and high-intensity training for athlete preparation in this sport.