Short-Term Performance Effects of Three Different Low-Volume Strength-Training Programmes in College Male Soccer Players
João Brito,1,2 Fabrício Vasconcellos,2,3 José Oliveira,4 Peter Krustrup,5,6 and António Rebelo2
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Abstract
This study aimed to analyse the short-term performance effects of three in-season low-volume strength-training programmes in college male soccer players. Fifty-seven male college soccer players (age: 20.3±1.6 years) were randomly assigned to a resistance-training group (n=12), plyometric training group (n=12), complex training group (n=12), or a control group (n=21). In the mid-season, players underwent a 9-week strength-training programme, with two 20 min training sessions per week. Short-term effects on strength, sprint, agility, and vertical jump abilities were measured. All training groups increased 1-RM squat (range, 17.2–24.2%), plantar flexion (29.1–39.6%), and knee extension (0.5–22.2%) strength compared with the control group (p<0.05). The resistance-training group increased concentric peak torque of the knee extensor muscles by 9.9–13.7%, and changes were greater compared with the control group (p<0.05). The complex training group presented major increments (11.7%) in eccentric peak torque of the knee flexor muscles on the non-dominant limb compared with the control group and plyometric training group (p<0.05). All training groups improved 20-m sprint performance by 4.6–6.2% (p<0.001) compared with the control group. No differences were observed in 5-m sprint and agility performances (p>0.05). Overall, the results suggest that in-season low-volume strength training is adequate for developing strength and speed in soccer players.
Keywords: soccer, resistance training, plyometric training, complex and contrast training
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Introduction
During a typical soccer game, players perform 150–250 brief intense actions (Bangsbo et al., 2006), including changes in activity every 3–5 s, 30–40 sprints, 30–40 tackles and jumps (Mohr et al., 2003), decelerations, kicks, and dribbles. Soccer is becoming increasingly more athletic; hence, the contribution of strength, power, and their derivatives (acceleration, sprinting, and jumping) might be beneficial in many game situations (Hoff and Helgerud, 2004). Therefore, conditioning coaches feel the need to include ancillary strength-training sessions as part of routine football training programmes.
Traditional modalities to improve strength, include resistance training and plyometric exercises with movement patterns as close as possible to specific football skills, aiming to warrant the highest degree of transference between strength gains and soccer technical skills. For this purpose, conditioning coaches often refer to the complex training method, which combines weight lifting of heavy-loads with plyometric exercises, set for set, in the same workout (Robbins, 2005). The rational underlying this method is the theory of a post-activation potentiation of the neuromuscular system, i.e. a phenomenon induced by a voluntary conditioning contraction, typically performed at maximal or near-maximal intensities, that may increase peak force and the rate of force development during subsequent twitch contractions (Tillin and Bishop, 2009).
In soccer, many studies have shown that strength training combining weight lifting and plyometric exercises results in significant improvements in match-related physical abilities (Kotzamanidis et al., 2005; Maio Alves et al., 2010; Perez-Gomez et al., 2008). Notwithstanding, soccer is a team sport, so that the largest proportion of training practice is devoted to field-based conditioning drills to ensure the players preparedness for specific demands of the match play. This is a major issue during the competitive period, when players might have little time for ancillary strength training. Conditioning coaches might thereby feel the need to rationalise the time and volume devoted to strength-training programmes, as a strategy to guarantee that players accomplish with the prescribed training regimens.
In the present study, the short-term effects of three different in-season low-volume strength-training programmes on strength, sprint, agility, and vertical jump performance of soccer players were tested. It was examined whether adding plyometric-skill exercises to a programme with high-load weight training could be advantageous, compared to basic resistance training or plyometric training only.
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Material and Methods
Participants
Fifty-seven adult male soccer players were invited to participate in the study. The participants were college students engaged in different local soccer clubs. All players were informed about the protocol, and signed an informed consent form before the investigation. The Scientific Board from the Faculty of Sport, University of Porto approved the design of the study. The players were then randomly assigned to 4 groups: resistance-training group (RT, n=12), plyometric-training group (PT, n=12), complex-training group (CT, n=12), and control group (CG; n=21). The groups were similar (p>0.05) in age (CG: 20.7±1.0 yrs; RT: 20.3±0.9 yrs; PT: 20.0±0.6 yrs; CT: 19.9±0.5 yrs), body mass (CG: 71.4±2.1 kg; RT: 72.8±1.8 kg; PT: 71.6±2.3 kg; CT: 72.2±1.1 kg), and body height (CG: 178±5 cm; RT: 176±5 cm; PT: 176±5 cm; CT: 180±7 cm). Furthermore, during pre-training, no statistical differences between the groups were observed with regard to any of the tests performed.
Measures
All participants accomplished a 3-day testing set; the players were evaluated within 1 week, in different days interspersed by at least 48h. Primarily, the players were evaluated in one repetition maximum (1-RM) in the squat, knee extension, and plantar flexion exercises, aiming to determine maximal strength and to further prescribe the training workload. On the following day, the players were evaluated for isokinetic strength. The last day of testing was devoted to measure the squat jump (SJ) and countermovement jump (CMJ), 5- and 20-m sprinting, and agility performance. The first evaluation was carried out before the start of the intervention programme, and the second after 9 weeks of training.
The determination of 1-RM was conducted according to the procedures suggested by Kraemer and Fry (1995). The evaluations were carried out after a 1-week familiarisation period, in which participants learned the exercise execution techniques. The participants were always kept under surveillance of one member of the research team.
Isokinetic assessment (Biodex, System IV, USA) included bilateral measurements of knee extensors (quadriceps, Q) and flexors (hamstrings, H). Measurements were preceded by a 5-min warm-up on a cycle ergometer and a specific sub-maximal protocol on the dynamometer in order to familiarize the participants with the isokinetic device and test procedure. Participants were tested in the seated position with the back inclined at 85º using stabilisation straps at the trunk, abdomen and thigh to prevent inadequate joint movements. The arms were held comfortably across the chest. The axis of the dynamometer lever arm was aligned with the distal point of the lateral femoral condyle. A range of knee motion of 90º (0º=full extension) was provided both for the concentric and the eccentric tests and the gravity correction procedure was employed. The testing protocol consisted of concentric actions of both quadriceps (Q) and hamstrings (H) at 60º/s (3 repetitions). Afterwards, the hamstring muscles were tested in the eccentric mode at 60º/s (3 repetitions). Testing sets were separated by a 1-min rest interval. During the test, oral and visual feedback was given. The concentric H:Q peak torque ratio (conventional H/Q ratio) and the eccentric hamstrings:concentric quadriceps peak torque ratio (functional H/Q ratio) were calculated.
In the SJ, participants performed a maximal vertical jump with hands on the waist, starting from an angle of 90° at the knee; in the CMJ, the participants performed a maximal vertical jump starting from a standing position, with arm swing not allowed. All jumps were performed on a jump mat (Digitime 1000, Digitest, Finland). Participants performed 2 trials in each jump type, and the best result was used in further analysis.
Sprint and agility performance were evaluated outdoors, in an artificial turf ground, using photoelectric cells (Speed Trap II, Brower Timing Systems, USA). Sprint evaluation was accomplished through a flat sprint test that was carried out in a straight 20-m line. The times were measured through 3 pairs of photoelectric cells positioned at the starting line, at 5 and 20 m. The lower (fastest) time of 2 trials for each test was retained for analysis. Agility was evaluated by the T-test, as described by Semenick (1990). The subject began with both feet 30 cm behind the starting line (A). The player sprinted forward 10 m to point B and touched a marker (cone) with the right hand, then sprinted 5 m to the left and touched another marker (C) with the left hand, then sprinted 10 m to the right and touched a third marker (D) with the right hand, and finally sprinted back to point B and touched the marker with the left hand, after which he turned 90º, and returned to the starting point A running passed the finishing line. The photoelectric cells were placed at the starting/finishing line (A) to record the elapsed time. Players were instructed to run as fast as possible. The fastest time of two trials was retained for analysis.
Procedures
The 9-week in-season strength training intervention programme was conducted in 3 experimental groups with two training sessions per week. Additionally, all groups performed their routine soccer training, based on technical and tactical drills, and small-sided games. The training programmes were adapted from Maio Alves et al. (2010). After a 10-min warm-up wit
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