Introduction
The planning and scheduling of sports training involve setting certain goals and targets for the acquisition of peak performance (i.e., the optimal development of each physical quality specific to a given sporting activity) (21).
A number of studies have addressed the design of training schedules intended to improve performance. Lyle (20) reported on the improvement of sporting performance through a program of preparation and competition. Decisions on training criteria require a thorough analysis of the sport in question and careful selection and organization of the training exercises implemented.
The physiologic characteristics of soccer players and their response to the game suggest that a combination of metabolic demands takes place during play (23). Kinematic monitoring and analysis of actions, movements, and intensity should provide the starting point for any analysis of the demands of the sport in question (25). Although purposeful actions (e.g., acceleration, jumping, and kicking) require anaerobic exertion from the soccer player, most activity in the course of a match is of low or submaximal intensity (6,24). In the 90 minutes of the match, the most frequent activities require moderate- or low-speed running and thus demand aerobic metabolism (7).
Soccer is an intermittent, noncyclical sport, involving exertion of varying intensity and highly variable recovery times (24). Moreover, as Bangsbo et al. (6) have suggested, training should be aimed at improving the ability to undertake exercise at different speeds for long periods to develop what the authors term endurance capacity, or the capacity for repeated execution of high-intensity exercises.
Once the demands of the game have been determined, the nature of the training exercises must be addressed. Because these exercises have a direct or an indirect effect on the athlete's motor skills, they provide a major means of improving sporting performance (9). Available exercises are as numerous as they are varied. The most widely used training exercises can be classified in terms of their structure, their function, and the load involved (8). Even so, with the limited training time available, care must be taken when selecting exercises not only on the basis of structure, function, and load but also on the basis of their relevance to the sport in question.
Exercises are also generally graded by degree of difficulty or complexity. Training schedules tend to start with simple exercises that become progressively more complex and increasingly reflect the characteristics of the sport in question, because only specially loaded training can achieve the adaptations required (26).
The hypothesis shows that these special and specific exercises produced higher results of aerobic resistance and specific strength, with higher results in strength as a result of the greater number of sessions.
The aim of this study was to chart improvements in strength and endurance in professional soccer players in 1 season by using a selection of training exercises classified as general, special, and specific or competition-related exercises as part of a 1-year schedule.
Methods
Experimental Approach to the Problem
Improvements in aerobic endurance and strength were measured in terms of jumping capacity in 1 season (i.e., 4 macrocycles). Strength and aerobic endurance training schedules were divided into blocks. During the second half of the season (i.e., the last 2 macrocycles), strength training intensity was increased. Three types of exercise (i.e., general, special, and specific) were used to improve strength and aerobic endurance. By the end of each macrocycle, special and specific exercises predominated; general exercises prevailed during the rest of the macrocycle.
Subjects
Fifteen soccer players from the Third Division of the Football League from Spain took part in this study. Mean subject characteristics were 28.23 ± 3.37 years in age, 178.61 ± 3.85 cm in height, and 78.79 ± 5.99 kg in mass. Players sustaining injuries during the assessment period were excluded from the study.
Study Design
An annual training program was designed to comprise 4 macrocycles, in each of which preparation periods were followed by competition periods (Figure 1). The first 2 macrocycles consisted of 12 weeks each and were divided into 3 stages (development 1, development 2, and stabilization); the first 6 weeks contained more aerobic endurance training sessions (E1), and the last 6 weeks contained more strength training sessions (S1) (Table 1).
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Table 1: Distribution and orientation of training exercises and number of sessions devoted to strength and endurance training in the first and second macrocycles.
Figure 1: Annual training and competition program. Distribution of macrocycles and strength and endurance assessments.
The last 2 macrocycles also consisted of 12 weeks each (3 weeks of development 1, 4 weeks of development 2, and 5 weeks of stabilization). The first 4 weeks were largely devoted to aerobic endurance training (E2), and the remaining 8 weeks were devoted to strength training (S2) (Table 2).
Table 2: Distribution and orientation of training exercises and number of sessions devoted to strength and endurance training in the third and fourth macrocycles.
Training Program
To develop strength and aerobic resistance, 4 exercises were implemented (Table 3). Exercise 1 (e1) used maximum hold (strength) and a variable trajectory (endurance). Exercise 2 (e2) used fast loads (strength) and medium extensive intervals (endurance). Exercise 3 (e3) used horizontal jumps (strength) and medium intensive intervals (endurance). Exercise 4 (e4) used vertical jumps (strength) and short intensive intervals (endurance). During the stages of developer 1 and developer 2, the exercises of general and special characteristics (i.e., e1, e2, and e3) predominated. For the stabilization phase, the elements used resulted in an output of a more competitive aspect (i.e., e4) (Tables 1 and 2).
Table 3: Training program per session.
Pretesting and Post-testing Measurements
Aerobic endurance was measured with a step test (22) at the start of training, during the first preparation period, at the start of the second preparation period, and at the end of the season (Figure 1).
Explosive strength was studied with a set of jumps developed by Bosco (13): squat jumps (SJs), which are an assessment of lower-limb explosive strength; countermovement jumps (CMJs), which are an assessment of explosive strength with reuse of elastic energy; and CMJs with arm swing (CMJas), which are an assessment of explosive strength with reuse of elastic energy and coordination of movement.
All subjects were assessed on 4 occasions at the end of each macrocycle (Figure 1) by using an AGFR Technology infrared platform built into the MuscleLab system (model PFMA 30/0e, Bosco System, Neuromuscular Analysis Laboratory), installed at the training site. Three measurements were taken for each test. In each case, the best result was selected, and the other two were discarded (13).
Before aerobic endurance testing and jump testing, the subjects underwent warm-up exercises under the supervision of their physical trainer. These exercises were general (e.g., running, joint movement, and muscle tone-up) and specific to the test involved.
Reproducibility of the Variables
Tests were repeated on 2 different days in the week before training. The intraclass correlation values (interday) were as follows: SJ, 0.97; CMJ, 0.94; and CMJas, 0.99.
Statistical Analyses
Means and SDs were calculated by using traditional statistical techniques. Normality was tested with the Shapiro-Wilks test. A repeated-measures analysis of variance was used to compare mean values, and the Bonferroni adjustment was used for multiple comparisons. The significance level was set at P ≤ 0.05. The SPSS statistical package (version 11.0; SPSS, Inc., Chicago, Ill.) was used.
Results
Results of tests to assess strength (Table 4) and aerobic endurance (Table 5) showed changes in mean values between assessments.
Table 4: Mean results for squat jump, countermovement jump, and countermovement jump with arm swing tests.
Table 5: Mean results for Probst test.
Strength
Squat Jumps
Squat jump values were significantly greater in the second, third, and fourth assessments than in the first (Figure 2). A progressive, albeit not statistically significant, increase was noted in SJ values for assessments 3 and 4 compared to assessment 2.
Figure 2: Differences in mean squat jump values between assessments. *P < 0.05. **P < 0.01.
Countermovement Jumps
Values for assessments 3 and 4 were significantly greater than for assessment 1. Again, there was a progressive but not statistically significant increase in assessments 3 and 4 with respect to assessment 2 (Figure 3).
Figure 3: Differences in mean countermovement jump values between assessments. *P < 0.05. **P < 0.01.
Countermovement Jumps With Arm Swing
As in the other tests, the greatest values were recorded in assessment 4, with differences being statistically significant compared to assessments 1 and 2 but not compared to assessment 3 (Figure 4).
Figure 4: Differences in mean countermovement jump with arm swing values between assessments. *P < 0.05. **P < 0.01.
Aerobic Endurance
Test results (Table 5) showed a considerable improvement in assessments 2 and 3 (i.e., competition period) compared to assessment 1 (i.e., training period), with regard to the distance run and the maximal running speed. Differences were highly significant (P < 0.01). No differences were recorded between the 2 competition assessments (i.e., assessments 2 and 3).
Discussion
The main finding of this study was an increase in strength achieved through competition-specific training exercises. A trend has been reported in soccer toward more explosive strength movements and a faster game, requiring a greater intensity of physical actions and the ability to repeat these actions as many times as possible (7,12).
The results obtained in this study suggest that the more intensive the training geared toward a specific physical quality, the greater the benefits are. Similar findings have been reported by other authors, who observed an increase in specific strength, as measured only by jumping capacity, after a block of training focusing wholly on that specific quality (2,4,19).
Dudley et al (15) found that concurrent aerobic endurance training and strength training may negatively affect the latter. Gorostiaga et al. (16) reported not only that simultaneous aerobic endurance and strength training may have a negative outcome, but also that low-intensity running characteristic of plays during ball possession has a negative effect on strength, while not improving aerobic endurance. Therefore, it is suggested that training blocks should be scheduled for each physical quality.
Although there is a need to train aerobic resistance, there is also a need to work exclusively on building strength. Therefore, a session of high-intensity aerobic endurance can be added per week (17) with intensive exercises, which will not surpass 60 seconds of effort.
With regard to methodology, these results suggest that training comprising general, special, and sport-specific exercises, arranged consecutively, prompts a considerable increase in specific strength. In sports such as soccer, training should be geared toward improving explosive strength; thus, exercises involving considerable strength combined with great speed are likely to be the most effective (28).
High levels of strength are achieved by using high loading levels, such as isometric or dynamic activation through exercises of a general nature (18). In the current study, this type of exercise was performed at the start of training, in the development 1 stage. By contrast, the special or competition-specific exercises performed during the development 2 and stabilization stages approach, from the biomechanical and neuromuscular standpoints, competition conditions (i.e., increased speed and contraction) (3,4).
Adams et al. (1) reported that general, special, and specific exercises prompt an improvement in explosive strength. Wilson et al. (30) and Baker (2) found differences in efficiency among the 3 types of strength training. Comparing a general exercise (e.g., squat), a special exercise (e.g., jump squats with maximal power load), and a specific exercise (e.g., plyometric), they found that special exercises led to a greater increase in explosive strength in elite athletes. General exercises most increased strength in untrained subjects, largely because of learning processes rather than any increase in maximal strength.
Although some studies suggest that the greatest increases in strength are achieved through special exercises, the results obtained in this study indicate that a combination of exercise types prompts a greater increase in strength.
General and special exercises led to an increase in muscle contraction capacity. Specific exercises may improve the efficiency of the muscle stretch-shortening cycle and transfer effects through increased contractility and stretch reflex or muscle elastic properties (10). Patterns of motor unit recruitment and synchronization and stimulus frequency should be kept in mind when designing exercises enabling transfer to competition-specific movements (14). In this respect, Bobbert and van Soest (11) suggested that an individual increase in strength may delay jumping capacity, if the ability to control new levels of strength has not been worked on by using specific training exercises.
In the current study, the duration of the strength and aerobic endurance blocks varied from the first half to the second half of the season. Greater emphasis on strength training in the last 2 macrocycles (i.e., an increase in training from 6 to 8 weeks) led to significant changes in jumping capacity (Table 1). Willoughby (29) and Baker et al. (3) suggested that this may be the result of variations in training volume and intensity. Other authors, including Luebbers et al. (19), reported that 4- to 7-week blocks with 3 weeks of recovery after training constitute an ideal training schedule for increasing strength and jumping capacity.
Therefore, it is suggested that the stimulus frequency or number of training sessions should be increased in the early macrocycles to achieve a greater increase in strength. Stimulus magnitude and frequency are equally important in the last 2 macrocycles to avoid training-induced stagnation or adaptation, as reported by Siff and Verchoshaski (27).
To summarize, physical training in soccer should focus on strength training in 6- to 8-week blocks, and macrocycles should be longer during the second half of the season. Exercises should be largely general during the development 1 stage and largely special and specific during the development 2 and stabilization stages.
Practical Applications
The increase of strength and aerobic endurance in soccer must occur in separate blocks or specific cycles of strength or aerobic endurance. Within the macrocycles, aerobic endurance training must be preceded by strength training. In the second lap of the championship (i.e., the last 2 macrocycles), not only should the aerobic training be performed before the strength training, but it is also necessary to increment the training (i.e., the number of sessions) for strength in an inverse relationship to the work of aerobic endurance.
For the development of strength and aerobic endurance, general, special, and specific exercises must be implemented and organized in such a way that during the mesocycles of accumulation 1 and accumulation 2, these exercises are applied, and in the stabilization mesocycles, special exercises are performed.
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