Soccer is one of the most popular sports in the world (1,22). During the 1998 Federation International de Football Association (FIFA) World Cup, an estimated 40 billion spectators watched the game on television (19). The game is 90 minutes in duration with a break at the midway point (halftime). During the contest there is no stoppage in play as the teams transition from offense to defense. Each team has 11 players (1 goalie and a combination of 2-4 midfielders, 1-3 forwards, and 2-4 defenders) on the field at all times. Players are required to play both offense and defense with limited substitution patterns. Soccer is a complex sport, and an individual's success as a team member depends on a number of variables such as aerobic and anaerobic physical fitness, speed, body composition, style of play, team tactics, and psychological factors (22). From a skill perspective, soccer could be described as a sport that demands fine balance and control of the ball utilizing short sprints, turning, kicking, and tackling (25).
In recent years, several studies have examined the characteristics of elite soccer players (1,2,5-7,17,18). These studies have demonstrated that elite players possess high levels of both aerobic and anaerobic capabilities and technical and cognitive skills, which allow them to excel in their sport. Other soccer-oriented studies have examined performance-related seasonal changes in professional and Division I National Collegiate Athletic Association (NCAA) soccer teams (9,11-13,20,21). The aim of these investigations was to examine whether in-season training and competition deteriorates, improves, or maintains physical performance. The results of these studies have indicated that the magnitude of change, if there is any at all, depends on the level of play and preseason conditioning (9,11-13,20,21). Ideally, these results could serve as an important tool in the development of guidelines optimizing off-season and in-season training programs.
Similar to NCAA Division I soccer teams, NCAA Division III soccer teams generally participate in a periodized strength and conditioning program. However, many NCAA Division III athletic programs do not have a full-time strength and conditioning coach, or if a coach does exist, he or she is required to work with all teams. As a result, the ability to provide daily supervision to the conditioning program of Division III athletes may be difficult. In addition, differences between NCAA Division I and III institutions in respect to athletic-related financial aid, coach/athlete contact times, and athletic department budgets (15) may contribute to differences in optimal preparation of athletes for competition. Therefore, the primary purpose of this study was to measure seasonal changes in various aerobic- and anaerobic-related physical performance tests in male NCAA Division III soccer players. A secondary purpose was to provide a normative data for various aerobic- and anaerobic-related physical performance tests for this population.
Experimental Approach to the Problem
Prior to the beginning of the study, each participant completed an orientation session in the laboratory to familiarize himself with the protocol and the equipment that will be used in the study. Maximal aerobic capacity test (O2max); 10-, 30-, and 40-m sprints, the pro-agility test, and the Wingate anaerobic power test (WAnT) were performed prior to the start of the regular season (PRS trial; mid August) and 12 weeks later following the last game of the season (POS trial; mid November). The objectives of this approach were to (a) examine whether there were seasonal changes in various aerobic- and anaerobic-related physical performance tests, and (b) provide normative data for various aerobic- and anaerobic-related physical performance tests for this population.
Twelve apparently healthy starters were recruited from the active members of the men's soccer team to participate in the study (Table 1). In the past 5 years the soccer team has consistently been ranked in the top 20 among male NCAA Division III programs. Prior to commencing the study, all participants received a detailed explanation of both the benefits and the risks involved with the study. Each participant completed a medical history form and gave their written informed consent. All experimental procedures were conducted in the Exercise Science Laboratory and the gymnasium at North Carolina Wesleyan College (NCWC) and were approved by the NCWC Institutional Review Board for Human Participants Experimentation. Participants were instructed to abstain from caffeine and exercise for at least 24 hours prior to testing. In addition, participants were required to record a 3-day dietary recall prior to both testing periods.
All procedures were conducted in the Exercise Physiology Laboratory and the gymnasium at NCWC. Environmental conditions during testing were approximately 21°C and 45% relative humidity. On day 1, body composition was measured and the participants completed a test session on a treadmill (Trackmaster; Newton, Kansas, USA) for determination of maximal oxygen consumption O2max; on day 2, the participants completed a battery of tests that examined anaerobic physical performance.
Height was measured to the nearest 0.1 cm using a stadiometer, and body mass was measured to the nearest 20 g (Ohaus Champ II Model CH 150 R11, Ohaus Corporation, Florhan Park, New Jersey, USA). Percent body fat was estimated from a 7-sites skinfold measurement using Harpenden skinfold calipers (British Indicator Ltd, Luton, United Kingdom) and calculated using recommended formulas (24).
The O2max test was performed on a motor-driven treadmill and consisted of 3 minutes of continuous, progressive graded exercise stages (Bruce Protocol) until volitional exhaustion (16). The 0% and the 5% stages were omitted from the protocol in consideration of the athletic population. Using this test, expired respiratory gases were collected and analyzed for oxygen and carbon dioxide concentration at 30-second intervals (mini CPX by Vacumed; Ventura, California, USA). O2max was defined as the averaged O2 in the last 30 seconds of the exercise.
Speed was assessed at 10-, 30-, and 40-m increments using tape from 1 corner of the basketball gym to the other. Each subject performed 3 attempts at all 3 distances (for a total of 9 sprints) and the fastest time was recorded for each distance. Time was measured by a digital timing device that had a built-in voice and weight sensor that started recording as the facilitator spoke the word “go” into its microphone, and time ceased when the sprinter stepped on the mat at the end of their run (Probotics Inc; Huntsville, Alabama, USA). Test-retest reliabilities for these measures from our laboratory have been shown to be r >0.90.
To assess agility and quickness subjects performed the pro-agility test (5-10-5 test). Each subject straddled the middle/marked line and sprinted in 1 direction for 5 yards. The subject changed direction and sprinted back 10 yards to another line and pivoted back and sprinted through the starting line (5 yards). The mat was positioned at the middle line, which is the starting and finishing point of the exercise (Probotics Inc). Each subject performed 3 attempts and the fastest time was recorded.
Wingate Anaerobic Power Test (3)
Participants were allowed to warm up on the bike (which was connected to a computer) until they instructed for the test to begin (Monark 834E; Lidingo, Sweden). Once the test had been initiated, they were instructed to pedal as fast as possible and 7.5% of their bodyweight was then dropped on the front wheel as resistance. Participants continued to pedal using maximal force for 30 seconds after the resistance had been dropped. Using the Monark computer software, peak and average anaerobic power values were recorded. During all exercise bouts, subjects were encouraged by teammates and testing instructors to carry out the test to their maximum ability.
PRS and POS descriptive statistics are presented in the form of means and standard deviation (Table 1). Individual dependent t-tests were used to evaluate differences between PRS and POS (Table 2). Statistical significance was set at p ≤ 0.05, and all data were reported as mean ± SD.
The PRS and POS anthropometric data were not significantly different (Table 1). Performance measures are presented in Table 2. From PRS to POS, O2max was significantly increased (p ≤ 0.05) and the 10- and 30-m sprints were significantly lower (p ≤ 0.05). The 40-m sprint, pro-agility test, and WAnT results were not significantly different between PRS and POS.
Although a number of studies have investigated performance-related seasonal changes in professional and male NCAA Division I soccer players, to our knowledge this is the first study to examine changes in various aerobic- and anaerobic-related physical performance tests during a competitive season in male NCAA Division III soccer players.
Body mass and percent body fat were similar to previously reported studies (4,7,11,20). Similar to other investigations, our study demonstrated that body mass (4,7,11,12) and percent body fat (11) are maintained throughout the competitive season, but the results contrast with others (4,7,11,20). Silvestre and colleagues (20) reported that body mass in Division I male soccer players increased during a competitive season, and Miller et al. (12) indicated that percent body fat was elevated in female Division I soccer players. Others have reported decreases in percent body fat during the competitive soccer season (4,7). These differences may be explained by differences in preseason level of fitness, training regimen, and playing position.
In contrast to other studies that displayed a reduction or no change in maximal oxygen consumption (7,9,12,20,21), the present study demonstrated a significant increase in O2max by ∼7% following the competitive season (Table 2). When comparing the PRS O2max value (51.05 ± 5.97 ml·kg−1·min−1) to normative values for O2max, the value is considered as “above average” (24). However, this value is well below the reported average of elite professional and collegiate (NCAA Division I) soccer players, which ranges between 55 and 65 ml·kg−1·min−1 (9,20-22). Vanfraechem and Thomas (23) have argued that, for a player to be comparative and to play a pivotal role in a top-level soccer match, 65 ml·kg−1·min−1 should be the minimal O2max value. The POS O2max value (54.64 ± 4.90 ml·kg−1·min−1) is still relatively low and, at best, it represents the low end of the average value of elite professional and collegiate soccer players. It was previously demonstrated that any gains in aerobic ability over the playing season are associated with improvement in lactic and ventilatory thresholds rather than an increase in O2max values, which is not the case in our investigation (Table 2). Edwards et al. (7) have shown that following the playing season lactic and ventilatory threshold increased significantly (81 vs. 86% and 80 vs. 85% O2max, respectively), whereas there was no change in O2max. In addition, it was also demonstrated that following the playing season the anaerobic threshold occurred at a higher velocity and heart rate, indicating a positive influence of the playing season on aerobic performance (4). Furthermore, a recent study has reported that highly conditioned soccer players may experience a reduction in performance at the conclusion of the playing season, which may be attributed to an acute overtraining syndrome (9). Therefore, it is possible that the participants in this study started the season with less than optimal levels of aerobic capacity and improved their level of fitness throughout the season. It is important to note that individual data demonstrated that some of the participants in study showed better than the average O2max during the PRS and the POS (Figure 1).
The present study has demonstrated that 10- and 30-m sprints significantly improved during the playing season (Table 2). This finding is in contrast to a recent study that reported no change in sprint times in a NCAA Division I men soccer team over the playing season. Similar to the changes in aerobic fitness in the present study, these findings may also demonstrate a lower level of fitness in this study at the beginning of the season. This is supported by previous work that has suggested that speed improvements during the competitive season may be more of a function of a low level of fitness at the beginning of the season (4). In addition, Kraemer et al. (9) have demonstrated that even when athletes are well conditioned at the beginning of the season, sprint times may increase as a result of training and competition demands. Similar to the O2max data, individual data showed variation in the 10- and the 30-m sprints (Figures 2 and 3).
Although other anaerobic physical performance tests did not show any significant difference from PRS to POS (Table 2), it is essential to mention that the values for WAnT (6,10) and the pro-agility test (8) were lower than other comparable studies. More important, although the pro-agility test was not significantly different from PRS to POS (p < 0.1), there was a clear improvement from PRS to POS. This finding is pivotal because most physical performance-related tests (excluding WAnT) in the present study have demonstrated an improvement in performance as the season progressed. As previously mentioned, this finding may indicate a less than optimal level of fitness at the beginning of the season. Studies that showed no change or perhaps a decrease in performance were performed on Division I programs (4,9). In contrast, this study was conducted using Division III athletes. These athletes may not have a strength and conditioning staff that works with the team on a yearly basis. Thus, the ability to maximize performance at the start of the season may be compromised in programs that do not have the luxury of strength and conditioning coaches.
The results of this study suggest that NCAA Division III male soccer players appear to improve aerobic and anaerobic performance measures during the competitive soccer season. This appears to contrast with previous studies examining NCAA Division I soccer athletes. Potentially, there are many factors that may lead to these differences, although, in our view, the 2 most important factors are the fundamental distinction between NCAA Division I and Division III athletics and the lack of dedicated strength and conditioning personnel to assist in the development of optimal off-season conditioning programs.
By definition, Division III schools do not offer athletic scholarships, compete in athletics as nonrevenue-generating institutions, and may not redshirt a freshmen (15). Thus, the structure in this NCAA Division does not offer the same incentives (financial and other) as NCAA Division I (14,15). Consequently, it is possible that some of the players may choose not to train or follow the official training regimen because of a lack of financial leverage by the coaching staff. Alternatively, it is possible that because of limited resources that NCAA Division III schools provide to their athletic department, the strength and conditioning coach may be overwhelmed and hence cannot provide an optimal year-round periodization program.
No matter what the cause is, this study also suggests that if soccer players report to preseason training camp in inferior condition, the ability to improve physical performance is much greater. The bigger issue is how the team will fare during the early stages of the season when they are at a competitive disadvantage. One way to partially remedy this problem is to engage in an ongoing process of recruiting better-quality players that may closely follow an off-season training regimen and, therefore, be better prepared at the beginning of the playing season.
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Keywords:© 2009 National Strength and Conditioning Association
soccer; aerobic capacity; physical performance; seasonal changes