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Performance Changes in NBA Basketball Players Vary in Starters vs. Nonstarters Over a Competitive Season

Gonzalez, Adam M.1; Hoffman, Jay R.1; Rogowski, Joseph P.2; Burgos, William2; Manalo, Edwin2; Weise, Keon2; Fragala, Maren S.1; Stout, Jeffrey R.1

Journal of Strength and Conditioning Research: March 2013 - Volume 27 - Issue 3 - p 611–615
doi: 10.1519/JSC.0b013e31825dd2d9
Original Research
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Gonzalez, AM, Hoffman, JR, Rogowski, JP, Burgos, W, Manalo, E, Weise, K, Fragala, MS, and Stout, JR. Performance changes in NBA basketball players vary in starters vs. nonstarters over a competitive season. J Strength Cond Res 27(3): 611–615, 2013—The purpose of this study was to compare starters (S) with nonstarters (NS), on their ability to maintain strength, power, and quickness during a competitive National Basketball Association (NBA) season. Twelve NBA players were assessed at the beginning and end of the competitive season. However, because of trades and injury, only 7 (S = 4, NS = 3) players (28.2 ± 3.4 years; 200.9 ± 9.4 cm; 104.7 ± 13.9 kg; 7.2 ± 1.9% body fat) participated in both testing sessions and underwent analysis. Anthropometric performance (repetitive vertical jump power [VJP], squat power [SQT power], and reaction time) and subjective feelings of energy, focus, alertness, and fatigue were recorded during each testing session. Results were interpreted using magnitude-based statistics to make inferences on true differences between starters and nonstarters using the unequal variances t-statistic. Starters played an average of 27.8 ± 6.9 minutes per game and nonstarters played an average of 11.3 ± 7.0 minutes per game. During the course of the season, changes in VJP indicated that starters were likely to increase VJP ([INCREMENT] = 77.3 ± 78.1 W) compared to nonstarters ([INCREMENT] = −160.0 ± 151.0 W). There also appeared to be a possible beneficial effect on maintaining reaction time in starters ([INCREMENT] = 0.005 ± 0.074 seconds) compared with nonstarters ([INCREMENT] = 0.047 ± 0.073 seconds). In addition, no clear differences in ΔSQT power were seen between starters ([INCREMENT] = 110.8 ± 141.4 W) and nonstarters ([INCREMENT] = 143.5 ± 24.7 W). Changes in subjective feelings of energy indicated that starters were very likely to maintain their energy over the course of a season. It also appeared possible that starters were able to have a more positive response to subjective measures of fatigue and alertness than nonstarters, with only trivial differences between starters and nonstarters in regards to maintaining focus. Results of this study suggest that NBA players may enhance lower-body power, repetitive jump ability, and reaction during a competitive season, which appear to be enhanced with the stimulus of playing time.

1Sport and Exercise Science, University of Central Florida, Orlando, Florida

2Orlando Magic Basketball Club, Orlando, Florida

Address correspondence to Dr. Jay R. Hoffman, jay.hoffman@ucf.edu.

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Introduction

A professional basketball season imposes a great amount of physiological stress on athletes. The typical competitive National Basketball Association (NBA) season consists of 82 regular season competitions over a span of 5.5 months (2–5 games per week). In addition, athletes also play a month of preseason games and practice and potentially up to 2 months of a postseason. On top of games, players are also required to participate in daily or twice-a-day practice sessions in preparation for competition. The training stress incurred over the long competitive NBA season may subject athletes to the risk of overtraining syndrome if appropriate adjustments are not made to training programs. Overtraining symptoms are often noticed when an athlete is unable to fully recover from the demands of a sport and often hinders the athlete's ability to maintain optimal performance (4,19,20). Assessing sport-specific performance characteristics of professional basketball players during the season may provide coaches and training staffs an ability to identify and make necessary adjustments to reduce the risk for overtraining.

There is limited research published pertaining to NBA athletes and their demanding season. However, there have been several studies examining the physiological changes during a season of competition in intercollegiate and European-level basketball players (2,8,16). Research has clearly indicated that basketball is predominantly an anaerobic sport (5,17), and several investigations on intercollegiate and European players have indicated that strength, power, agility, and speed can differentiate between different levels of competition or predict playing time (3,11,14). Several studies have indicated that performance measures can be maintained during a season of competition (9,10), whereas others have indicated that gains in strength can be achieved in previously untrained basketball players during a competitive season (8). However, none of these studies examined a season that was of similar length to that seen of an NBA team. Considering the length of the basketball season in the NBA, those athletes who are part of the regular rotation (starters) may experience a greater fatigue than those who are not playing consistently (nonstarters [NS]). Identification of players who experience decreases in performance may provide an opportunity for the coach to make appropriate adjustments to their training volume, training intensity, or even playing time to maximize potential as the season progresses toward the playoffs. Thus, the purpose of this study was to compare starters (S) with nonstarters, on the ability to maintain strength, power, and quickness during a competitive NBA season.

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Methods

Experimental Approach to the Problem

Professional basketball players on an NBA team performed strength, power, and agility assessments during a competitive basketball season. During each testing period, players also completed questionnaires regarding their subjective feelings of energy, focus, fatigue, and alertness. These measures were part of a program designed to assess the physiological stresses of a competitive NBA season. Testing began before the start of the regular season and concluded a week before the end of the regular season. Testing occurred every month, but only the first and last testing periods were analyzed. All players participated in a regular weekly resistance training program during the competitive season. The frequency of resistance training was dependent upon travel schedule, but players did lift between 8–12 times per month. To determine the effect of playing time on performance changes, starters were compared with nonstarters.

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Subjects

Twelve players under contract to play for the NBA franchise Orlando Magic were assessed at the beginning of the competitive season. However, because of trades and injury, only 7 players (28.2 ± 3.4 years; 200.9 ± 9.4 cm; 104.7 ± 13.9 kg; 7.2 ± 1.9% body fat) participated in end of season testing. All analyses were performed with those players that participated in both pre- and postseason testing. All performance assessments were part of the athlete's normal training routine. Players gave their informed consent as part of their requirements as a team member, which is consistent with the policies of the University's Institutional Review Board for use of human subjects in research.

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Performance Variables

All athletes performed anthropometric (height, body mass, and body composition), repetitive vertical jump power (VJP), squat power (SQT power), quickness, and reaction time. In addition, during each testing session, subjective feelings of energy, focus, alertness, and fatigue were recorded. The order of testing was consistent for all testing sessions. Upon reporting to the training facility, athletes dressed in their normal practice uniforms and underwent anthropometric assessments, completed the subjective questionnaires, and then performed the vertical jump test, reaction test and concluded with the squat test. Test-retest reliabilities for all assessments were R > 0.90. Total time played (total minutes), average minutes per game, games played, and games started were recorded from the team's official statistics.

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Anthropometric Measures

Anthropometric assessments included height, body mass, and percent body fat (%BF). Body mass was measured to the nearest 0.1 kg. Body composition was assessed via skinfold analyses. Percent body fat was estimated via a 6-site skinfold test. The sites measured were the triceps, scapula, chest, iliac crest, anterior thigh, and abdomen, using methodology previously described (13). Body density was calculated using the equation of Jackson and Pollock (13), and %BF was calculated using the equation of Siri (18). The same research assistant performed all skinfold assessments.

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Vertical Jump Power

Each player performed five consecutive countermovement jumps. During each jump, players stood with their hands on their waist at all times and were instructed to maximize the height of each jump while minimizing the contact time with the ground between jumps. Subjects wore a belt connected to a Tendo Power Output Unit (Tendo Sports Machines, Trencin, Slovak Republic). The velocity of each jump was calculated, and the mean power output (VJP) for each repetition was recorded and used for subsequent analysis.

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Reaction Time

Lower-body reaction time was measured with a 20-second reaction test on the Quick Board (The Quick Board; LLC, Memphis, TN, USA) reaction timer. Subjects stood on a board of 5 circles, in a 2 × 1 × 2 pattern. Subjects straddled the middle circle and reacted to a visual stimulus located on a display box that depicted 1 of 5 potential lights that corresponded with the circles on the board. Upon activation of the light, the subject attempted to move the foot closest to the circle that corresponded to the visual stimulus. Upon a successful connection, the next stimulus would appear. The total number of successful attempts for the 20-second test and the average time between the activation of the light and the response to the corresponding circle was recorded.

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Squat Power

Power output during the squat exercise was measured for each repetition with a Tendo Power Output Unit (Tendo Sports Machines,). The Tendo unit consists of a transducer attached to the end of the barbell, which measured linear displacement and time. Subsequently, bar velocity was calculated, and power was determined when barbell load was entered into the microcomputer. The mean power output (SQT power) was recorded for each repetition and used for subsequent analysis. Test-retest reliability for the Tendo unit in our laboratory has consistently shown R > 0.90. The squat test consisted of 2 sets of 5 repetitions at load approximating 80% of the athlete's 1 repetition maximum in the squat exercise.

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Subjective Measures of Energy, Focus, Alertness, and Fatigue

Subjects were instructed to assess their subjective feelings of energy, focus, fatigue, and alertness using a 15-cm visual analog scale (VAS). The scale was anchored by the words “low” and “high” to represent extreme ratings where the greater measured value represented the greater feeling. Questions were structured as “My level of energy is,” ”My level of focus is,” “My level of alertness is,” and “My level of fatigue is.” The VAS was assessed at each test date, and subjects were asked to rate their feelings at that time by marking on the corresponding line. The validity and reliability of VAS in assessing fatigue and energy has been previously established (15).

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Statistical Analyses

The effects of the NBA season were calculated as the change from pre- to postseason measurements among starters and nonstarters. Magnitude-based inferential analyses were used as an alternative to normal parametric statistics to account for the small sample size (n = 7). Several studies have supported magnitude-based inferences as a complementary statistical tool to null hypothesis testing for reducing interpretation errors (1,12). The precision of the magnitude inference was set at 90% confidence limits, using a p value derived from an unpaired t-test, and the threshold values remained constant at ±0.2 for the small sample size. Inferences on true differences between starters and nonstarters were determined using the unequal variances t-statistic on a published spreadsheet (1). Inferences were calculated on whether the true population effect was substantially positive, negative, or trivial based on the range of the confidence interval relative to the value for the smallest clinical worthwhile effect. If the likely range substantially overlaps both positive and negative values, it is inferred that the outcome is unclear. The chance that the effect was positive or negative was evaluated by the following scale: <1%, almost certainly not; 1–5%, very unlikely; 5–25%, unlikely; 25–75%, possible; 75–95%, likely; 95–99% very likely; and >99% almost certain (12). Results were interpreted using magnitude-based statistics and reported as mean ± SD.

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Results

Starters (n = 4) played an average of 1813 ± 639 total minutes (27.8 ± 6.9 minutes per game) and nonstarters (n = 3) played an average of 543 ± 375 total minutes (11.3 ± 7.0 minutes per game) over the competitive season. Evaluation of magnitude inferences indicated a very likely difference in playing time between starters and nonstarters. Magnitude-based inferences on changes in performance and anthropometric measures are depicted in Table 1. During the season, it appeared possible that starters maintained their body mass (0.5 ± 1.2 kg), whereas nonstarters lost their body mass (−0.9 ± 3.1 kg). Magnitude-based inferences on the Δchange in body composition indicated a possible beneficial effect of starters (0.025 ± 1.389%) on maintaining %BF compared with starters (0.833 ± 1.443%). The Δchanges in VJP indicated that starters were likely to increase VJP (77.3 ± 78.1 W) compared with nonstarters (−160.0 ± 151.0 W). Examining the individual responses of each player revealed that 3 of the 4 players who are starters increased VJP, whereas all 3 players who are nonstarters decreased VJP during the season (see Figure 1). Magnitude-based inferences indicated that a competitive NBA season had a possible beneficial effect on maintaining reaction time in starters (0.005 ± 0.074 seconds) compared with nonstarters (0.047 ± 0.073 seconds). In addition, there appeared to be no clear difference in ΔSQT power between starters (110.8 ± 141.4 W) and v (143.5 ± 24.7 W). Interestingly, all players (both starters and nonstarters) increased SQT power during the course of the basketball season.

Table 1

Table 1

Figure 1

Figure 1

Pre- to postseason changes in subjective measures of energy, fatigue, focus, and alertness can be observed in Figure 2. Magnitude-based inferences on these changes can be seen in Table 2. Changes in subjective feelings of energy indicated that the ability of starters to maintain their energy was very unlikely over the course of a season. It also appeared possible that starters were able to have a more positive response to subjective measures of fatigue and alertness than nonstarters. There appeared to be trivial differences between starters and nonstarters in regards to the ability to maintain focus.

Table 2

Table 2

Figure 2

Figure 2

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Discussion

The NBA season is a long arduous event that may pose a significant limitation to the athlete's ability to maintain performance levels. Although all players on the roster practice and travel, the athlete's who are part of the coaches regular playing rotation (get in the game on a consistent basis for extended period of time) may experience greater levels of fatigue and risk experiencing performance decrements if appropriate rest and recovery are not achieved (4,19). However, to our knowledge, this is the first study to attempt to quantify the magnitude of performance changes during an NBA basketball season. The results of this study indicated that starters were not only able to maintain their physical performance levels throughout the season but the greater playing time appeared to have provided a greater stimulus for enhancing VJP. In addition, starters appeared to maintain their body composition and reaction time better than nonstarters. Greater playing time also appeared to have positive effects on feelings of fatigue and alertness, whereas the only detriment associated with starters was a possible decrease in energy as the season progressed. The team was successful as reflected by a 52 to 30 regular season record and made the playoffs, but lost in the first round.

The measures used to assess performance changes in this study were consistent with what has been recommended for basketball players (5,9,17). Basketball is predominately an anaerobic sport (5,7,11,17), and studies have shown that lower-body strength and power performance are indicators of playing time in basketball players (11). As such, it appears imperative that strength and power measures should be maintained during a season. Interestingly, previous studies have demonstrated that this is attainable in National Collegiate Athletic Association Division I basketball players, as long as these players continue to lift through the season (8,10). Furthermore, strength gains can be achieved during the season, especially in novice or less experienced athletes (10). However, in contrast to the collegiate basketball season, the NBA season is nearly twice as long, possibly potentiating a greater cumulative fatigue in the NBA athlete. Despite this concern, the results of this study provide additional support for in-season strength and power improvements in NBA athletes. It appears that greater playing time acts as a stimulus for enhancing jump power performance. All players were required to perform a repetitive 5-jump test. This was intended to mimic the repetitive jumping experienced by players fighting for rebounds during a game. The greater jump power performance seen in starters compared with nonstarters suggests that the additional playing time, or the intensity of the jumps performed in an NBA game, provides a greater stimulus for eliciting improved repeated jump performance. This likely contributed to the greater reaction time observed in starters as well.

Other investigators examining European basketball athletes participating in longer competitive season than collegiate athletes, but less than NBA athletes, have reported that anabolic/catabolic balance is maintained during the season (16). This suggests that the physiological stress associated with that specific competitive scenario was well tolerated by those athletes. Although we did not measure hormonal changes, performance results of this study do suggest that the athletes were able to withstand the rigors of the NBA season. Still, fatigue can manifest itself in several different ways (4). Considering that energy levels were more affected in starters than nonstarters suggests that some negative results were seen toward the end of the season. Although speculative, we may have started to see the initial signs of an overtraining syndrome. Interestingly, fatigue appeared to manifest itself to a greater extent in nonstarters than starters. This may be related to dissatisfaction associated with insufficient playing time. A previous study has shown that the mood of professional basketball players, especially fatigue and tension, is influenced by personal factors related to the athlete's relationship to the coach or team administrators (6).

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Practical Applications

The importance of monitoring elite basketball players' performance for overtraining is crucial not only to the athletes but also the success of teams. However, it is important to acknowledge that each athlete responds individually to the stresses of practice and games. Although the results of the team may be consistent, it is important for the strength and conditioning coach to examine individual player performance as well. When needed, specific adjustments to the athlete's daily routine (i.e., greater recovery, less time on the court) may prevent potential performance decrements that may not manifest as part of the team results. Results of this study suggest that NBA players may enhance lower-body power, repetitive jump ability, and reaction during a competitive season. This appears to be enhanced with the stimulus of competition.

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Keywords:

sport; overtraining; strength; reaction time; power

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