As in the case of several court- and field-based team sports, basketball requires athletes to perform an intermittent high-intensity physical activity stressing the aerobic and the anaerobic system (16). Particularly, high aerobic fitness is an important feature to improve basketball performance (5,8,23), for example, enhancing the ability to recover from the anaerobic efforts during a game (26), to reiterate sprints or high-intensity accelerations with short recovery intervals (17,21), and to prepare players to sustain an appropriate training load volume (24). Consequently, the ability to assess the aerobic fitness in basketball players may play a significant role for both coaches and sport scientists engaged in basketball performance and physiological evaluation (22).
Over the years, as an alternative to the laboratory protocols that are time consuming and require trained staff and expensive equipment, several field tests have been proposed as practical alternatives for the assessment of aerobic fitness in basketball players (22). Particularly, the 20-m multistage shuttle run is widely used by basketball athletes as a field test for determining aerobic fitness(22), having a strong correlation with VO2max (r = 0.92–0.93) (19,20). However, the game demands and required fitness are not directly assessed by the aforementioned test (25) because in basketball, and in other team sports (e.g., soccer), the exercise is intermittent and players must repeatedly perform intense, short sprint exercise. Recently, the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) (2,13) has been assessed for validity in male young basketball players, showing that it may be considered a valid field test to assess aerobic fitness in basketball players (8). This is because it was designated to evaluate the athlete's ability to repeatedly complete short distance, high-intensity running efforts, eliciting maximal aerobic responses while significantly stressing the anaerobic energy system (13). These characteristics are typical of many ball game sports, such as basketball (2,8).
However, despite the wide use of this test (for a full review, see ), there is little information about the potential role of the Yo-Yo IR1 to discriminate the aerobic performance in young basketball players at different skill levels. Furthermore, no study focused the attention on the influence that age-related physical and physiological variables have on the Yo-Yo IR1 performance. Given the increasing attention on young athletes and the emphasis on identifying and developing young talent at an early age (the so-called talent identification and development) (27), an investigation into the differences in the Yo-Yo IR1 performance may lead to useful information to identify if the Yo-Yo IR1 may predispose certain players toward success in basketball. These results could be of practical value to coaches and strength and conditioning professionals for further development of talent selection and profiling procedures in basketball, as already shown in soccer (15).
Therefore, the aim of this study was to evaluate the Yo-Yo IR1 ability to determine intermittent endurance performance differences between elite and subelite young basketball players and a group of nonathletic healthy age-matched male athletes (age groups U-14 to U-17).
Experimental Approach to the Problem
This study is an observational study aimed to assess the ability of the Yo-Yo IR1 to distinguish the specific endurance performance between elite and subelite young basketball players and a group of nonathletic healthy age-matched male athletes (age groups U-14 to U-17). Thus, in a cross-sectional design, 119 male adolescents performed over a period of 5 weeks (once per week) 2 sessions of the Yo-Yo IR1 to get acquainted with the test procedures and, subsequently, 3 sessions to determine the reliability of the test. All the test procedures were standardized according to previous work (2,13). For the experimental conditions, the running surface, altitude, temperature, and humidity were controlled to reduce the potential influences of these variables. Because typical age-related differences were observed in the participants' height and body mass, these variables were considered in the analysis as potential confounders of the results. Thus, we included them as covariates. However, only the participants' body mass reached levels suggesting that potential influence on the Yo-Yo IR1 performance occurred. Consequently, only participants' body mass was taken into consideration to evaluate the Yo-Yo IR1 ability to determine specific endurance performance differences between young basketball players.
On 125 male adolescents recruited, only 119 performed the whole protocol. The 6 dropouts registered were attributable to injuries and illnesses checked during the 5-week period. Of the total 119 subjects, 46 were from an Italian national basketball team (elite players) (U-14, n = 15; U-15, n = 15; U-17, n = 16); 42 were from an Italian regional basketball team (subelite players) (U-14, n = 15; U-15, n = 14; U-17, n = 13); and 31 were healthy age-matched male athletes (nonathletic) (U-14, n = 12; U-15, n = 8; U-17, n = 11). All the players were members of the development program of the same national (elite players) and regional basketball club (subelite players), respectively. The nonathletic age-matched participants were from an Italian State School. Given that according to the basketball federation rules the players are matched and compete by chronological age rather than biological maturation, the players were pooled by age group, exactly the way they are matched in training and competition. The elite and subelite U-14 groups undertook 3- and two 1.5-hour training sessions per week, respectively, and played a 40-minute match on the weekend. The elite and subelite U-15 groups had 4 and 3 weekly training sessions of the same duration, respectively, and a 40-minute match. The elite and subelite U-17 trained 5 and 4 times per week with a duration of 1.5 hours, respectively, with a 40-minute match on the weekend. Moreover the nonathletic U-14, U-15, and U-17 groups were healthy male adolescents with no experience in sports and without any pathological disorder (e.g., diabetes, obesity). Physical characteristics of the participants are presented in Table 1. Written consent was obtained from the participants' parents or guardians after being thoroughly informed of the purpose and potential risks of the study. All the experimental procedures were approved by the University Human Research Ethics Committee, which followed the ethical principles laid out in the 2008 revision of the Declaration of Helsinki.
This study was performed over a period of 5 weeks during the last third of the competitive season (April to May 2011). All the participants undertook 2 familiarization trials of the Yo-Yo IR1 in the 2 weeks before testing (once per week). The test sessions were performed over 3 weeks (once per week) to determine the reliability of the Yo-Yo IR1. For the basketball players, the test sessions were carried out in an indoor basketball court at least 3 days after the last competition match, at the same time of the day (17:00–20:30 hours). Team training intensity and volume were reduced the day before testing. For the nonathletic group, the test sessions were carried out in the indoor court of the school, at the same time of the day (10:00–13:30 hours). For all the experimental conditions, the running surface was the same and consisted of wood-block floor. All the participants were instructed to consume their usual diet on the days before testing. No food was allowed 2–3 hours before testing. The altitude to which the courts were located ranged from 138 to 181 m. During the weeks, the temperature in the indoor courts ranged from 17.3 to 20.4° C and humidity from 60.5 to 78.6%.
The results are expressed as mean ± SD. Intraclass correlation coefficient (ICC) and SEM expressed as a coefficient of variation (CV) were used to determine the reliability of the Yo-Yo IR1 (29). The ICC and SEM as a CV for the Yo-Yo IR1 are shown in Table 2.
A 2-way analysis of variance (ANOVA) was used to evaluate between-performance levels differences in the anthropometric characteristics. The Bonferroni post hoc test was used to specify where significant differences lay. Mean height and body mass significantly different (p < 0.01) from elite, subelite, and nonathletic U-14 to U-17 counterparts (Table 1). Consequently, a 2-way analysis of covariance (ANCOVA) was used to compare the Yo-Yo IR1 performances for the 3 performance levels (elite, subelite, and nonathletic) across the 3 age groups (U-14, U-15, and U-17). The participants' height and body mass were considered as covariates. The purpose of including covariate is twofold: (a) to reduce within-group error variance and (b) the elimination of confounds. A preliminary analysis evaluating the homogeneity-of-regression assumption indicated that the relationship between the participants' height (i.e., covariate) and the Yo-Yo IR1 performances (i.e., dependent variable) differed significantly as a function of performance levels and age groups (i.e., independent variables) (p < 0.01). Thus, only body mass was controlled for because this is potential confounding factors in the analysis, influencing the dependent variable (i.e., the total distance covered). Follow-up univariate analyses were undertaken using ANOVA and post hoc Bonferroni-corrected pairwise comparisons tests where appropriate. To provide an estimate of the proportion of variance that may be attributed to the performance levels and age groups, the strength of association measure, referred to as Omega-Squared (ω2), was used (12). The magnitude of the changes was assessed using effect size (ES) statistic with 90% confidence intervals (3). The ES were classified according to Hopkins (http://www.sportsci.org. Accessed October 2011): <0.2 = trivial, 0.2–0.6 = small, 0.6–1.2 = moderate, 1.2–2.0 large, >2.0 = very large. The statistical analyses were performed using the software IBM SPSS Statistics (version 18.0.0, IBM Corporation, Somers, NY, USA). The level of significance was set at p < 0.01.
The Yo-Yo IR1 results according to the performance levels and the age groups are presented in Table 3. A preliminary analysis evaluating the homogeneity-of-regression assumption indicated that the relationship between the body mass (i.e., covariate) and the Yo-Yo IR1 performance (i.e., dependent variable) did not differ significantly as a function of performance levels and age groups (i.e., independent variable) (p = 0.864 and 0.783, respectively). The ANCOVA indicated that the interaction between performance level and age group was not significant (p = 0.184), although significant differences across performance levels and age groups were noted (p = 0.001). However, only 28.2% (ω2 = 0.282) and 6.1% (ω2 = 0.061) of the total variance in Yo-Yo IR1 performances was accounted for by the 3 performance levels and age groups, respectively, controlling for the effect of the participants' body mass. Follow-up tests were conducted to evaluate pairwise differences among the adjusted means for performance level and age groups. The Bonferroni procedure was used to control for type 1 error across the 6 pairwise comparisons (α' = 0.01/6 = 0.0017). The results showed that only elite athletes had significantly higher Yo-Yo IR1 performances compared with that of subelite athletes (1,271 ± 385 vs. 861 ± 428 m; p < 0.0017; ES = 1.0 ± 0.35, moderate) and the nonathletic group (1,271 ± 385 vs. 738 ± 345 m; p < 0.0017; ES = 1.45 ± 0.38, large), controlling for the effect of their body mass (Table 3).
To the best of our knowledge, this is the first study to thoroughly investigate the evolution of the ability to perform the Yo-Yo IR1 in male basketball adolescents. Typical between-performance levels and -age groups differences in the Yo-Yo IR1 were observed (Table 3), suggesting that Yo-Yo IR1 may distinguish the aerobic performance abilities between elite junior basketball players compared with their subelite counterparts and a nonathletic group. Despite this, when the effect of the participants' body mass was controlled, the Yo-Yo IR1 can only distinguish between the performance ability of elite basketball players in comparison to their subelite counterparts despite similar weekly training volumes (p < 0.0017; ES = 1.0 ± 0.35, moderate). Furthermore, a significant difference was also reported between elite basketball players and an age-matched nonathletic healthy control group (p < 0.0017; ES = 1.45 ± 0.38, large) (Table 3).
The evidence that the Yo-Yo IR1 discriminate aerobic performance between elite, subelite, and nonathletic groups is consistent with the findings of Drinkwater et al. (9), which showed male Australian junior national-level basketball players had higher aerobic performances than their state-level counterparts Furthermore, the results of this study are similar to those found by Veale et al. (28), which showed that the Yo-Yo IR1 test successfully distinguished the aerobic performance of an elite junior Australian football playing group compared with their subelite counterparts and a group of nonathletic healthy aged-matched participants.
According to Malina et al. (14), the differences in aerobic fitness in male fitters and no fitters seem to be not attributable to individual differences in maturity status. Despite the maturity status not being controlled in this study, the differences in the Yo-Yo IR1 performance observed in this study may be affected by factors that have been shown to be relevant in basketball players such as (a) the intensity and number of weekly training, (b) the performance efficiency, (c) the motivation during the test, and (d) training status (10,11,13,30). Furthermore, the evidence that the Yo-Yo IR1 seems to be not accurate to discriminate the performance levels of junior basketball players across different age groups is probably related to the body composition. This is because of body composition, as hemoglobin increases, and hormonal changes, which appear to improve markedly during the adolescent year, influencing the aerobic trainability in young boys (1,6,11,18). Consequently, body composition may interfere with the ability of the Yo-Yo IR1 to differentiate for age and the aerobic performance.
However, a limitation of this study was that participants were grouped by chronological age. Thus, the biological maturity of the players was not taken into account. Also, muscle mass differences among players were not determined, because muscle mass, more than whole-body mass, appears to be potentially useful in providing an enhanced functional capacity in aerobic fitness (1). Therefore, assessing the Yo-Yo IR1 performance in junior basketball players according to maturity status and lean body mass may be the basis for future research.
This study describes the cross-sectional evolution of the Yo-Yo IR1 performance ability in elite, subelite junior basketball players, matched with a group of nonathletic healthy young male athletes across 3 age groups (U-14 to U-17). This study demonstrates that the Yo-Yo test is accurate only to discriminate elite junior basketball players, but it cannot be used to differentiate the specific aerobic performance for age. In light of this finding, basketball coaches and strength and conditioning professionals should consider in their basketball-specific testing batteries Yo-Yo IR1 as the aerobic specific test to assess and to check players' preparedness for elite level (4), together with strength and explosive-power ability performance assessment (7). This is because (a) the endurance performance represents a very important fitness component in the selection and profiling of young basketball players and (b) the Yo-Yo IR1 test proved to be a valid, reliable, and easily available measurement tool of a player's basketball-specific endurance capacity.
We are grateful to the participants involved in this study. Furthermore, we thank Professors Giuseppe La Torre and Marco Corradini for their valuable technical support.
No grant support was provided for this study. The results of this study do not constitute endorsement of the product by the authors of the National Strength and Conditioning Association.
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