Characterizing changes in fitness of basketball players within and between seasons

We assessed the magnitude of changes in fitness and anthropometric test scores of well-trained basketball players between phases of a year and over several years. Players were 1011 females and 1087 males in Basketball Australia’s State and National junior programs (1862 and 236 players respectively). Players undertook a set of three fitness and three anthropometric tests on 2.6 ± 2.0 (mean ±SD) occasions over 0.8 ± 1.0 y. Mixed modeling was used to estimate mean changes within and between seasons, and to estimate individual variability as the standard deviation of change scores between assessments. Changes were expressed as standardized (Cohen) effect sizes for interpretation of magnitudes (trivial <0.2; small 0.2-0.6, moderate 0.6-1.2). In the first 2 y National and State males showed small longitudinal improvements in body mass, skinfolds, and shuttle-run performance (effect size 0.28 – 0.42). After 2 y National females made small improvements in most tests (0.27 – 0.42), but National males showed a small decline in shuttle-run performance (0.55). Other changes in mean test scores within and between seasons were trivial. Individuals showed small to moderate variability about the mean change between phases (0.23 – 0.87) and between years (0.26 – 1.03), with State-level players having greater variation in all tests (State/National ratio 1.1 – 2.4). Coaches or sport scientists monitoring or modifying fitness of basketball players should recognize there is generally little overall change in mean fitness within and between seasons. They should also take into account the small to moderate changes in individuals.