Quantifying Long-Term Adaptations in Performance Variables in Adolescent Athletes: A 1.5 Year Longitudinal Training...

We examined the effects of resistance training over 1.5 years (two seasons). Body mass, strength, power, and aerobic capacity were assessed during the first 1.5 years of a standardised, progressive, blocked linear periodisation training program in adolescent males with no prior history of resistance training (N = 11, 16.4 ± 0.5 years). Testing occurred during the start of pre-season (SPS), end of pre-season (EPS), and end of season (EOS) during the first and second year of resistance training. Changes over time were assessed with within-group ANOVAs and follow-up independent t-tests. Differences in relative change that occurred during the first and second year of training for each variable were assessed with dependent t-tests. Body mass changed over time (p < 0.001, n²p = 0.794). Body mass increased from SPS to EPS (p = 0.008, Large) and EPS to EOS (p = 0.019, Large) in year 1, and from EOS in year 1 to SPS in year 2 (p < 0.001, Large). Bench press (p < 0.001, n²p = 0.806), squat (p < 0.001, n²p = 0.670), and medicine ball throw (p < 0.001, n²p = 0.350) changed over time. Bench press (Year 1: p < 0.001, Large; Year 2: p < 0.001, Large), squat (Year 1: p < 0.001, Large; Year 2: p < 0.001, Large), and medicine ball throw (Year 1: p = 0.007, Large; Year 2: p = 0.026, Large) increased from SPS to EPS in year 1 and year 2. Bench press (p = 0.010, Large) and squat (p = 0.004, Large) increased more from SPS to EPS during year 1 than year 2. By quantifying diminished returns, our study offers practitioners novel information, helping practitioners manage expectations, avoid excessive training and support long-term adolescent development.