No Additional Effects of Block- Compared to Even-Periodization of Low-Intensity Training in Junior Cross-Country...

To compare effects of block periodization against evenly distributed low-intensity training on endurance performance in well-trained junior cross-country (XC) skiers.

Twenty junior cross-country skiers participated in a crossover design study. Athletes were matched by maximal oxygen uptake (VO2max) and sex and were randomly assigned to either BLOCK or EVEN interventions, each lasting 4 weeks, separated by a 1-week break. BLOCK performed 1 week at 160% of baseline endurance volume, followed by weeks of reduced volume, while EVEN maintained consistent volume. Total training volume was identical between conditions. Pretesting and posttesting measured VO2max, maximal aerobic speed (Vmax), and submaximal performance indices. Subjective markers of stress and recovery were also assessed daily.

No significant treatment-time interaction effects were found between the BLOCK and EVEN interventions for any performance variable, including VO2max (P = .83, d = -0.1), Vmax (P = .15, d = -0.4), or submaximal speed at 3 mmol⋅L-1 blood lactate concentration (V3mmol/L) (P = .55, d = 0.2). While both groups demonstrated significant within-group improvements in some performance variables, these gains were not statistically different between the 2 periodization strategies. The BLOCK group, however, reported significantly lower mood and perceived recovery during the high-volume week and the subsequent recovery week.

Block periodization of low-intensity training is not more effective for improving endurance performance in junior cross-country skiers than volume-matched, evenly distributed training. The concentrated, high-volume week of low-intensity training was well-tolerated and safe but failed to provide an additional performance stimulus. The findings indicate that for training with a lower physiological stress profile, consistent application, rather than concentration, is the primary driver of adaptation.