Block periodization vs. traditional periodization in high-intensity functional training: a randomized crossover study

Background High-intensity functional training (HIFT) requires the combined development of strength and metabolic conditioning. This study examined whether concentrating high-intensity training loads into specific blocks provides advantages over a traditional evenly distributed approach in experienced athletes. Methods Twenty experienced HIFT athletes (34.5 ± 9.8 yrs, 80.9 ± 13.7 kg, 1.77 ± 0.11 m, training experience: 5.8 ± 3.2 yrs) completed two six-week, load-matched intervention phases (block periodization (BP) versus traditional periodization (TP)) in a randomized controlled crossover design. Both conditions included five weekly sessions, but differed in the temporal distribution of high-intensity training (HIT) and low-intensity training (LIT) sessions, with BP concentrating HIT sessions into specific loading weeks and TP distributing intensity more evenly across the intervention. Outcome measures included maximal strength, benchmark workouts, physiological stress assessed via countermovement jump (CMJ), and health-related parameters including resting blood pressure, blood glucose concentration, and body composition. Results BP was associated with greater improvements in maximal strength compared to TP. Specifically, significant group differences favoring BP were observed for the isometric mid-thigh pull (p = 0.038, d = 0.82), deadlift one repetition maximum (p = 0.018, d = 0.85), and CrossFit ® Total (p = 0.027, d = 0.78). Furthermore, BP resulted in a significant reduction in waist circumference (p = 0.019, d = -0.79), suggesting a favorable anthropometric change. Monitoring data revealed a significant acute reduction in CMJ during the concentrated loading week of BP (p 0.001, d = -1.41), consistent with a state of functional overreaching. No significant between-condition differences were observed for metabolic conditioning, resting blood pressure and blood glucose concentration. Conclusion Concentrated loading through block periodization was associated with favorable changes in selected maximal strength outcomes in trained HIFT athletes without compromising metabolic conditioning or cardiovascular health markers. This approach effectively induces functional overreaching and represents a viable strategy to optimize performance adaptations in HIFT.