Acute leucocyte, muscle damage, and stress marker responses to high-intensity functional training

High-intensity functional training (HIFT) has become more popular, and the number of practitioners has increased; however, it remains unclear whether perturbations in the immune parameters occur, even after one single bout. Our aim was to examine acute leucocyte, muscle damage, and stress marker responses following a single 'Cindy' workout session, and compare the results between novice and experienced participants.

Twenty-three HIFT practitioners (age 31.0 ± 1.0 years) completed the 'Cindy' workout. They were categorized as novice (3-8 months of experience; n = 10) and experienced (≥18 months; n = 13). White blood cell (WBC) count, plasma creatine kinase (CK) activity, blood cortisol level, and lactate concentration were measured. Blood analysis was performed before (pre-ex), immediately after (post-ex), 30 min after (post-30 min), and 24 h after (post-24 h) a single 'Cindy' workout session.

WBC count was higher post-ex (6.8 to 11.8x103/μL) and returned to baseline values within post-30 min (p<0.01). Neutrophil (3.3 to 4.5x103/μL) and lymphocyte levels (2.8 to 5.9x103/μL) were higher post-ex and returned to baseline values after post-24 h, yet lymphocytopoenia (2.2x103/μL) was observed at post-30 min (p<0.01). CK increased post-ex (174.9 to 226.7 U.L-1) and remained elevated post-24 h. Cortisol (14.7 to 17.0 μg/dL) and lactate (1.9 to 13.5 mmol.l-1) responses increased post-ex, but only the lactate level was reduced at post-30 min (p<0.01). The experienced participants had higher WBC, lymphocyte, and cortisol concentrations post-ex than the novice ones (p<0.01).

A single HIFT session elicited significant acute perturbations in WBC count, stress markers, and muscle tissue, which is like other similar regimens. Importantly, the experienced participants showed greater lymphocyte and cortisol responses than the novice ones.