Physiological responses to high intensity interval training versus continuous moderate-intensity training in master athletes

High intensity interval training (HIT) can serve as an effective alternate to continuous moderate intensity training (CON), inducing similar or even superior physiological and performance changes in both healthy individuals and diseased populations. To our knowledge the effects of HIT have not been investigated in masters athletes. Methods: Twenty male athletes (47.2 \ub1 7.4 yr) were tested before (PRE) and after (POST) 8 weeks of HIT or CON. On different occasions, the participants carried out, on a motorised treadmill at 1% grade: a) an incremental exercise test up to voluntary exhaustion; b) moderate and high intensity constant load (CLE) running exercises. Breath by breath pulmonary O2 uptake (V\u2019O2) and heart rate (HR) were measured; vastus lateralis oxygenation indices (delta[deoxy(Hb+Mb)]), obtained by near infrared spectroscopy (NIRS), were considered as estimates of skeletal muscle fractional O2 extraction. Blood lactate concentration (La) was measured at rest and into recovery. To assess performance, a 5km time trial was carried out on an outdoor track. Results: In both CON and HIT: 1) The 5km performance significantly improved, despite the training volume was ~25% lower than their usual weekly volume. 2) V\u2019O2peak, GET and delta[deoxy(Hb+Mb)]peak, did not change. 3) Speed at GET was significantly higher in POST vs PRE. 4) During moderate intensity CLE, V\u2019O2, HR and La were significantly lower in POST vs PRE. During high intensity CLE, V\u2019O2, HR and La were significantly lower in POST vs PRE in HIT but not in CON. Conclusions: These results support a considerable role for HIT as a potent and time efficient training method also for masters athlete