Dallam et al. 2018, nasal versus oral breathing in recreational runners

Study of 10 recreational runners who had already trained with nasally restricted breathing for more than six months, tested with no control group of oral breathers. Nasal-only breathing produced no difference in VO₂max, time to exhaustion or peak lactate compared with oral breathing, so it did not raise maximal capacity. At 85% of maximal steady-state intensity, nasal breathing lowered ventilation and the ventilatory equivalents (the litres of air breathed per litre of oxygen used and per litre of carbon dioxide produced) and slightly lowered oxygen uptake, indicating better ventilatory economy for the same work. Because the participants were already adapted to nasal breathing, the results cannot be generalised to a runner switching without preparation, and no performance or race outcome was measured. A tiny, uncontrolled study; it offers no evidence that nasal breathing makes a runner faster.