According to a preprint study posted on medRxiv, wearing a cloth face mask did not result in any significant respiratory or cardiovascular changes during exercise, including heart rate, blood pressure, lactate, or oxygen saturation, irrespective of exercise intensity.

In a crossover study conducted at an intrahospital exercise physiology laboratory in São Paulo, Brazil, from April through November 2021, 35 individuals were analyzed. Of these, 31 were categorized as active and 4 as inactive. Wearing a mask had no effect on end-expiratory lung volume (EELV) and EELV/forced vital capacity ratio, heart rate, lactate, blood pressure, or oxygen saturation, regardless of gender. Wearing a mask was associated with a reduction in inspiratory capacity, respiratory frequency at peak but not at baseline, tidal volume except at baseline, ventilatory equivalent for carbon dioxide, time to exhaustion, forced vital capacity at rest, forced expiratory volume in 1 second at rest, and peak expiratory flow at rest, regardless of gender… (Medscape)