Wearing a cloth face mask while exercising leads to worse performance, according to the results of a small trial. It found that when donning a face covering, a person's exercise duration drops by 14 per cent while participants also recorded increased feelings of breathlessness and claustrophobia when exercising at higher intensities. The results of the trial on 31 healthy adults have been published online in the British Journal of Sports Medicine (BJSM). Thirty of the participants said that the task — running on a treadmill to exhaustion — was harder when wearing a face covering. World Health Organization (WHO) guidance backs up the finding, stating: 'People should NOT wear masks when exercising, as masks may reduce the ability to breathe comfortably'.