The intraocular pressure response to lower-body and upper-body isometric exercises is affected by the breathing pattern.

We assessed the mediating role of the breathing pattern adopted during isometric exercise on the intraocular pressure (IOP) response in the back squat and biceps curl exercises. Twenty physically active young adults performed sets of 1-minute isometric effort against a load corresponding to 80% of the maximum load while adopting three different breathing patterns: (i) Constant breathing: 10 cycles consisting of 3 s of inhalation and 3 s of exhalation, (ii) 10-sec Valsalva: 3 cycles consisting of 10 s holding the breath and 10 s of normal breathing, and (iii) 25-sec Valsalva: 2 cycles consisting of 25 s of the Valsalva maneuver and 5 s of normal breathing. A rebound tonometer was used to semi-continuously assesses IOP during the six sets of 1-minute isometric effort (2 exercises × 3 breathing patterns). We found a progressive IOP rise during isometric effort (P < 0.001, ηp2 = 0.83), with these increases being greater when the breath was held longer (P < 0.001, ηp2 = 0.58; 25-sec Valsalva > 10-sec Valsalva = constant breathing). There was a trend towards higher IOP values for the back squat in comparison to the biceps curl, although these differences did not reach statistical significance for any breathing pattern (corrected P-value ≥ 0.146, d ≤ 0.69). These findings reveal that glaucoma patients or those at risk should avoid activities in which the breath is held, especially when combined with physical exercise modalities that also promote an increment in IOP values (e.g. isometric contractions).