Gymnastik- och idrottshögskolan, GIH

Purpose Usage of beta-blockers may influence heart rate response during exercise testing. The study aimed to investigate the impact of Propranolol, a non-selective beta-blocker, on the predictive validity of a commonly used submaximal cycle test, the Ekblom-Bak test (EB-test), for the estimation of maximal oxygen uptake (VO2 max).

Methods The study was a double-blinded crossover study including 28 participants (14 women), aged 21-59 years. VO2 max was estimated by the EB-test and measured during a maximal incremental exercise test during placebo and 10 mg Propranolol beta-blockade condition. The EB-test estimates VO2 max based on the difference in heart rate, Delta HR, between two work rates (4 min cycling on each), a factor corresponding to the higher rate, heart rate at the lower rate, and age.

Results Maximal heart rate (mean +/- SD; 165.5 +/- 16.5 vs. 181.4 +/- 9.8 bpm), Delta HR (36.4 +/- 13.2 vs. 43.0 +/- 11.4 bpm), and measured VO2 max (48.2 +/- 6.2 vs. 50.4 +/- 7.0 ml/kg/min, 3.55 +/- 0.74 vs. 3.67 +/- 0.71 L/min) were significantly lower in the beta-blockade condition compared to placebo (P = < .001). This led to an overestimation of VO2 max by the EB-test during beta-blockade, + 0.377 L/min (95% CI 0.281-0.473 L/min, + 11.2%), with no overestimation seen in the placebo condition, + 0.030 L/min (95% CI (- 0.112)-0.172 L/min + 0.8%). The coefficient of variance, indicating variance of estimated VO2 max on an individual level, was lower during beta-block condition, 6.6%, compared to placebo, 9.9%.

Conclusion The EB-test systematically overestimated VO2 max compared to measured VO2 max during beta-blockade condition. Future research is needed to refine the test equation for usage in populations using beta-blockers.