Fig. 3From: Beta-Adrenergic Receptor Blockade Effects on Cardio-Pulmonary Exercise Testing in Healthy Young Adults: A Randomized, Placebo-Controlled TrialCalculated chronotropic index (CI) in healthy subjects under placebo, 2.5 mg bisoprolol or 5.0 mg of bisoprolol. Mean values are represented by large horizontal bars and standard deviation by vertical bars in each condition. 7 subjects out of 21 (33%) under 5.0 mg of bisoprolol are included in the chronotropic incompetence zone (grey zone) situated below a chronotropic index of 0.6Back to article page