A treadmill control protocol combining nonlinear, equally smooth increases in speed and gradient: Exercise testing for subjects with gait and exercise limitations

Abstract

Incremental exercise testing with a linear increase in work rate is the recommended method for clinical exercise testing. A recent protocol (A), incorporating a linear increase in speed and a nonlinear increase in gradient, has been developed which addresses some limitations of traditional testing methods. It does not account for those with an impaired gait pattern. We propose and assess a novel protocol (B) incorporating nonlinear increases in both speed and gradient. We theoretically develop a new treadmill control protocol (B), determine oxygen uptake response linearity, initial metabolic rate and cardiopulmonary response parameters (peak oxygen uptake, lactate threshold, dynamic O 2 cost) and compare the outcome measures with two previously verified IET protocols (A and C (constant speed with linear increase in gradient)). Feasibility and outcomes were explored with a subject with incomplete spinal cord injury. The average initial metabolic rate ( V ˙ O 2 ) was substantially lower during protocol A (0.49 ( ± 0.12 ) l min −1) and protocol B (0.52 ( ± 0.05 ) l min −1) than during protocol C (1.35 ( ± 0.04 ) l min −1). The average linearity of the V ˙ O 2 response during protocols A and B (correlation co-efficients 0.97 ( ± 0.00 ) and 0.95 ( ± 0.02 ), and co-efficients of determination 0.94 ( ± 0.01 ) and 0.91 ( ± 0.02 ), respectively) were higher than during protocol C (correlation co-efficient 0.91 ( ± 0.02 ) and co-efficient of determination 0.84 ( ± 0.02 )). The average dynamic O 2 cost for protocol C (6.53 ( ± 0.46 ) ml min −1 W −1) was lower than that of protocol A (10.02 ( ± 1.16 ) ml min −1 W −1) and protocol B (10.03 ( ± 0.91 ) ml min −1 W −1). No differences were found in these parameters between protocols A and B. The new protocol B performs better than protocol C and is comparable with protocol A. When testing subjects with an impaired gait pattern, it may be advantageous to use the new protocol B due to the gradual increases in both speed and gradient throughout the test.