Refuting the myth of non-response to exercise training: 'non-responders' do respond to higher dose of training.
Level 2 - randomized trial
Individual randomized dose-response trial with within-subject escalation
PubMed 28133739 · doi:10.1113/JP273480
What was done
Seventy-eight healthy adults were divided into five groups performing one, two, three, four, or five 60-minute endurance exercise sessions per week (60 to 300 min/week) for 6 weeks. Non-response was defined as a change in maximal incremental exercise power output (Wmax) within the typical measurement error (±3.96%). Participants classified as non-responders completed a second consecutive 6-week training period with two additional 60-minute sessions per week. VO2max, hematology, and muscle biopsies were assessed before and after each 6-week intervention.
What was found
After the initial 6 weeks, Wmax significantly increased (P < 0.05) in groups 2, 3, 4, and 5, but not group 1. Non-responder rates were 69% in group 1 (60 min/wk), 40% in group 2 (120 min/wk), 29% in group 3 (180 min/wk), and 0% in groups 4 (240 min/wk) and 5 (300 min/wk). After the second 6-week period with increased volume, non-response was 0% across all individuals. Change in VO2max independently determined Wmax response (partial r >= 0.74, P < 0.001), with total hemoglobin mass being the strongest independent determinant of VO2max change (partial r = 0.49, P < 0.001).
Why it matters
This study demonstrates that cardiorespiratory non-response to standard exercise is dose-dependent rather than an inherent physiological inability to adapt. Increasing exercise volume effectively induced fitness gains across all previously non-responsive individuals.
Limits
The study was conducted exclusively in healthy adults, so findings may not generalize to clinical or elderly populations. Subgroup sample sizes were relatively small (approximately 15-16 participants per group), and long-term adherence or sustainability of high exercise volumes was not assessed.
Cited by
- context Approximately 40% of people do not show significant cardiorespiratory fitness improvement from standard moderate-intensity cardiovascular exercise alone (non-responders).