Refuting the myth of non‐response to exercise training: ‘non‐responders’ do respond to higher dose of training

Abstract

Key pointsr The prevalence of cardiorespiratory fitness (CRF) non-response gradually declines in healthy individuals exercising 60, 120, 180, 240 or 300 min per week for 6 weeks.r Following a successive identical 6-week training period but comprising 120 min of additional exercise per week, CRF non-response is universally abolished.r The magnitude of CRF improvement is primarily attributed to changes in haemoglobin mass. r The potential for CRF improvement may be present and unveiled with appropriate exercise training stimuli in healthy individuals without exception.Abstract One in five adults following physical activity guidelines are reported to not demonstrate any improvement in cardiorespiratory fitness (CRF). Herein, we sought to establish whether CRF non-response to exercise training is dose-dependent, using a between-and within-subject study design. Seventy-eight healthy adults were divided into five groups (1-5) respectively comprising one, two, three, four and five 60 min exercise sessions per week but otherwise following an identical 6-week endurance training (ET) programme. Non-response was defined as any change in CRF, determined by maximal incremental exercise power output (W max ), within the typical error of measurement (±3.96%). Participants classified as non-responders after the ET intervention completed a successive 6-week ET period including two additional exercise sessions per week. Maximal oxygen consumption (V O 2 max ), haematology and muscle biopsies were assessed prior to and after each ET period. After the first ET period, W max increased (P < 0.05) in groups 2, 3, 4 and 5, but not 1. In groups 1, 2, 3, 4 and 5, 69%, 40%, 29%, 0% and 0% of individuals, respectively, were non-responders. After the second ET period, non-response was eliminated in all individuals. The change inV O 2 max with exercise training independently determined W max response (partial correlation coefficient, r partial ࣙ 0.74, P < 0.001). In turn, total haemoglobin mass was the strongest independent determinant ofV O 2 max (r partial = 0.49, P < 0.001). In conclusion, individual CRF non-response to exercise training is abolished by increasing the dose of exercise and primarily a function of haematological adaptations in oxygen-carrying capacity.

Exercise training response heterogeneity: physiological and molecular insights

“…Other reports have demonstrated a doseresponse relationship between exercise and reductions in blood pressure [36] and inflammation [37] in these same postmenopausal women, with the highest dose being the most effective (up to 200 min/week, which is 50 min longer than the dose currently recommended in the USA for producing substantial health benefits according to physical activity guidelines [38]). In agreement, a recent report determined that response to a dose eliminates non-response in V O 2peak of healthy individuals [7]. Such a high volume of exercise training, however, may not be feasible or practical for all individuals.…”

“…In one report, the investigators found that V O 2peak non-response was abolished after increasing the exercise dose in healthy individuals [7]. While these data are strong in terms of V O 2peak as the response variable, other important response variables known to be improved by exercise training were not assessed (e.g.…”

CrossTalk opposing view: Exercise training volume is more important than training intensity to promote increases in mitochondrial content

“…). In the only study to investigate the effect of different volumes of training on Mito VD , increasing training volume (by increasing days of weekly training from 1 to 4) led to greater increases in Mito VD (there was no further increase when training volume was increased further by training 5 days per week) (Montero & Lundby, ). In the only study to directly compare the effects of different training intensities, Mito VD increased by 47% following SIT and 88% following MICT (although this difference between groups was not significant; Shepherd et al .…”

Exercise and trainability: contexts and consequences

“…In this issue of The Journal of Physiology , Montero and Lundby () subjected a large number of healthy young men ( n = 78) to an intense programme of endurance training. The subjects were divided into five groups and trained one, two, three, four or five days per week for 6 weeks.…”