Gross Efficiency Response to Endurance Training
Phenotypic trade-off with VO₂max adaptation
Participants
n=43 trained cyclists in total: 14 in Experiment 1 (season-long observation) and 29 in Experiment 2 (12-week two-group training study; arithmetic on the abstract's group sizes)
Protocol
Key Findings
Experiment 1 followed 14 trained cyclists across five phases of a self-coached season with an incremental laboratory test; Experiment 2 trained 29 cyclists for 12 weeks in two randomly allocated groups (Group A prescribed specific high-intensity sessions in the first six weeks, Group B restricted in intensive work; both allowed high-intensity work in the second six weeks).
Both experiments showed training-related increases in GE but not in VO₂max, and an inverse within-subject correlation between GE and VO₂max (r = −0.32, P<0.05 across the season; r = −0.78, P<0.01 for the changes over the first six weeks in Group A). The phenotype table below is an interpretation of that correlation, not a classification the paper reports:
| Phenotype | Pattern |
|---|---|
| VO₂max responder | Higher gain in VO₂max, smaller GE gain |
| Efficiency responder | Smaller VO₂max gain, larger GE improvement |
| Dual responder (rare) | Both improve significantly |
| Non-responder | Neither improves significantly |
Implications
Different athletes adapt through different physiological pathways (inference from the within-subject correlation)
"Aerobic improvement" can come from either ceiling expansion (VO₂max) OR efficiency improvement (more power per O₂)
Cycling efficiency is itself trainable — both experiments showed training-related GE increases; the size of typical GE changes over training cycles is not given in the abstract
Phenotype classification should include GE, not just VO₂max