Mixed
Variable-intensity (VI) cycling, when matched for average power output to steady-state (SS) cycling, results in significantly greater plasma glucose oxidation and reduced muscle glycogen utilization, yet yields equivalent subsequent time-trial performance.
If you are a trained cyclist, switching from steady-state to variable-intensity training (matching the same average power) will change how your body uses fuel (more blood glucose, less muscle glycogen). However, this metabolic shift does not translate to faster race times or time-trial performance. You do not need to use variable intensity solely to 'save glycogen' if your goal is faster performance at a specific average power; steady-state may be equally effective and potentially simpler to execute.
VI resulted in a 49% reduction in total muscle glycogen utilization vs. 65% for SS, while total Gluox was higher (99.2 6 5.3 vs. 83.9 6 5.2 g/140 min; P , 0.05)... Despite these metabolic differences, subsequent TT performance was similar (29.14 6 0.9 vs. 30.5 6 0.9 min for SS vs. VI).
Why this rating
Randomized crossover design with trained subjects, invasive metabolic measurements (biopsies, tracers), and performance outcomes.
Source
Metabolic and performance responses to constant-load vs. variable-intensity exercise in trained cyclists
G. S. Palmer et al. · Journal of Applied Physiology · 1999
DOI 10.1152/jappl.1999.87.3.1186
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