Mixed
At moderate-to-high aerobic exercise intensities (65-90% VO2max), glycogenolysis is regulated by posttransformational factors (free Pi and AMP) rather than the transformation of glycogen phosphorylase, which remains in excess of flux requirements.
To burn more glycogen during cardio, you must increase your power output (intensity), not just hope your enzymes are 'activated.' At moderate intensities, your body uses post-transformational signals (like AMP and Pi levels) to fine-tune exactly how much glycogen to break down, keeping the enzyme ready but not necessarily running at max capacity.
The results of this study indicate that glycogen phosphorylase transformation is independent of increasing power outputs, despite increasing glycogenolytic flux, suggesting that flux through glycogen phosphorylase is matched to the demand for energy by posttransformational factors, such as free Pi and AMP.
Why this rating
Controlled human trial with direct muscle biopsies and metabolite analysis.
Source
Regulation of skeletal muscle glycogen phosphorylase and PDH at varying exercise power outputs
Richard A. Howlett et al. · American Journal of Physiology-Regulatory, Integrative and Comparative Physiology · 1998
DOI 10.1152/ajpregu.1998.275.2.r418
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