Mixed
PGC-1α is a central regulator of exercise-induced mitochondrial biogenesis, but it is not strictly obligatory as biogenesis can still occur in its absence due to biological redundancy.
While PGC-1α is a key protein involved in building mitochondria, you don't need to worry about 'activating' it specifically. It is naturally upregulated by the stress of exercise. The fact that your body has redundant pathways means that as long as you challenge your muscles with endurance or high-intensity exercise, your body will find a way to build mitochondria, even if one specific pathway is less active.
The notion that PGC-1a is essential for endurance training adaptation, however, has been challenged by findings that contraction-induced mitochondrial biogenesis is still observed in PGC-1a knockout mice... This biological redundancy indicates that perhaps the only obligatory response to exercise is the defense of homeostasis itself.
Why this rating
Based on knockout mouse studies and human molecular analyses.
Source
Molecular Basis of Exercise-Induced Skeletal Muscle Mitochondrial Biogenesis: Historical Advances, Current Knowledge, and Future Challenges
Christopher G. R. Perry et al. · Cold Spring Harbor Perspectives in Medicine · 2017
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