In this episode of Hypertrophy Past & Present, Jake and Chris explore the use of circuits in hypertrophy training, starting with a 1960s circuit-style routine published by John McCallum. The episode examines how circuit-style training was used in the silver era, before transitioning into a physiology-first breakdown of when circuits might actually make sense for muscle growth today, and when they likely fall short.

Key topics include:
• A breakdown of McCallum’s Peripheral Heart Action (PHA) circuit routine
• Why inserting low-fatigue exercises between compounds can improve performance
• How circuits may reduce the exercise order effect across a workout
• When circuits might outperform straight sets (and when they won’t)
• How to structure circuits using clusters, low reps, and reps in reserve
• The practical limitations of circuits in busy gyms