4.3.1: The One-Exercise Rule: Choose the Lengthened Position

If a muscle is trained with only a single exercise, that exercise should place the muscle under high tension in the lengthened position (or mid-range). The evidence reviewed in Chapter 3—from Maeo et al. on hamstrings to Pedrosa et al. on biceps—is consistent: exercises that challenge the muscle at long lengths produce robust whole-muscle hypertrophy and tend to bias growth toward regions that shorter-length training misses [4,5]. The lengthened position provides the combination of active and passive tension that maximizes mechanotransduction across the widest portion of the muscle, and it avoids the active insufficiency that plagues many shortened-position exercises.

Examples of single-exercise selections that satisfy this rule:

Muscle	Single Exercise (Lengthened Emphasis)
Quadriceps	Leg Extension
Hamstrings	Seated leg curl
Biceps	Smith Machine Flat Press
Triceps	Overhead cable extension
Lateral delts	Cable Lateral Raises
Pectorals	Pec fly
Lats	Lat

Despite this being framed as a rule, it is not an absolute requirement. If you have a specific reason to choose a different exercise (e.g., injury, equipment availability, personal preference), that’s fine. But if you are building a minimalist routine with only one exercise per muscle, the lengthened position should be your default choice for maximizing hypertrophy.