Study Finds Lengthened Partial and Full Range of Motion Resistance Training Produce Similar Muscle Growth in Trained Men
A crossover study of resistance-trained men found that lengthened partial range of motion (LP) and full range of motion (FULL) leg training produced comparable vastus lateralis hypertrophy and molecular responses over 8 weeks. Both protocols triggered similar changes in gene expression and anabolic signaling pathways (mTORC1 and Hippo) acutely, and neither protocol produced significantly greater quadriceps muscle growth chronically. However, secondary findings suggested LP training may produce greater hamstring hypertrophy, indicating exercise selection could influence where differential adaptations occur.
The study comprised two experiments: the first used muscle biopsies from 8 trained men to assess acute transcriptomic and anabolic signaling responses at 0, 3, and 24 hours post-exercise, while the second enrolled 16 trained men in an 8-week, twice-weekly within-subject intervention where each leg was assigned to either LP or FULL training across leg press, leg extension, and lying leg curl exercises. Vastus lateralis (VL) muscle cross-sectional area, fiber size, myonuclei counts, satellite cell numbers, and total RNA content were assessed via MRI and biopsy before and after the intervention. VL summed muscle cross-sectional area increased substantially over time (mean change: 9.3 cm², 95% CI [6.8, 11.8]), but the difference between LP and FULL conditions was small and non-significant (LP-FULL: -1.4 cm², 95% CI [-6.1, 3.8], P=0.640). No significant between-condition differences were found for any cellular-level outcome, including type I and II fiber cross-sectional area, myonuclei, satellite cells, or RNA content. A secondary analysis of hip and thigh muscles provided suggestive evidence that LP training produced greater whole hamstring hypertrophy than FULL (LP-FULL: 3.9 cm², 95% CI [-0.2, 7.9], P=0.058), though this finding did not reach conventional statistical significance. The authors conclude that LP and FULL training are broadly equivalent for quadriceps adaptations in trained men, but that exercise-specific mechanics may drive differential outcomes in adjacent muscle groups.
What's missing
The study's own limitations include a relatively small sample size (n=8 and n=16), a short 8-week intervention duration that may not capture longer-term divergence between protocols, and the use of only male participants, limiting generalizability to women. The hamstring finding (P=0.058) did not reach conventional significance and should be interpreted cautiously as a secondary, exploratory result. The study also does not address whether results would differ in untrained individuals, who may respond differently to range-of-motion manipulations.
What different sources said
- bioRxivCenter
Acute molecular and chronic vastus lateralis adaptations to lengthened partial versus full range of motion resistance training in previously trained males
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