Low-Load Resistance Training to Volitional Failure Induces Muscle Hypertrophy Similar to Volume-Matched, Velocity Fatigue

Journal of Strength and Conditioning Research: June 2022 - Volume 36 - Issue 6 - p 1576-1581 doi: 10.1519/JSC.0000000000003690


PURPOSE:

To investigate how resistance training (RT) to momentary muscle fatigue (MMF) using lighter loads affects acute responses and chronic muscle adaptations compared with lighter loads to velocity fatigue at equal work volume.


PROCEDURES:

Twenty-seven subjects performed 8 weeks of bench press twice weekly:


Group 1 (n = 9): Light load to MMF (LMMF).

@ 3 sets to MMF with 40% one repetition maximum (1-RM).


Group 2 (n = 8): Light load velocity fatigue (LVelF).

@ 3 sets to velocity fatigue (20% lifting velocity loss) with 40% 1-RM.


Group 3 (n = 10): Heavy load (HL).

@ 3 sets of 8 repetitions with at 80% 1-RM.


Muscle strength, hypertrophy, endurance, and power were measured at baseline and after the entire program was completed.


Also measured was muscle swelling and blood lactate after each RT bout to determine the acute response.


CONCLUSIONS:

No differences in total work volume between the LMMF and LVelF groups.


Similar results occurred between LMMF and LVelF whether it was acute muscle swelling, increase in blood lactate, chronic hypertrophy, or improved strength.


However, LMMF and LVelF triggered different responses to muscle function compared to HL:

  - LMMF and LVelF showed better acute responses and chronic endurance gains compared to HL.

  - LMMF and LVelF showed worse chronic strength gains compared to HL.


Overall, light load RT to MMF induces muscle hypertrophy similar to volume-matched velocity fatigue.


IN PLAIN ENGLISH:

Much of this depends on the number of repetitions completed at the point of the 20% velocity loss for the LVelF group. In this case, it was a similar volume compared to the LMMF group, thus most likely a similar quantity of muscle fibers was recruited and fatigued, thus the similar results.


In as much as 40% of a 1-RM can induce hypertrophy – and in light of the similar quantity of muscles fibers recruited and fatigued – the similar hypertrophy response would make sense in accordance with the previous comment.


Due to the lighter 40% 1-RM used for both the LMMF and LVelF groups compared to the heavier 80% 1-RM used for the HL group, common sense dictates less strength improvement would occur because the higher-tension producing 80% 1-RM naturally recruits a greater quantity of muscle fibers.