Velocity Training Revisited: 20% or 40% Reduction in Bar Velocity on Barbell Squats - What'll Yield Greater Gains?

Squats, squats and, you guessed it squats - That's all the subjects did in this 8-week study W/ trained young men.

Back in the early days of the SuppVersity, I reported the results of a resistance training study which showed that interrupting your sets, when you can no longer perform the exercise at maximal velocity yielded quite astonishing increases in muscle gains - despite stopping several reps away from failure.

Spanish researchers have now attempted to gain further insight into the adaptations brought about by training close to muscle failure vs not to failure, and compared the effects of two RT programs that only differed in the magnitude of repetition velocity loss allowed in each set (20% vs 40%) on structural and functional adaptations.
The scientists hypothesized that "despite a remarkably lower training volume, improvements in strength and performance will be greater with the RT program allowing only a 20% reduction in repetition velocity, whereas a 40% velocity loss will result in greater muscle hypertrophy" (). Or, in other words, the scientists expected that ...

• approaching failure would increase strength gains, 
• while shying away from it would increase hypertrophy. 

The results I've plotted for you in Figure 2 do yet show a different image. Over the 16 workouts (2 workouts per week for the twenty-four resistance-trained young and healthy men | full squat 1RM 106.2 +/- 13.0 kg) the subjects had done identical workouts - albeit with different termination conditions: While the 20% group terminated their set when they reached a velocity loss of only 20%, the 40% group kept going until a lift that would usually have taken them 1s took them 1.5s and thus 40% longer than usual. The only exercise that was performed was the barbell squat.

Figure 2: As you can see, the VL20 did - as it was expected and intended fewer reps, but at a higher velocity than the VL40 group who terminated their sets only after they had slowed down by >40% (Pareja-Blanco 2017).

Sessions were performed in a research laboratory under the direct supervision of the investigators, at the same time of day (+/- 1 h) for each subject and under controlled environmental conditions (20 °C and 60% humidity).
Subjects were required not to engage in any other type of strenuous physical activity, exercise training, or sports competition for the duration of the present investigation. Both VL20 and VL40 groups were assessed on two occasions: 48 h before (Pre) and 72 h after (Post) the 8-week training intervention. Training compliance was 100% of all sessions for the subjects that completed the intervention.

Figure 2: Changes in muscle volume due to 8 weeks of velocity-based resistance training for: (a) Whole quadriceps femoris; (b) rectus femoris (RF); (c) vastus medialis (VM); and (d) VL+VI (Pareja-Blanco 2017).

The scientists did not find their hypothesis confirmed when they analyzed their results: The expected strength advantage for the VL40 group was not observed:

"Following the training intervention, statistically significant increases were observed in 1RM strength (18.0% and 13.4%), AV (12.5% and 6.0%), and AV<1 (21.7% and 13.7%) for VL20 and VL40 groups, respectively" (Pareja-Blanco 2017).

Similarly, the quadriceps femoris volume (Fig. 3a) was increased by 6.0% (time effect P < 0.05). This was explained by a significant increase of VM volume (Fig. 3c) in both groups. In contrast to the scientists hypothesis, however, there was a small, but measurable benefit from doing more reps and going closer to failure for the sum of vastus lateralis (VL) + vastus intermedius (VI) gains, which increased exclusively in the VL40 group (group x time interaction, P = 0.05).
References:

• Morán-Navarro, Ricardo, et al. "Movement velocity as a measure of level of effort during resistance exercise." The Journal of Strength & Conditioning Research (2017).
• Pareja‐Blanco, F., et al. "Effects of velocity loss during resistance training on athletic performance, strength gains and muscle adaptations." Scandinavian journal of medicine & science in sports (2016).
• Tan, Benedict. "Manipulating Resistance Training Program Variables to Optimize Maximum Strength in Men: A Review." The Journal of Strength & Conditioning Research 13.3 (1999): 289-304.