Velocity Loss as a Critical Variable Determining the Adaptations to Strength Training

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• Resistance training (RT) effectiveness is influenced by training variables.
• Velocity loss (VL) during sets is a potential indicator of fatigue and training stimulus.
• Understanding optimal VL thresholds is crucial for maximizing performance adaptations.

Purpose of the Study:

• To compare the effects of four resistance training (RT) programs with distinct velocity loss (VL) thresholds (0%, 10%, 20%, 40%) on performance and physiological adaptations.
• To investigate the impact of varying VL on sprint, jump, strength, neuromuscular function, muscle hypertrophy, and architecture.

Main Methods:

• Sixty-four resistance-trained men participated in an 8-week full-squat RT program, assigned to VL0, VL10, VL20, or VL40 groups.
• Training involved 3 sets at 70-85% 1RM with 4-minute rests, differing in allowed VL per set.
• Pre- and post-training assessments included muscle hypertrophy/architecture, tensiomyography, sprint, jump, isometric strength, and fatigue tests.

Main Results:

• No significant differences in sprint, jump, or strength gains were observed across groups, despite varying total training volumes.
• Muscle hypertrophy significantly increased in VL20 and VL40 groups.
• VL40 showed impaired neuromuscular function, including slowed muscle delay time and reduced early rate of force development.

Conclusions:

• Higher VL thresholds (VL20, VL40) enhance muscle hypertrophy.
• Excessive VL (VL40) can lead to negative neuromuscular adaptations.
• Moderate VL thresholds are recommended to optimize strength adaptations and prevent detrimental neuromuscular changes.