Muscle Hypertrophy Responses to Changes in Training Volume: A Retrospective Analysis

Area of Science:

• Exercise Physiology
• Muscle Physiology
• Sports Science

Background:

• Resistance training is a primary stimulus for muscle hypertrophy.
• Understanding the dose-response relationship between training volume and muscle growth is crucial for optimizing training programs.
• Previous research has explored this relationship, but findings in already trained individuals require further clarification.

Purpose of the Study:

• To assess the association between changes in weekly training volume (number of sets) and muscle thickness changes in the biceps and triceps brachii muscles.
• To investigate if different magnitudes of training volume increase correlate with varying degrees of muscle hypertrophy in resistance-trained subjects.

Main Methods:

• Retrospective analysis of training data from sixty-eight resistance-trained participants.
• Spearman correlation was used to determine the relationship between training volume alterations and muscle thickness changes.
• K-cluster analysis categorized participants into groups based on the percentage increase in weekly sets (<0%, 0-50%, >50%).

Main Results:

• Moderate correlation (r_s=0.44) between training volume changes and biceps muscle thickness (MT_BB).
• Weak correlation (r_s=0.35) between training volume changes and triceps muscle thickness (MT_TB).
• Significant differences in muscle thickness were observed between the <0% and >50% increase groups for both MT_BB and MT_TB.

Conclusions:

• Muscle hypertrophy of the upper limbs in trained individuals is weakly to moderately associated with changes in training volume.
• While a substantial increase in training volume (>50%) may lead to greater muscle thickness changes compared to no increase or a small increase, the overall association remains moderate at best.
• The findings suggest that factors beyond just the number of sets may significantly influence muscle hypertrophy in trained populations.