A Comparison of Techniques for Estimating and Detecting Changes in Skeletal Muscle Cross-Sectional Area

Abstract

Muscle biopsy and subsequent histological analysis of muscle fibers is a criterion technique for determining hypertrophy of skeletal muscle in resistance- and endurance-trained individuals. However, due to the training necessary to complete the biopsy, and the invasive nature of the biopsy itself, alternative methods for depicting muscle fiber hypertrophy offer increased ability to gather data discerning skeletal muscle hypertrophy. Furthermore, such procedures require less training and are noninvasive. PURPOSE: This project sought to determine if estimated mid-thigh whole muscle cross-sectional area (CSA) is related to muscle fiber CSA from muscle biopsies. METHODS: Twenty-nine resistance-trained men (age: 21 ± 2 yrs, weight: 83.6 ± 11.0 kg, height: 178.7 ± 8.1 cm) underwent six weeks of total-body resistance training. Muscle biopsies were taken from the Vastus lateralis prior to and following training. Mid-thigh circumference and skinfold measurements (anterior, posterior, medial, and lateral) were used to estimate whole muscle mid-thigh cross-sectional area using the methods of Moritani and deVries. RESULTS: Whole-muscle CSA did not significantly increase from pre- (272.737 ± 37.401 cm) to post-training (277.286 ± 29.474 cm; p = 0.201). Muscle fiber CSA did not significantly increase from pre- (4068 ± 865 μm) to post-training (4221 ± 704 μm; p = 0.368). Additionally, pre muscle fiber CSA did not correlate to pre whole-muscle CSA (r = 0.029, p = 0.882). Also, Muscle fiber CSA percent change did not correlate with whole-muscle CSA percent change (r = -0.064, p = 0.741). CONCLUSION: Estimated whole-muscle CSA and muscle fiber CSA do not appear to correlate well. A lack of a relationship between the changes in these measurements following hypertrophy are puzzling and warrant further study.