The Effect of Myofibril and Sarcoplasmic Hypertrophy Training on Muscle Hypertrophy and Strength

Background This study aimed to investigate the effects of myofibrillar and sarcoplasmic hypertrophy training on muscle hypertrophy, strength, and selected anthropometric characteristics. Methods A total of 30 healthy male volunteers aged 20-35 years participated in the study. Participants were randomly assigned to myofibrillar (n=15) and sarcoplasmic (n=15) hypertrophy training groups. The study employed a pretest-posttest design over eight weeks of myofibrillar and sarcoplasmic training. Anthropometric measurements included height, weight, body mass index (BMI), and circumferences of the shoulder, chest, waist, upper arm, and thigh. Pectoralis major (PM), latissimus dorsi (LD), and quadriceps femoris (QF) muscle thickness were measured using ultrasonography. Strength measurements included bench press, squat, and deadlift 1 RM before and after training. Paired sample t-tests were used to compare pre-test and post-test data within groups, while independent sample t-tests were used to compare differences between groups. Results were evaluated at a 95% confidence interval and 0.05 significance level. Results Significant differences were observed in the pretest-posttest ultrasound data difference means of the dominant side PM (t = -2.321 p < .05) and LD (t = -2.699 p < .05) muscles between the myofibrillar and sarcoplasmic hypertrophy training groups. Significant differences were also found in the non-dominant side PM (t = -2.352 p < .05) and LD (t = -2.723 p < .05) muscles. Myofibrillar training group showed significant improvements in bench press (t = -9.431 p < .05), squat (t = -2.477 p < .05), and deadlift strength (t = -5.041 p < .05), while the sarcoplasmic group showed significant improvements in bench press (t = -3.287 p < .05) and deadlift strength (t = -2.779 p < .05) in the pretest-posttest. Conclusion Myofibrillar hypertrophy training resulted in greater hypertrophy compared to sarcoplasmic training according to muscle ultrasonography images.