Strength Training's Chronic Effects on Muscle Architecture Parameters of Different Arm Sites

Abstract

Strength training generates alterations in muscle geometry, which can be monitored by imaging techniques as, for example, the ultrasound (US) technique. There is no consensus about the homogeneity of hypertrophy in different muscle sites. Therefore, the purpose of this study was to compare the muscle thickness (MT) and pennation angle (PA) in 3 different sites (50, 60, and 70% of arm length) of the biceps brachii and triceps brachii after 12 weeks of strength training. Forty-nine healthy untrained men were divided into 2 groups: Training Group ([TG, n = 40] 29.90 ± 1.72 years; 79.53 ± 11.84 kg; 173 ± 0.6 cm) and Control Group (n = 9 25.89 ± 3.59 years; 73.96 ± 9.86 kg; 171 ± 6 cm). The TG underwent a strength training program during 12 weeks, which included exercises such as a free-weight bench press, machine lat pull-down, triceps extension in lat pull-down, and standing free-weight biceps curl with a straight bar. A US apparatus was used to measure the PA and MT at the 3 sites. The maximal voluntary isometric contraction (MVC) test was conducted for each muscle group. After 12 weeks of training, a significant difference was observed between MT in biceps brachii, with an improvement of 12% in the proximal site, whereas the distal site increased by only 4.7% (p < 0.05). For the long head of the triceps brachii, the MT and PA at the 3 sites presented significant increases, but no significant variation was observed among them, probably because of the pennated-fiber arrangement. The MVC increased significantly for both muscle groups. The results indicated that the strength training program was efficient in promoting hypertrophy in both muscles, but with dissimilar responses of the pennated and fusiform muscle architecture at different arm sites.

Triceps Brachii Muscle Strength and Architectural Adaptations with Resistance Training Exercises at Short or Long Fascicle Length

“…While strength training induced significant increases in strength, the muscle architecture of the long head of the triceps did not change significantly, which is in accordance with a previous study [21]. Interestingly, in this previous study, there was a uniform architectural adaptation at 50% and 60% of the triceps brachii length, as found here.…”

Training-induced changes in architecture of human skeletal muscles: Current evidence and unresolved issues

“…Studies have found changes in the pennation angle of each muscle of the quadriceps femoris 68) , as well as VL, RF 83,84) , BF 55) , MG 85) , LG 59,86) , TB 70,73,87,88) , biceps brachii 89) , brachialis 89) and supraspinous 90) . A positive correlation was shown between the absolute values of muscle thickness and pennation angle for TB 73) and each muscle of the quadriceps femoris 68) before and after the interventions.…”

Correlation between lateral abdominal, rectus femoris, and triceps brachii muscle thickness and endurance during prone bridge exercise in healthy young adults

“…The correlations between muscle thickness, cross sectional area, and hold time of the prone bridge position were determined using Pearson's correlation coefficient. According to a citation for this prior study, 0.00<r< 0.19 represent very weak correlation, 0.20<r<0.39 weak, 0.40<r<0.59 moderate, 0.60<r<0.79 strong and 0.80<r< 1.00 very strong [18]. Values were considered statistically significant at p<0.05.…”

“…Triceps brachii thickness was estimated from ultrasound images, with the probe transversally positioned. The muscle thickness was defined as the distance from the interface between the muscle and bone tissue, to the interface between the muscle and fat tissue [18]. Resting triceps brachii thickness was measured with the subject prone on a bed; contraction thickness was measured as the prone subject lowered the arm to the floor and then extended the shoulder to a horizontal position with a 3-kg sandbag on the wrist.…”