Elbow Joint Angles in Elbow Flexor Unilateral Resistance Exercise Training Determine Its Effects on Muscle Strength and Thickness of Trained and Non-trained Arms

Abstract

The present study compared two unilateral arm curl resistance exercise protocols with a different starting and finishing elbow joint angle in the same ROM for changes in elbow flexors strength and muscle thickness of the trained and non-trained arms. Thirty-two non-resistance trained young adults were randomly assigned to one of the three groups: extended joint training (0°–50°; EXT, n = 12); flexed joint training (80°–130°; FLE, n = 12); and non-training control (n = 8). The exercise training was performed by the dominant arms twice a week for 5 weeks with gradual increases in the training volume over 10 training sessions, and the non-dominant (non-trained) arms were investigated for the cross-education effect. Maximal voluntary contraction torque of isometric (MVC-ISO), concentric (MVC-CON), and eccentric contractions (MVC-ECC), and thickness (MT) of biceps brachii and brachialis of the trained and non-trained arms were assessed at baseline and 4–8 days after the last training session. The control group did not show significant changes in any variables. Significant (P < 0.05) increases in MVC-ISO torque (16.2 ± 12.6%), MVC-CON torque (21.1 ± 24.4%), and MVC-ECC torque (19.6 ± 17.5%) of the trained arm were observed for the EXT group only. The magnitude of the increase in MT of the trained arm was greater (P < 0.05) for EXT (8.9 ± 3.9%) than FLE (3.4 ± 2.7%). The cross-education effect was evident for MVC-ISO (15.9 ± 14.8%) and MVC-CON (16.7 ± 20.0%) torque of the EXT group only. These results suggest that resistance training at the extended elbow joint induces greater muscle adaptations and cross-education effects than that at flexed elbow joint.

Regional hypertrophy: the role of exercise resistance profile in trained women

“…Even if the current results are in line with previous research (Sato et al 2021), other authors have found no differences in regional hypertrophy of the arm muscles after performing preacher curls (Drummond et al 2016). However, in this study the special equipment used placed the major di culty when the biceps brachii was in a shortened position, and all the subjects performed preacher curls (not any other exercise, with any special kind of resistance) which shows the importance of mechanical stimuli and resistance pro les for regional hypertrophy (Franchi et al 2018b).…”

“…This data shows once again the in uence of contraction type in regional hypertrophy, and outlines the importance of standardizing the time spent performing concentric or eccentric actions during a repetition in regional hypertrophy studies to avoid confusion factors. However, it should be noted that the distal part of the arm is the biggest one (Matta et al 2011;Sato et al 2021), and for that reason it is also the one we should expect to grow the most (at least in terms of absolute growth). In fact, growth in the most distal part of the arm can be found in 4 studies (including the present one), while the rest of the regions do not always grow (Matta et al 2011;Yasuda et al 2015;Sato et al 2021).…”

Does Varying Resistance Exercises Promote Superior Muscle Hypertrophy and Strength Gains? A Systematic Review

“…The authors postulated that this finding was likely because of the implementation of the incline dumbbell curl; given the more elongated position of the biceps, this exercise potentially favors stretch-mediated hypertrophy (14,42). This hypothesis is supported by emerging evidence demonstrating the superiority of training certain muscles in more stretched positions (28,38,41). Hence, these 2 studies (14,20) taken together with previous findings (5,10) suggest that exercise variation should be carefully planned and implemented to optimize benefits from exercise variation.…”

Partial range of motion and muscle hypertrophy: not all ROMs lead to Rome

“…8 Several studies published subsequent to that paper have shown greater hypertrophy at longer versus shorter muscle lengths in dynamic training of the hamstrings 9 and biceps brachii. 10 Most recently, Pedrosa et al 7 found that pROM knee extension training at a long muscle length was at least as effective, and in some cases superior, in eliciting increases in quadriceps CSA compared to fROM training.…”