Purpose. The purpose of the present study was to investigate possible differences between unilateral and bilateral strength training during ten weeks progressive hypertrophic strength training and six weeks detraining period. Furthermore, it was examined possible different individual responders in muscle hypertrophy during strength training and, how those different responders would behave during the detraining phase following the training period.
Methods. The present intervention included ten weeks of progressive hypertrophic resistance training followed by six weeks of detraining in healthy young men (n=24). Ultrasound was used to measure vastus lateralis (VL) muscle cross-sectional area (CSA) and triceps brachii (TB) thickness. Maximal bilateral and unilateral lower and upper body isometric forces as well as maximal dynamic unilateral and bilateral concentric maximum forces in leg and bench press were measured. The subjects trained three times per a week. The subjects received an i
ndividual example nutritional plan before the start of the intervention and they received protein and carbohydrate supplementation after every training session.
Results. VLCSA increased in the total group from 31.1±5.7cm to 35.1±5.0cm (p=0.013) and leg press 1RM from 154.6±24.9kg to 178.5±25kg (p<0.0001) after ten weeks of strength training. The subjects were split to three groups according to the increase in VLCSA: High responders >15% (n=10), Medium responders 15-5% (n=6) and Low responders <5% (n=8). High responders were the only ones to have a significant change in VLCSA from pre to mid, pre to post, pre to detraining 1, pre to detraining 2 and post to detraining 2. VLCSA increased in High responders by 22.3% ±7.0 during training and decreased by -9.3%±5.7 during detraining and 1RM by +20.5±12.5% and by -2.1±3.1%, respectively. The corresponding values for Medium responders were +8.7±6.0% and -4.7±3.3% for VLCSA, and +14.1±11.3% and -1.9±4.3% for 1RM, and for Low responders -2.3±5.9% and -0.5±8.4% for VLCSA and +12.6±11.5% and +0.19±3.4 for 1RM, respectively. All dynamic strength values were statistically significantly changed from pre to post for both groups. The unilateral group improved isometric strength statistically significantly from pre to post for isometric left and right leg, and also for bilateral leg press. The bilateral group only increased significantly in isometric bilateral leg press force from pre to post. The lean mass increases (total lean mass, arms, legs) were statistically significant for both groups.
Conclusion. High responders tend to lose VLCSA and dynamic bilateral strength somewhat faster than Low responders during the detraining phase. In addition, muscle hypertrophy in High responders was observed to appear already during earlier weeks of training. There were no statistically significant differences between the unilateral and bilateral groups in any variables. Both training types seem to lead to similar gains in terms of muscle hypertrophy and strength.
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