Cross-education and detraining effects of eccentric vs. concentric resistance training of the elbow flexors

Background: Unilateral resistance training increases the strength of the contralateral non-trained homologous muscles known as the cross-education effect. We tested the hypothesis that unilateral eccentric resistance training (ET) would induce greater and longer-lasting cross-education effect when compared with concentric resistance training (CT). Methods: Young (20–23 y) participants were allocated to ET (5 males, 4 females) or CT (5 males, 4 females) group that performed unilateral progressive ET or CT of the elbow flexors, twice a week for 5 weeks (10 sessions) followed by a 5-week detraining, and control group (7 males, 6 females) that did not perform any training. Maximum voluntary isometric contraction torque of the elbow flexors (MVIC), one-repetition maximum of concentric dumbbell curl (1-RM), and biceps brachii and brachialis muscle thickness (MT) were measured from the trained and non-trained arms before, several days after the last training session, and 5 weeks later. A ratio between the trained and non-trained arms for the change in MVIC or 1-RM from pre- to post-training (cross-body transfer ratio) was compared between ET and CT groups. Results: The control group did not show significant changes in any variables. Both ET and CT increased (P \u3c 0.05) MVIC (22.5 ± 12.3 % vs. 26.0 ± 11.9 %) and 1-RM (28.8 ± 6.6 % vs. 35.4 ± 12.9 %) of the trained arm without a significant difference between groups. MVIC was maintained after detraining for ET but returned to the baseline for CT, and 1-RM was maintained after detraining for both ET and CT. For the non-trained arm, MVIC (22.7 ± 17.9 % vs. 12.2 ± 10.2 %) and 1-RM (19.9 ± 14.6 % vs. 24.0 ± 10.6 %) increased similarly (P \u3e 0.05) after ET and CT, and MVIC returned to the baseline after detraining, but 1-RM was maintained for both groups. An increase (P \u3c 0.05) in MT was found only after ET for the trained arm (7.1 ± 6.1 %). The cross-body transfer ratio for MVIC was greater (P \u3c 0.05) for ET (90.9 ± 46.7 %) than CT (49.0 ± 30.0 %). Conclusions: These results did not support the hypothesis and showed similar changes in the most of the variables between ET and CT for the trained and non-trained arms, and strong cross-education effects on MVIC and 1-RM, but less detraining effect after ET than CT on MVIC of the trained arm. Trial registration: University Hospital Medical Information Network Clinical Trials Registry (UMIN000044477; Jun 09, 2021)

Joint angles in elbow flexor unilateral resistance exercise training determine its effects on muscle strength and thickness of trained and non-trained arms

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, = 12); flexed joint training (80°-130°; FLE, = 12); and non-training control ( = 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 ( \u3c 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 ( \u3c 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

The Acute Effect of Foam Rolling on Eccentrically-Induced Muscle Damage

Previous studies have shown significant improvement in muscle soreness and muscle function loss after 300-s foam rolling intervention two days after intense exercise. However, this duration is assumed to be too long, so investigating the effect of short-term duration foam rolling intervention on an eccentrically-damaged muscle is needed. This study aimed to eccentrically induce muscle damage in the leg extensors, and to detect the acute effect of 90-s foam rolling on muscle soreness and muscle function of the quadriceps muscle. We enrolled 17 healthy and nonathlete male volunteers. They performed a bout of eccentric exercise of the knee extensors with the dominant leg and received 90-s foam rolling intervention of the quadriceps two days after the eccentric exercise. The dependent variables were measured before the eccentric exercise (baseline), and before (preintervention) and after foam rolling intervention (postintervention), two days after the eccentric exercise. The results show that the preintervention muscle soreness and muscle strength values were significantly increased, compared with the baseline values, whereas the postintervention values were significantly decreased, compared with the preintervention values. Furthermore, 90-s of foam rolling intervention could improve muscle soreness and muscle function loss

Relationship between nordic hamstring strength and maximal voluntary eccentric, concentric and isometric knee flexion torque

Nordic hamstring exercise is performed to prevent knee flexor muscle strain injuries and used to assess their injury risks. However, what exactly Nordic hamstring strength indicates is not clear. We investigated the relationship between Nordic hamstring strength and maximal voluntary contraction (MVC) torque of the knee flexors measured by an isokinetic dynamometer. Sixteen healthy young men who had not experienced hamstring strain injuries participated in the study. In Nordic hamstring, each participant was instructed to lean forward as far as possible in 3 s (approximately 30/s), and force at the ankle joint of the dominant leg was measured during the movement. The force was multiplied by lower leg length and converted into torque. MVC torque of the knee flexors was measured isometrically at 30, 45, 60, and 90 knee flexion joint angles, and concentrically and eccentrically at 30/s and 60/s in 10–90 knee flexion for the dominant leg in a prone position. Correlations among the dependent variables were assessed using Pearson’s correlation coefficients. Peak Nordic hamstring torque ranged 96.8–163.5 Nm, and peak MVC eccentric torque ranged 50.7–109.4 Nm at 30/s and 59.2–121.2 Nm at 60/s. No significant correlations were evident between the peak Nordic hamstring torque and peak eccentric knee flexion torque (r = 0.24–0.3, p = 0.26–0.4). This was also the case for the Nordic hamstring torque and MVC torque of isometric (r = −0.03–0.1, p = 0.71–0.92) and concentric contractions (r = 0.28–0.49, p = 0.053–0.29). These results show that Nordic hamstring strength is not associated with the knee flexor torque measured by an isokinetic dynamometer. It may be that other factors than static and dynamic hamstring strengths affect Nordic hamstring strength

Local and non-local effects of foam rolling on passive soft tissue properties and spinal excitability

In sports and clinical settings, roller massage (RM) interventions are used to acutely increase range of motion (ROM); however, the underlying mechanisms are unclear. Apart from changes in soft tissue properties (i.e., reduced passive stiffness), neurophysiological alterations such as decreased spinal excitability have been described. However, to date, no study has investigated both jointly. The purpose of this trial was to examine RM’s effects on neurophysiological markers and passive tissue properties of the plantar flexors in the treated (ROLL) and non-treated (NO- ROLL) leg. Fifteen healthy individuals (23 ± 3 years, eight females) performed three unilateral 60-s bouts of calf RM. This procedure was repeated four times on separate days to allow independent assessments of the following outcomes without reciprocal interactions: dorsiflexion ROM, passive torque during passive dorsiflexion, shear elastic modulus of the medial gastrocnemius muscle, and spinal excitability. Following RM, dorsiflexion ROM increased in both ROLL (+19.7%) and NO-ROLL (+13.9%). Similarly, also passive torque at dorsiflexion ROM increased in ROLL (+15.0%) and NO-ROLL (+15.2%). However, there were no significant changes in shear elastic modulus and spinal excitability (p > 0.05). Moreover, significant correlations were observed between the changes in DF ROM and passive torque at DF ROM in both ROLL and NO-ROLL. Changes in ROM after RM appear to be the result of sensory changes (e.g., passive torque at DF ROM), affecting both rolled and non-rolled body regions. Thus, therapists and exercise professionals may consider applying remote treatments if local loading is contraindicated