Author(s): TERZIS, G., BOGDANIS, G., LAMBROU, T., SMILIOS, I., PASCHALIS, V., Institution: NATIONAL AND KAPODISTRIAN UNIVERSITY OF ATHENS, Country: GREECE, Abstract-ID: 300

INTRODUCTION:
Resistance training induces significant increases in muscle mass and strength as well as vital health benefits; however, resistance exercise may also provoke transient muscle damage, resulting in temporary reductions in functional capacity and muscle strength as well as muscle soreness. Symptoms typically appear within 8–24 hours after the initial training session, peak between 24–48 hours and may persist for some days. Several exercise induced factors have been identified as triggers to muscle damage during resistance training including eccentric muscle actions, relatively long muscle lengths during training, high movement velocities or application of unaccustomed motor patterns. Nevertheless, it remains unknown whether performing each set of resistance exercise to momentary muscular failure constitutes a training related factor inducing exercise induced muscle damage. Aim of this study was to investigate potential muscle damage and loss of muscle strength following one resistance‑training session performed to momentary muscular failure using high loads in moderately trained young individuals.
METHODS:
Twelve moderately trained young females, unfamiliar to resistance training, performed unilateral elbow flexion at 85% of their maximal concentric strength for six sets to momentary muscular failure in each set (2 min rest between sets). One hour later, they performed the same total number of repetitions, with the contralateral arm, using the same load, identical range of motion and repetition tempo, but the total number of repetitions was distributed equally across 12 sets, therefore without reaching momentary failure. Maximal isometric elbow‑flexion strength, elbow range of motion, perceived muscle soreness, ultrasound echo‑intensity, and biceps brachii muscle thickness were assessed before the exercise intervention as well as 1, 24, 48, 72, and 96 hours after the intervention.
RESULTS:
In the arm trained to failure, maximal isometric strength decreased significantly (P≤0.05) and did not return to baseline even 96 hours post‑exercise. In contrast, strength in the non‑failure condition declined significantly immediately after exercise (P≤0.05) but returned to baseline within 24 hours. Perceived muscle soreness increased significantly at 24, 48, 72, and 96 hours post‑exercise for both arms (P≤0.05), with substantially greater soreness observed in the failure condition after the initial 24 hours. Ultrasound echo‑intensity of the biceps brachii muscle increased significantly at 72 and 96 hours only after the failure protocol (P≤0.05), indicating localized inflammation.
CONCLUSION:
Resistance exercise performed to momentary muscular failure in each set constitutes an independent factor leading to muscle damage and temporary reductions in muscle strength in individuals without prior resistance training experience.