Functional changes of human quadriceps muscle injured by eccentric exercise

Abstract

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion). The isometric torque of the quadriceps (knee at 90º flexion) decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63%) and VMO (66%) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.

Effect of Kinesiotaping Intervention on Knee Muscle Strength and Delayed Onset Muscle Soreness Pain Following Eccentric Fatigue Training

“…The study concluded that VL muscle recovers a week later, and returns to its pre-exercise level at the end of the 2nd week, and was in a better level compared to its previous level (5). Similarly, in our study, muscle strength and DOMS pain reached the worst level on the 2nd day.…”

“…DOMS pain and loss of strength arises from damage to muscle fibers, muscle fatigue due to lactic acid and creatine kinase accumulation, degradation of connective tissue and fascia structure, muscle spasms, decrease of afferent inputs and inflammation (2,(5)(6)(7)(17)(18)(19)(20)(21). DOMS and strength loss reach their maximum value within 24-48 hours following eccentric fatigue protocol or eccentric training (2,(5)(6)(7).…”

“…DOMS and strength loss reach their maximum value within 24-48 hours following eccentric fatigue protocol or eccentric training (2,(5)(6)(7). According to a study by Cheung et al, one of the reasons why DOMS pain reaches a maximum value within 48 hours is the increase in the permeability of the muscle cell membranes via creatine kinase levels as a result of muscle damage.…”

“…During eccentric training, muscular movement acts like shock absorbent structures, the length of the muscle extends, and this extension causes a negative workload (1,2). While eccentric training improves the muscle strength, it causes damage in the skeletal muscle fibers (1,(3)(4)(5). There are several theories that explain the exercise induced Delayed Onset Muscular Soreness (DOMS) mechanism.…”

“…Monocytes convert to macrophages and accumulate at the injury site and this reaction sensitizes the Type III and Type IV nerve endings in 24-48 hours (6). There are more reports that explain the reason behind the strength reduction and Delayed Onset Muscular Soreness (DOMS), which are related to acute inflammatory reaction in the muscles of especially sedentary individuals after eccentric training (4)(5)(6)(7)(8).…”