The exercise protocol, designed to induce soreness in the elbow flexors, was modified from a previously published method of voluntary ECC [25]. During the week prior to initiating amino acid supplementation, the maximal voluntary strength of isometric contraction (MVC) in the non-dominant arm of each subject was measured at 1.57 rad (90°) of elbow
flexion. For the ECC protocol, Selleckchem MEK inhibitor subjects were seated on a bench with their arm positioned in front of their body and resting on a padded support, such that their shoulder was secured at a flexion angle of 0.79 rad (45°) and their forearm was maintained in the supinated position throughout the exercise. Subjects were repeatedly weight-loaded upon dumbbell lowering to achieve a 90% MVC (34.3 ± 1.3 Nm). Subjects performed six sets of five repetitions of elbow extension selleck chemicals from the flexed position at 90° to the fully extended position slowly over 5 s, while maintaining a constant speed of movement by following a verbal metronome provided by the investigator. After each extension, the investigator
returned the dumbbell to the starting position (90°) to prevent excess muscle activation induced by the weight. Subjects were permitted to rest for 3 s between repetitions and for 2 min between sets. The intensity of ECC at 90% MVC was determined on the basis of our preliminary experiments and likely induced natural muscle damage as all subjects found it difficult to lower the dumbbell at a constant speed during the later sets due to decreased muscle function. The subjects also required verbal encouragement from the investigator to maintain constant speed. Blood parameters of muscle damage Blood samples were collected from the antecubital vein at seven different time points: prior to amino acid supplementation, before exercise, immediately after exercise, at one to four days after exercise Reverse transcriptase (Day1–4) (Figure 1). On the day of exercise, blood was collected before supplement intake, and exercise
was started thereafter. Immediately after exercise, blood was collected again. In the four days following exercise, blood was collected at 07:00 before breakfast and amino acid intake. Serum was centrifuged for 30 min after the formation of a solid clot, and the plasma was immediately separated. The serum activities of creatine kinase (CK), lactate selleck dehydrogenase (LDH), and aldolase were analyzed and used as parameters of muscle damage, as described in the Japan Society of Clinical Chemistry consensus methods. Serum levels of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative stress-induced DNA damage, were measured before exercise and on Day 2 after exercise by competitive enzyme-linked immunosorbent assay (Highly Sensitive 8-OHdG Check ELISA kit; Japan Institute for the Control of Aging, Fukuroi, Japan) after purification with a 10-kDa filter (Nanosep®; Pall Corporation, NY, US).