Yiannis Michailidis

Time course of changes in performance and inflammatory responses after acute plyometric exercise.

Chatzinikolaou, A, Fatouros, IG, Gourgoulis, V, Avloniti, A, Jamurtas, AZ, Nikolaidis, MG, Douroudos, I, Michailidis, Y, Beneka, A, Malliou, P, Tofas, T, Georgiadis, I, Mandalidis, D, and Taxildaris, K. Time course of changes in performance and inflammatory responses after acute plyometric exercise. J Strength Cond Res 24(5): 1389-1398, 2010-The objectives of the present investigation were to study the inflammatory and performance responses after an acute bout of intense plyometric exercise during a prolonged recovery period. Participants were randomly assigned to either an experimental group (P, n = 12) that performed intense plyometric exercises or a control group (C, n = 12) that rested. The delayed onset of muscle soreness (DOMS), knee range of motion (KROM), creatine kinase (CK) and lactate dehydrogenase (LDH) activities, white blood cell count, C reactive protein (CRP), uric acid (UA), cortisol, testosterone, IL-6, IL-1b strength (isometric and isokinetic), and countermovement (CMJ) and static (SJ) jumping performance were measured at rest, immediately postexercise and at 24, 48, 72, 96, and 120 hours of recovery. Lactate was measured at rest and postexercise. Strength remained unchanged throughout recovery, but CMJ and SJ declined (p < 0.05) by 8-20%. P induced a marked rise in DOMS, CK, and LDH (peaked 24-48 hours postexercise) and a KROM decline. An acute-phase inflammatory response consisting of leukocytosis (postexercise and at 24 hours), an IL-6, IL-1b, CRP, and cortisol elevation (during the first 24 hours of recovery) and a delayed increase of UA (peaked at 48 hours) and testosterone (peaked at 72 hours) was observed in P. The results of this investigation indicate that performing an acute bout of intense plyometric exercise may induce a short-term muscle damage and marked but transient inflammatory responses. Jumping performance seems to deteriorate for as long as 72 hours postexercise, whereas strength appears to remain unchanged. The acute-phase inflammatory response after a plyometric exercise protocol appears to follow the same pattern as in other exercise models. These results clearly indicate the need of sufficient recovery between successive plyometric exercise training sessions.

Time-Course of Changes in Oxidative Stress and Antioxidant Status Responses Following a Soccer Game

Fatouros, IG, Chatzinikolaou, A, Douroudos, II, Nikolaidis, MG, Kyparos, A, Margonis, A, Michailidis, Y, Vantarakis, A, Taxildaris, K, Katrabasas, I, Mandalidis, D, Kouretas, D, and Jamurtas, AZ. Time-course of changes in oxidative stress and antioxidant status responses following a soccer game. J Strength Cond Res 24(12): 3278-3286, 2010-Exercise-induced muscle damage is associated with an acute-phase inflammatory response characterized by phagocyte infiltration into muscle and free radical production. Although soccer includes intense eccentric muscle actions that cause muscle damage, the oxidative stress responses after a soccer game are currently unknown. The present investigation attempted to determine the responses of circulating levels of oxidative stress and antioxidant status markers during recovery from a soccer game. Twenty soccer players (experimental group) were assigned to 2 different teams that competed against each other (2 × 45 minutes). Ten other players served as controls (rested). Creatine kinase (CK) activity, uric acid, leukocyte count, malondialdehyde (MDA), protein carbnyls (PC), reduced (GSH) and oxidized glutathione (GSSG), antioxidant capacity (TAC), catalase, glutathione peroxidase activity (GPX), delayed-onset of muscle soreness (DOMS), and anaerobic performance (speed, vertical jump performance) were measured before and following (immediately post, 24 hours, 48 hours, 72 hours) the game. Performance deteriorated (2-17%, p < 0.05) throughout recovery. Leukocytosis developed (p < 0.05) immediately following the game and at 24 hours. Both CK and DOMS (3-8-fold, p < 0.05) increased from baseline and remained elevated (p < 0.05) through 48 hours. Thiobarbituric acid reactive substances (TBARS), PC, uric acid, GPX, and TAC increased (13-67%, p < 0.05) throughout recovery, whereas catalase was elevated (38%, p < 0.05) only immediately after the game. GSH/GSSG declined (17-75%, p < 0.05) throughout recovery. Our results suggest that oxidative stress is markedly upregulated by a soccer game, probably as a part of the exercise-induced inflammatory response, and is accompanied by a marked deterioration of anaerobic performance for as long as 72 hours.

Effects of L-carnitine on oxidative stress responses in patients with renal disease.

PURPOSE Hemodialyzed patients demonstrate elevated oxidative stress and reduced functional status. Exercise induces health benefits, but acute exertion up-regulates oxidative stress responses in patients undergoing hemodialysis. Therefore, the aim of the present study was to examine the effect of L-carnitine supplementation on i) exercise performance and ii) blood redox status both at rest and after exercise. METHODS Twelve hemodialysis patients received either L-carnitine (20 mg kg(-1) i.v.) or placebo in a double-blind, placebo-controlled, counterbalanced, and crossover design for 8 wk. Participants performed an exercise test to exhaustion before and after supplementation. During the test, V˙O2, respiratory quotient, heart rate, and time to exhaustion were monitored. Blood samples, collected before and after exercise, were analyzed for lactate, malondialdehyde, protein carbonyls, reduced and oxidized glutathione, antioxidant capacity, catalase, and glutathione peroxidase activity. RESULTS Blood carnitine increased by L-carnitine supplementation proportionately at rest and after exercise. L-carnitine supplementation increased time to fatigue (22%) and decreased postexercise lactate (37%), submaximal heart rate, and respiratory quotient but did not affect V˙O2peak. L-carnitine supplementation increased reduced/oxidized glutathione (2.7-fold at rest, 4-fold postexercise) and glutathione peroxidase activity (4.5% at rest, 10% postexercise) and decreased malondialdehyde (19% at rest and postexercise) and protein carbonyl (27% at rest, 40% postexercise) concentration. CONCLUSIONS Data suggest that a 2-month L-carnitine supplementation may be effective in attenuating oxidative stress responses, enhancing antioxidant status, and improving performance of patients with end-stage renal disease.

Time of sampling is crucial for measurement of cell-free plasma DNA following acute aseptic inflammation induced by exercise.

OBJECTIVES To determine the time-course changes of cell-free plasma DNA (cfDNA) following heavy exercise. METHODS cfDNA concentration, C-reactive protein levels (hs-CRP), uric acid concentration (UA), creatine kinase activity (CK) were measured before and post-exercise (immediately post, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 8h, 10h, 24h). RESULTS cfDNA increased (15-fold) 30-min post-exercise and normalized thereafter. hs-CRP increased (56%, p<0.001) 1h post-exercise, remained elevated throughout recovery (52-142%, p<0.0001), and peaked (200% rise, p<0.0001) at 24h post-exercise. UA and CK increased (p<0.05), immediately post-exercise, remained elevated throughout recovery (p<0.0001), and peaked (p<0.0001) at 24h of post-exercise recovery. CONCLUSIONS cfDNA sampling timing is crucial and a potential source of error following aseptic inflammation.

Iron Status in Elite Soccer Players During the Sport Season

Introduction: The aim of the study was to investigate the changes of some indicators of iron status in elite soccer players throughout a competitive season. Methods: In the study participating 16 male professional soccer players. The measurements performed at the beginning of the season, after the re-building period, at the middle and at the end of the season. The indicators that measured were hematocrit, hemoglobin, serum iron and ferritin. Results: Hematocrit and serum iron decreased significantly during the season (p<0.05). Ferritn decreased after the re-building period (p<0.05) and then increased at the end of the season (p<0.05). Conclusion: Iron depletion is very common between elite soccer players and ferritin seems to be related to the training phase during the sport season.