Iron status markers are only transiently affected by a football game.

We examined the temporal variation of iron's status markers during a 60 h period following a football game. Thirty-four male football players were randomly assigned to a control group (CG, N = 14, participated only in measurements and training) or an experimental group (EG, N = 20, took part in a football game one week after the completion of the competitive season). All participants trained regularly for two consecutive days after the game. Training and game load was monitored with high time-resolution global positioning system (GPS) devices. Blood samples were collected and muscle damage markers and repeated sprint ability (RSA) were assessed pre-game and at 2 h, 12 h 36 h and 60 h post-game. No changes were noted in CG. Iron concentration decreased (P < 0.05) 2 h post-game and normalised thereafter whereas total iron binding capacity increased (P < 0.05) 12-60 h of recovery (P < 0.05). Erythrocytes, haemoglobin (HGB) concentration, plasma volume, haematocrit, mean cell volume, mean cell HGB, mean cell HGB concentration, red cell width-SD, red cell width-CV, ferritin concentration and transferrin saturation remained unaltered during the intervention period. Creatine kinase activity and muscle soreness increased (P < 0.05) throughout recovery in EG. RSA declined (P < 0.05) until 36 h of recovery and normalised thereafter. Our data demonstrate that iron status markers are only transiently affected by a football game.

The time-frame of acute resistance exercise effects on football skill performance: the impact of exercise intensity.

The purpose of this study was to determine the recovery rate of football skill performance following resistance exercise of moderate or high intensity. Ten elite football players participated in three different trials: control, low-intensity resistance exercise (4 sets, 8-10 repetitions/set, 65-70% 1 repetition maximum [1RM]) and high-intensity resistance exercise (4 sets, 4-6 repetitions/set, 85-90% 1RM) in a counterbalanced manner. In each experimental condition, participants were evaluated pre, post, and at 24, 48, 72 h post exercise time points. Football skill performance was assessed through the Loughborough Soccer Passing Test, long passing, dribbling, shooting and heading. Delayed onset muscle soreness, knee joint range of motion, and muscle strength (1RM) in squat were considered as muscle damage markers. Blood samples analysed for creatine kinase activity, C-reactive protein, and leukocyte count. Passing and shooting performance declined (P < 0.05) post-exercise following resistance exercise. Strength declined post-exercise following high-intensity resistance exercise. Both trials induced only a mild muscle damage and inflammatory response in an intensity-dependent manner. These results indicate that football skill performance is minimally affected by acute resistance exercise independent of intensity suggesting that elite players may be able to participate in a football practice or match after only 24 h following a strength training session.

Plyometrics' trainability in preadolescent soccer athletes.

Plyometric training (PT) is a widely used method to improve muscle ability to generate explosive power. This study aimed to determine whether preadolescent boys exhibit plyometric trainability or not. Forty-five children were randomly assigned to either a control (CG, N = 21, 10.6 ± 0.5 years; participated only in regular soccer practice) or a plyometric training group (PTG, N = 24, 10.6 ± 0.6 years; participated in regular soccer practice plus a plyometric exercise protocol). Both groups trained for 12 weeks during the in-season period. The PT exercises (forward hopping, lateral hopping, shuffles, skipping, ladder drills, skipping, box jumps, low-intensity depth jumps) were performed twice a week. Preadolescence was verified by measuring Tanner stages, bone age, and serum testosterone. Speed (0-10, 10-20, 20-30 m), leg muscle power (static jumping, countermovement jumping, depth jumping [DJ], standing long jump [SLJ], multiple 5-bound hopping [MB5]), leg strength (10 repetition maximum), anaerobic power (Wingate testing), and soccer-specific performance (agility, kicking distance) were measured at baseline, midtraining, and posttraining. The CG caused only a modest (1.2-1.8%) increase in speed posttraining. The PTG induced a marked (p < 0.05) improvement in all speed tests (1.9-3.1% at midtraining and 3-5% at posttraining) and vertical jump tests (10-18.5% at midtraining and 16-23% at posttraining), SLJ (2.6% at midtraining and 4.2% at posttraining), MB5 (14.6% at midtraining and 23% at posttraining), leg strength (15% at midtraining and 28% at posttraining), agility (5% at midtraining and 23% at posttraining), and kicking distance (13.6% at midtraining and 22.5% at posttraining). Anaerobic power remained unaffected in both groups. These data indicate that (a) prepubertal boys exhibit considerable plyometric trainability, and (b) when soccer practice is supplemented with a PT protocol, it leads to greater performance gains.

Physiological and performance adaptations of elite Greco-Roman wrestlers during a one-day tournament.

The aim of this study was to determine the effects of a simulated one-day Greco-Roman wrestling tournament on selected performance and inflammatory status indices. Twelve competitive wrestlers (22.1 ± 1.3 years) completed five matches according to the official Olympic wrestling tournament regulations following a ~6% weight loss. Performance measurements, muscle damage assessment, and blood sampling were performed before and following each match. Performance and inflammatory markers were not affected by weight loss. Mean wrestling heart rate reached ~85% of maximal and lactate concentration exceeded 17 mM. Fatigue rating demonstrated a progressive rise (P < 0.05) throughout the tournament, peaking in match 4. Performance demonstrated a progressive deterioration (P < 0.05) throughout the tournament, especially in the last two matches (P < 0.05), with upper-body measures exhibiting a greater decline (P < 0.05) and remaining below baseline (P < 0.05) until the end of the tournament. Muscle damage markers increased during the course of the tournament with upper limbs affected more. Creatine kinase activity, CRP levels, IL-6 concentration, and leukocyte counts increased (P < 0.05) progressively throughout the tournament, peaking in the last two matches. Cortisol, epinephrine and norepinephrine increased (P < 0.05) after each match, but testosterone declined (P < 0.05) progressively, reaching a nadir before the last match. This inflammatory response was accompanied by a marked increase (p < 0.05) in lipid peroxidation, protein oxidation, and antioxidant status markers indicating the development of oxidative stress. These results suggest that a one-day wrestling tournament may induce significant physiological demands on wrestlers that may adversely affect their performance and inflammatory status especially during the later stages of the tournament.

Time-course of changes in oxidative stress and antioxidant status responses following a soccer game.

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.

Time-course of changes in inflammatory and performance responses following a soccer game.

OBJECTIVE: : To study the effects of a single soccer game on indices of performance, muscle damage, and inflammation during a 6-day recovery period. DESIGN: : Participants were assigned to either an experimental group (E, played in the game; n = 14) or a control group (C, did not participate in the game; n = 10). SETTING: : Data were collected on a soccer field and at the Physical Education and Sports Science laboratory of the Democritus University of Thrace before and after the soccer game. PARTICIPANTS: : Twenty-four elite male soccer players (age, 20.1 +/- 0.8 years; height, 1.78 +/- 0.08 m; weight, 75.2 +/- 6.8 kg). MAIN OUTCOME MEASUREMENTS: : Muscle strength, vertical jumping, speed, DOMS, muscle swelling, leukocyte count, creatine kinase (CK), lactate dehydrogenase (LDH), C-reactive protein (CRP), cortisol, testosterone, cytokines IL-6 and IL-1b, thioburbituric acid-reactive substances (TBARS), protein carbnyls (PC), and uric acid (UA). RESULTS: : Performance deteriorated 1 to 4 days post-game. An acute-phase inflammatory response consisted of a post-game peak of leukocyte count, cytokines, and cortisol, a 24-hour peak of CRP, TBARS, and DOMS, a 48-hour peak of CK, LDH, and PC, and a 72-hour peak of uric acid. CONCLUSION: : A single soccer game induces short-term muscle damage and marked but transient inflammatory responses. Anaerobic performance seems to deteriorate for as long as 72-hour post-game. The acute phase inflammatory response in soccer appears to follow the same pattern as in other forms of exercise. These results clearly indicate the need of sufficient recovery for elite soccer players after a game.

Oxidative stress biomarkers responses to physical overtraining: implications for diagnosis.

Overtraining syndrome is characterized by declining performance and transient inflammation following periods of severe training with major health implications for the athletes. Currently, there is no single diagnostic marker for overtraining. The present investigation examined the responses of oxidative stress biomarkers to a resistance training protocol of progressively increased and decreased volume/intensity. Twelve males (21.3+/-2.3 years) participated in a 12-week resistance training consisting of five 3-week periods (T1, 2 tones/week; T2, 8 tones/week; T3, 14 tones/week; T4, 2 tones/week), followed by a 3-week period of complete rest. Blood/urine samples were collected at baseline and 96 h following the last training session of each period. Performance (strength, power, jumping ability) increased after T2 and declined thereafter, indicating an overtraining response. Overtraining (T3) induced sustained leukocytosis, an increase of urinary isoprostanes (7-fold), TBARS (56%), protein carbonyls (73%), catalase (96%), glutathione peroxidase, and oxidized glutathione (GSSG) (25%) and a decline of reduced glutathione (GSH) (31%), GSH/GSSG (56%), and total antioxidant capacity. Isoprostanes and GSH/GSSG were highly (r=0.764-0.911) correlated with performance drop and training volume increase. In conclusion, overtraining induces a marked response of oxidative stress biomarkers which, in some cases, was proportional to training load, suggesting that they may serve as a tool for overtraining diagnosis.

Dose-related effects of prolonged NaHCO3 ingestion during high-intensity exercise.

PURPOSE: Sodium bicarbonate (NaHCO3) ingestion may prevent exercise-induced perturbations in acid-base balance, thus resulting in performance enhancement. This study aimed to determine whether different levels of NaHCO3 intake influences acid-base balance and performance during high-intensity exercise after 5 d of supplementation. METHODS: Twenty-four men (22 +/- 1.7 yr) were randomly assigned to one of three groups (eight subjects per group): control (C, placebo), moderate NaHCO3 intake (MI, 0.3 g x kg(-1) x d(-1)), and high NaHCO3 intake (HI, 0.5 g x kg(-1) x d(-1)). Arterial pH, HCO3(-), PO2, PCO2, K+, Na, base excess (BE), lactate, and mean power (MP) were measured before and after a Wingate test pre- and postsupplementation. RESULTS: HCO3(-) increased proportionately to the dosage level. No differences were detected in C. Supplementation increased MP (W x kg(-)) in MI (7.36 +/- 0.7 vs 6.73 +/- 1.0) and HI (7.72 +/- 0.9 vs 6.69 +/- 0.6), with HI being more effective than MI. NaHCO3 ingestion resulted postexercise in increased lactate (mmol x L(-1)) (12.3 +/- 1.8 vs 10.3 +/- 1.9 and 12.4 +/- 1.2 vs 10.4 +/- 1.5 in MI and HI, respectively), reduced exercise-induced drop of pH (7.305 +/- 0.04 vs 7.198 +/- 0.02 and 7.343 +/- 0.05 vs 7.2 +/- 0.01 in MI and HI, respectively) and HCO3(-) (mmol x L(-1)) (13.1 +/- 2.4 vs 17.5 +/- 2.8 and 13.2 +/- 2.7 vs 19.8 +/- 3.2 for HCO3 in MI and HI, respectively), and reduced K (3.875 +/- 0.2 vs 3.625 +/- 0.3 mmol x L(-1) in MI and HI, respectively). CONCLUSION: NaHCO3 administration for 5 d may prevent acid-base balance disturbances and improve performance during anaerobic exercise in a dose-dependent manner.

Recovery kinetics of knee flexor and extensor strength after a football match.

We examined the temporal changes of isokinetic strength performance of knee flexor (KF) and extensor (KE) strength after a football match. Players were randomly assigned to a control (N = 14, participated only in measurements and practices) or an experimental group (N = 20, participated also in a football match). Participants trained daily during the two days after the match. Match and training overload was monitored with GPS devices. Venous blood was sampled and muscle damage was assessed pre-match, post-match and at 12 h, 36 h and 60 h post-match. Isometric strength as well as eccentric and concentric peak torque of knee flexors and extensors in both limbs (dominant and non-dominant) were measured on an isokinetic dynamometer at baseline and at 12 h, 36 h and 60 h after the match. Functional (KFecc/KEcon) and conventional (KFcon/KEcon) ratios were then calculated. Only eccentric peak torque of knee flexors declined at 60 h after the match in the control group. In the experimental group: a) isometric strength of knee extensors and knee flexors declined (P<0.05) at 12 h (both limbs) and 36 h (dominant limb only), b) eccentric and concentric peak torque of knee extensors and flexors declined (P<0.05) in both limbs for 36 h at 60°/s and for 60 h at 180°/s with eccentric peak torque of knee flexors demonstrating a greater (P<0.05) reduction than concentric peak torque, c) strength deterioration was greater (P<0.05) at 180°/s and in dominant limb, d) the functional ratio was more sensitive to match-induced fatigue demonstrating a more prolonged decline. Discriminant and regression analysis revealed that strength deterioration and recovery may be related to the amount of eccentric actions performed during the match and athletes' football-specific conditioning. Our data suggest that recovery kinetics of knee flexor and extensor strength after a football match demonstrate strength, limb and velocity specificity and may depend on match physical overload and players' physical conditioning level.

Oxidative stress and inflammatory responses following an acute bout of isokinetic exercise in obese women with knee osteoarthritis.

BACKGROUND: Obesity is associated with osteoarthritis and it is accompanied by chronic inflammation and elevated oxidative stress. Strengthening-type exercise is used in knee osteoarthritis (KOA) rehabilitation. This study determined how acute isokinetic exercise influences inflammatory responses of obese middle-aged women with KOA. METHODS: Ten obese women with KOA and 10 age/weight-matched controls performed an isokinetic exercise protocol. Assessment of performance (knee extensor/flexor torque), muscle soreness (DOMS), knee flexibility (KJRM), and pain, and blood collection were performed pre-exercise, post-exercise, and at 24h post-exercise. Blood was analyzed for creatine kinase activity (CK), lactate dehydrogenase activity (LDH), CRP, leukocytes, uric acid, IL-6, TBARS, lipid hydroperoxides (LPX), protein carbonyls (PC), oxidized (GSH) and reduced glutathione (GSSG), total antioxidant capacity (TAC), catalase activity, and glutathione peroxidase activity (GPX). RESULTS: Physical function remained unaltered by exercise (only torque at 90°/s decreased at 24h). Exercise increased DOMS throughout recovery but KJRM and pain remained unchanged. CK, LDH, and uric acid increased similarly in both groups. CRP remained unaffected by exercise while IL-6 increased only post-exercise. TBARS, PC, LPH, GSSG, and TAC increased only post-exercise in both groups. GSH and GSH/GSSG declined post-exercise and normalized thereafter. Catalase and GPX increased only in patients post-exercise. CONCLUSION: Isokinetic exercise induces only a mild inflammatory response of very short duration (<24h) without affecting physical function and pain in KOA patients suggesting that moderate strengthening-type exercise may be safe for this patient cohort. These results indicate that KOA patients may be able to receive another exercise stimulus after only 48h. CLINICAL RELEVANCE: Isokinetic exercise produces minimal inflammation and pain in knee osteoarthritis patients, could be performed every 48h during rehabilitation, and up-regulates patients' antioxidant system.

Cell-free plasma DNA as a novel marker of aseptic inflammation severity related to exercise overtraining.

BACKGROUND: Circulating free plasma DNA is implicated in conditions associated with tissue injury, including exercise-induced inflammation, and thus is a potential marker for athletic overtraining. METHODS: We measured free plasma DNA along with C-reactive protein (CRP), creatine kinase (CK), and uric acid (UA) in 17 recreationally trained men participating in a 12-week resistance training regimen (8 resistance multi-joint exercises selected to stress the entire musculature: bench press, squat, leg press, snatch, hang clean, dead lifts, barbell arm curls, and rowing), consisting of 4 training periods (t1, t2, t3, and t4). RESULTS: Plasma DNA concentrations increased markedly after t1, t2, and t3 and returned to baseline after t4. There were substantial differences between t2 and t1 and between t3 and t2 plasma DNA concentrations. CRP increased by 300% after t2 and by 400% after t3 (there was no difference between t2 and t3 CRP values) compared with baseline (t0). CK increased only after t3. UA increased after t2 and t3, with a greater increase after t3. CONCLUSIONS: This study demonstrates that, after chronic excessive resistance exercise, plasma DNA concentrations increase in proportion to training load, suggesting that plasma DNA may be a sensitive marker for overtraining-induced inflammation.