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This study aimed to monitor the oxygenation and blood supply in three quadriceps muscles [the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF)] during squatting exercise to exhaustion. Eighteen young resistance-trained males performed five sets of 15 back squats in a Smith machine, with two warm-up sets [at 14% and 45% of the 15-repetition maximum (15RM)] and three main sets at 100% of the 15RM. Three near-infrared spectroscopy devices were attached to the VL, VM, and RF to record the muscle oxygen saturation (SmO2) and total hemoglobin (tHb, an index of muscle blood supply). The blood lactate concentration was measured after each set with a portable analyzer. The SmO2 and tHb data were analyzed by repeated-measures two-way ANOVA (muscle × set). Lactate data were analyzed by repeated-measures one-way ANOVA. The statistical significance was set at α = 0.05. The SmO2 dropped during each set (hitting zero in many instances) and was reinstated during recovery. The three main sets caused severe deoxygenation in the VL and VM, as opposed to moderate deoxygenation in the RF. From one set to the next, the initial value and the drop in the SmO2 increased, whereas the final SmO2 value decreased. The tHb increased in the VL, did not change considerably in the VM, and decreased in the RF during each set. The blood lactate concentration increased gradually from one set to the next, reaching about 10 mmol/L. These findings show pronounced differences in the physiological and metabolic responses of three quadriceps muscles to squatting exercise, thus highlighting the importance of studying such responses at multiple sites. [ABSTRACT FROM AUTHOR]

Many studies have highlighted the importance of physical activity in fostering health and preventing diseases among children and adolescents. Concurrently, mounting evidence underscores the detrimental health effects associated with high levels of sedentary behavior in children. Understanding the temporal changes in children's physical activity and sedentary behavior patterns is crucial for identifying evolving contexts that may require tailored interventions. This study investigates gender-specific changes in accelerometer-measured physical activity and sedentary behavior patterns among 8-11-year-old children from the same region of Greece, juxtaposing data from two different time frames (2014 and 2021). The cohort comprised 144 school-age children, with 68 participants from the 2014 cohort and 76 from the 2021 cohort. Physical activity and sedentary time were tracked using hip-worn accelerometers (Actigraph GT3X+). Participants were directed to wear the device continuously for seven consecutive days during their waking hours. Vector magnitude counts per minute and daily step counts were used to assess the total volume of physical activity, and Freedson population-specific cut-points for children were applied to classify physical activity levels. Factorial ANOVA models were conducted independently for each physical activity metric to explore discrepancies between the two measurement periods for each gender. The study's findings revealed a temporal trend indicating a decline in light physical activity alongside a significant increase in the percentage of total daily sedentary behavior. However, steps per day, counts per minute, and levels of moderate-to-vigorous physical activity remained relatively stable and did not significantly change. The average duration of sedentary bouts significantly increased only among girls. The results also indicated a slight increase from 2014 to 2021 regarding the proportion of children meeting physical activity recommendations. Modern children allocate less time to light physical activity and more time to sedentary pursuits, significantly increasing uninterrupted sedentary periods during the day. Our results underscore the need for tailored initiatives to promote and enable physical activity, particularly among girls. Addressing barriers and fostering inclusive opportunities is imperative to empower all children to adopt active and healthy lifestyles. [ABSTRACT FROM AUTHOR]

Purpose: To examine the recovery kinetics of exercise-induced muscle damage (EIMD), neuromuscular fatigue, and performance following small-sided games (SSGs) of different densities in soccer. Methods: Ten male players randomly completed 3 trials: a control trial (no SSGs), 4v4 SSGs (62.5 m2/player), and 8v8 SSGs (284.4 m2/player). External and internal load were monitored using GPS technology, heart-rate monitors, and rating of perceived exertion. Delayed-onset muscle soreness (DOMS), creatine kinase (CK), isokinetic strength, countermovement jump (CMJ), and sprint were determined at baseline, as well as at 24, 48, and 72 hours post-SSGs. Neuromuscular fatigue was assessed at baseline and at 1, 2, and 3 hours post-SSGs. Results: DOMS increased (P <.05) in 4v4 for 72 hours and in 8v8 for 24 hours with that of knee flexors being more pronounced than that of extensors. CK increased (P <.05) in 4v4 for 72 hours and in 8v8 for 24 hours. Neuromuscular fatigue increased (P <.05) in 4v4 for 2 hours and in 8v8 for 3 hours. Strength declined (P <.05) in 4v4 for 48 hours and in 8v8 for 72 hours. CMJ decreased (P <.05) in 4v4 for 24 hours and in 8v8 for 48 hours. Sprint decreased (P <.05) for 48 hours in 4v4 and for 72 hours in 8v8. Conclusions: SSGs are associated with a prolonged rise of EIMD and induce short-term neuromuscular fatigue and slow recovery kinetics of strength, jump, and sprinting performance. The time for complete recovery is longer for SSGs of lower density. [ABSTRACT FROM AUTHOR]

Purpose: To determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. Methods: Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72 h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3 h posttraining. Results: Fatigue increased (P <.05) in SEPT/1:5 (∼4–30%) for 3 h and in SEPT/1:8 (∼8–17%) for 2 h. Strength performance declined (P <.05) in both SEPT trials (∼5–20%) for 48 h. Speed decreased (∼4–18%; P <.05) for 72 h in SEPT/1:5 and for 48 h in SEPT/1:8. Countermovement-jump performance decreased (∼7–12%; P <.05) in both SEPT trials for 24 h. DOMS increased (P <.05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48 h. Creatine kinase increased (∼1- to 2-fold, P <.05) in both SEPT trials for 72 h. Conclusions: SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48 h), speed (72 h), and jump performance (24 h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics. [ABSTRACT FROM AUTHOR]

Although normative data for physical fitness parameters are available at International and European level, contemporary normative scores from North-East Greece are sparse. Moreover, direct comparison of physical fitness data to European norms is still absent. Objective. This investigation aimed to evaluate the cardiorespiratory and musculoskeletal fitness of Greek preadolescents from North-East Greece in comparison to current European reference norms. Method. 300 pre-adolescent (mean Tanner stage A: 1.67 ± 0.6; mean Tanner stage B: 1.65 ± 0.6) boys and girls (mean age: 9.4 ± 1.1 years) completed a testing battery of 20-m shuttle run test (20m SRT), handgrip strength, and standing broad jump. Scores for each testing parameter were compared against European age- and sex-specific centiles and then grouped into quintiles. Results. For all testing parameters, 60-81% of participants were classified as having physical fitness performance scores of "moderate" or lower level. No differences were noted between boys and girls. Data corroborated that physical fitness levels of Greek preadolescent boys and girls are among the lowest recorded in the European region. Conclusion. This data suggest that physical fitness levels of pre-adolescents in North East Greece may be suboptimal, which strongly indicates the need for adopting large-scale fitness assessments in this particular region. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of a complex, short-term strength/power training protocol on performance and body composition of elite early adolescent soccer players. Methods: Twenty-two players (14-15 y) were randomly assigned to (1) an experimental group (N = 12; participated in a 5-wk training protocol with traditional multijoint power resistance exercises, Olympic-style lifts, plyometric drills, and speed work; 4 times per week) or (2) a control group (N = 10). Strength and power performance (jumping, speed, change of direction, repeated sprint ability, endurance, isokinetic strength of knee flexors and extensors, maximal strength in various lifts, and speed-endurance) were evaluated pretraining and posttraining. Results: Cessation of training for 5 weeks in the control group induced amarked performance deterioration (-5%-20%). Training not only prevented strength performance deterioration but also increased it (-2%-30%). Endurance and repeated sprint ability declined to a smaller extent in experimental group compared with control group (15% vs 7.5%). Isometric strength and body composition remained unaltered in both groups. Conclusions: Results demonstrate that (1) young players exhibit a high level of trainability of their strength/power performance (but not endurance) in response to a short-term complex training protocol during early adolescence, (2) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective, (3) lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors, (4) cessation of training for only 5 weeks results in marked deterioration of strength/power and endurance performance, and (5) improvement of strength/power performance may be related to neural-based adaptation as body composition remained unaffected. [ABSTRACT FROM AUTHOR]

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): 32?8-3286, 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 x 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. KEY WORDS free radicals, antioxidant status, soccer, exercise-induced inflammation, muscle soreness

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. Key Words plyometric exercise, muscle soreness, stress hormones, strength