Childhood obesity is increasing alarmingly, and a strong association with chronic diseases has been established. Specific adipokines are released from the adipose tissue and relate with chronic diseases even in the pediatric population. Adiponectin levels are lower in obesity and increase with decreasing body weight. A few pediatric studies examining a possible relationship between resistin and obesity do not provide a clear picture. Most studies agree that visfatin levels appear elevated in childhood obesity. Exercise seems to increase adiponectin levels whereas resistin levels are reduced. The lack of data on the effects of acute and chronic exercise on visfatin levels precludes us from making safe conclusions as to what the effects of exercise (acute or chronic) would be on visfatin levels in children. Clearly, exercise has an impact on the adipose tissue and the release of adiponectin, resistin, and visfatin. However, other factors affect the secretion rate of these adipokines from the adipose tissue; these factors should also be taken into consideration when examining the effects of exercise on adipokines. Gender, age, body composition, physical activity levels, mode and intensity of exercise are some of the factors that should be looked into in future studies.
Athanasios Z. Jamurtas, Antonios Stavropoulos-Kalinoglou, Stilianos Koutsias, Yiannis Koutedakis and Ioannis Fatouros
Chariklia K. Deli, Ioannis G. Fatouros, Vassilis Paschalis, Kalliopi Georgakouli, Athanasios Zalavras, Alexandra Avloniti, Yiannis Koutedakis and Athanasios Z. Jamurtas
Research regarding exercise-induced muscle-damage mainly focuses on adults. The present study examined exercise-induced muscle-damage responses in adults compared with children.
Eleven healthy boys (10–12 y) and 15 healthy men (18–45 y) performed 5 sets of 15 maximal eccentric contractions of the knee extensors. Range of motion (ROM), delayed onset muscle soreness (DOMS) during squat and walking, and peak isometric, concentric and eccentric torque were assessed before, post, 24, 48, 72, and 96 hr postexercise. Creatine kinase (CK) activity was assessed before and 72 hr postexercise.
Eccentric exercise resulted in DOMS during squat that persisted for up to 96h in men, and 48 hr in boys (p < .05), and DOMS during walking that persisted for up to 72 hr in men, and 48 hr in boys (p < .01). The ROM was lower in both age groups 48 hr postexercise (p < .001). Isometric (p < .001), concentric (p < .01) and eccentric (p < .01) force decreased post, and up to 48 hr postexercise in men. Except for a reduction in isometric force immediately after exercise, no other changes occurred in boys’ isokinetic force. CK activity increased in men at 72 hr postexercise compared with pre exercise levels (p = .05).
Our data provide further confirmation that children are less susceptible to exercise-induced muscle damage compared with adults.
Theofanis Tzatzakis, Konstantinos Papanikolaou, Dimitrios Draganidis, Panagiotis Tsimeas, Savvas Kritikos, Athanasios Poulios, Vasiliki C. Laschou, Chariklia K. Deli, Athanasios Chatzinikolaou, Alexios Batrakoulis, Georgios Basdekis, Magni Mohr, Peter Krustrup, Athanasios Z. Jamurtas and Ioannis G. Fatouros
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.
Sofia Aggeloussi, Anastasios A. Theodorou, Vassilis Paschalis, Michalis G. Nikolaidis, Ioannis G. Fatouros, Emmanuel O. Owolabi, Dimitris Kouretas, Yiannis Koutedakis and Athanasios Z. Jamurtas
To investigate the effects of obesity and exercise training on plasma adipocytokines a sample of 42 children (lean = 24, %BF = 17.8 ± 7.5%; obese = 18; %BF = 29.1 ± 9.3%; mean age = 12.4 ± 1.9 yrs), were divided into 4 age-matched for activity groups: lean inactive (n = 11), obese inactive (n = 9), lean active (n = 13) and obese active (n = 9). Active children participated in swimming training (≥1 year, ≥3 times/week, ≥1 h per session, covering a distance of 10,000−12,000 m per week). Obese individuals demonstrated greater visfatin levels (3.3 ± 1.3 ng/ml) than their lean counterparts (2.6 ± 1.1 ng/ml; p = .06) whereas adiponectin was significantly lower in obese children (3.8 ± 1.9) than their lean counterparts (5.9 ± 2.7; p £ .05). Insulin and HOMA values were significantly greater in obese compared with lean children (p £ .05). Within obese individuals, active individuals had significantly lower visfatin levels (2.8 ± 1.2 ng/ml) compared with their inactive counterparts (3.8 ± 1.2 ng/ml; p £ .05). Resistin levels were comparable between groups (p > .05). Childhood obesity elevates visfatin and lowers adiponectin levels whereas exercise training could reduce visfatin levels in obese children.
Athanasios Chatzinikolaou, Konstantinos Michaloglou, Alexandra Avloniti, Diamanda Leontsini, Chariklia K. Deli, Dimitris Vlachopoulos, Luis Gracia-Marco, Sotirios Arsenis, Ioannis Athanailidis, Dimitrios Draganidis, Athanasios Z. Jamurtas, Craig A. Williams and Ioannis G. Fatouros
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 a marked 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.