Browsing by Author "Izquierdo, Mikel"
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- Effects of a modified backpack model on ground reaction forces in children of different ages during walking and runningPublication . Barbosa, João; Marques, Mário C.; Forte, Pedro; Santos, Catarina C.; Neiva, Henrique P.; Izquierdo, Mikel; Marinho, D.A.Backpacks are widely used by children to carry different objects and the literature supports that most backpacks contain excessive weight. To minimize the loading effects (i.e., ground reaction force), modified backpacks have been tested. However, the effects of elastics on shoulders straps are yet to be studied. Thus, the aim of this study was to test and compare the effect on the vertical ground reaction force of a standard backpack with a modified one with elastic straps while walking and running. Methods: 9 children (5 boys and 4 girls) were included in the group G-5 (age: 11.0 ± 0.3 years-old; body mass: 35.3 ± 7.3 kg; height: 1.41 ± 0.1 m) and twelve (7 boys and 5 girls) in G-9 (age: 15.0 ± 0.7 years-old; body mass: 56.7 ± 11.2 kg; height: 1.63 ± 0.1 m). Participants attended a single session and were initially asked to walk and then run over a force plate. The software Ergotest MuscleLab v8.0 (MuscleLab, Ergotest Innovation, Porsgrunn, Norway) was linked to the force platform and was used to collect and export data. The level of statistical significance was set at p ≤ 0.05. Additionally, the effect size of the differences verified on T-Tests was calculated based on Cohen’s d. Results: Statistically significant differences between a common backpack and a modified one with straps (p < 0.05) were observed for the variables time and force when walking. Regarding the running condition, the time variable did not differ significantly between the backpacks. However, the force variable changed considerably between backpack types (p < 0.05). The new straps minimized the forces magnitude, resulting in lower stress. Conclusions: The modified backpacks with shoulder elastic straps reduced the ground reaction force and impact when walking and running. The study may encourage other researchers to assess the effects of different movements (such as jumping or rotating) on ground reaction force.
- Effects of body fat and dominant somatotype on explosive strength and aerobic capacity trainability in prepubescent childrenPublication . Marta, Carlos; Marinho, D.A.; Barbosa, Tiago M.; Carneiro, André Luiz; Izquierdo, Mikel; Marques, Mário C.he purpose of this study was to analyze the influence of body fat and somatotype on explosive strength and aerobic capacity trainability in the prepubertal growth spurt, marked by rapid changes in body size, shape, and composition, all of which are sexually dimorphic. One hundred twenty-five healthy children (58 boys, 67 girls), aged 10–11 years (10.8 6 0.4 years), who were self-assessed in Tanner stages 1–2, were randomly assigned into 2 experimental groups to train twice a week for 8 weeks: strength training group (19 boys, 22 girls), endurance training group (21 boys, 24 girls), and a control group (18 boys, 21 girls). Evaluation of body fat was carried out using the method described by Slaughter. Somatotype was computed according to the Heath-Carter method. Increased endomorphy reduced the likelihood of vertical jump height improvement (odds ratio [OR], 0.10; 95% confidence interval [CI], 0.01–0.85), increased mesomorphy (OR, 6.15; 95% CI, 1.52–24.88) and ectomorphy (OR, 6.52; 95% CI, 1.71–24.91) increased the likelihood of sprint performance, and increased ectomorphy (OR, 3.84; 95% CI, 1.20–12.27) increased the likelihood of aerobic fitness gains. Sex did not affect the training-induced changes in strength or aerobic fitness. These data suggest that somatotype has an effect on explosive strength and aerobic capacity trainability, which should not be disregarded. The effect of adiposity on explosive strength, musculoskeletal magnitude on running speed, and relative linearity on running speed and aerobic capacity seem to be crucial factors related to training-induced gains in prepubescent boys and girls.
- The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power trainingPublication . Pereira, A.; Costa, Aldo M.; Leitão, José C.; Monteiro, A.M.; Izquierdo, Mikel; Silva, A.J.; Bastos, Estela; Marques, Mário C.Background:We studied the influence of the ACE I/D and ACTN3 R577X polymorphisms (single or combined) onlower-extremity function in older women in response to high-speed power training.Methods:One hundred and thirty-nine healthy older Caucasian women participated in this study (age: 65.5 ± 8.2 years,body mass: 67.0 ± 10.0 kg and height: 1.57 ± 0.06 m). Walking speed (S10) performance and functional capacityassessed by the“get-up and go”(GUG) mobility test were measured at baseline (T1) and after a consecutive 12-weekperiod of high-speed power training (40-75% of one repetition maximum in arm and leg extensor exercises; 3 sets4–12 reps, and two power exercises for upper and lower extremity). Genomic DNA was extracted from blood samples,and genotyping analyses were performed by PCR methods. Genotype distributions between groups were comparedby Chi-Square test and the gains in physical performance were analyzed by two-way, repeated-measures ANOVA.Results:There were no significant differences between genotype groups in men or women for adjusted baselinephenotypes (P > 0.05). ACE I/D and ACTN3 polymorphisms showed a significant interaction genotype-training only inS10 (P = 0.012 and P = 0.044, respectively) and not in the GUG test (P = 0.311 and P = 0.477, respectively). Analyses ofthe combined effects between genotypes showed no other significant differences in all phenotypes (P < 0.05) atbaseline. However, in response to high-speed power training, a significant interaction on walking speed (P = 0.048)was observed between the“power”(ACTN3 RR + RX & ACE DD) versus“non-power”muscularity-oriented genotypes(ACTN3 XX & ACE II + ID)].Conclusions:Thus, ACE I/D and ACTN3 R577X polymorphisms are likely candidates in the modulation ofexercise-related gait speed phenotype in older women but not a significant influence in mobility traits. The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power training. Available from: https://www.researchgate.net/publication/259244416_The_influence_of_ACE_ID_and_ACTN3_R577X_polymorphisms_on_lower-extremity_function_in_older_women_in_response_to_high-speed_power_training [accessed Nov 17, 2015].