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  • Author: Mikel Izquierdo x
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Óscar Martínez de Quel, Ignacio Ara, Mikel Izquierdo and Carlos Ayán

Objective: To assess the discriminative ability of several fitness dimensions and anthropometric attributes for forecasting competitive success in female karate athletes. Methods: Fitness and anthropometric data from 98 female junior karatekas obtained during the training camps of the Spanish National Karate Federation between 1999 and 2012 were used. Binary logistic-regression models were built to ascertain whether the set of fitness and anthropometric variables could predict future sporting-performance levels. For this purpose, participants were classified as elite (medalist in World or European Championships in the senior category) or subelite (at least a medalist in Spanish National Championships in cadet or junior but not included in the elite group), according to the results achieved up to 2019. Results: Participants who were subsequently classified as elite karatekas showed significant differences in agility, upper- and lower-body muscle power, and general fitness in comparison with those who were classified as subelite in the senior category. A total of 57 junior female karatekas who were subsequently classified as elite (7) or subelite (50) were included in the binary logistic-regression analysis. Resultant models showed significant capacity to predict karate performance. Conclusions: Assessing physical fitness in junior categories can be a useful resource to determine future karate success. Coaches in this sport should pay special attention to the levels of muscle power and agility shown by their athletes, as both fitness dimensions could be indicators of future sportive success.

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Iker Leoz-Abaurrea, Mikel Izquierdo, Miriam Gonzalez-Izal and Roberto Aguado-Jiménez

The efficacy of the use of an upper body compression garment (UBCG) as an ergogenic aid to reduce thermoregulatory strain in older adults remains unknown. The aim of this study was to evaluate the effects of UBCG on thermoregulatory, cardiorespiratory, and perceptual responses during cycling in a temperate environment (~25 °C, 66% rh) in trained older adults. Twelve cyclists aged 66 ± 2 years performed an intermittent 1-hr cycling trial at 50% of the peak power output followed by 10 min of passive recovery. Participants were provided with either commercially available UBCG or a control garment in a randomized order. UBCG increased thermoregulatory strain during exercise, as indicated by a significantly higher core temperature (38.1 ± 0.3 °C vs. 37.9 ± 0.3 °C; p = .04), body temperature (36.9 ± 0.2 °C vs. 36.7 ± 0.2 °C; p = .01), and thermal sensation (8.0 ± 0.4 vs. 7.5 ± 1.0; p = .02). These results suggest that the use of UBCG in trained older adults does not reduce the thermoregulatory strain during moderate exercise.

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Eduardo Lusa Cadore, Miriam González-Izal, Rafael Grazioli, Igor Setuain, Ronei Silveira Pinto and Mikel Izquierdo

Purpose: To compare the concentric and eccentric training effects on fatigue induced by eccentric and concentric protocols. Methods: A total of 22 men and women (22 [3.6] y) were assigned to concentric (GCON, n = 11) or eccentric training (GECC, n = 11). The concentric (CON) and eccentric (ECC) protocols were composed of 4 sets of 20 knee-extension/flexion repetitions. Force losses were analyzed by comparing 10 repetitions’ mean torques during the protocols and by verifying the maximal voluntary contraction and rate of torque development before and after the protocols. Muscle damage was assessed using echo intensity of the vastus lateralis 48 h after the protocols. Training consisted of 6 wk of isokinetic exercise at 60°/s (concentric or eccentric) twice weekly. Results: Before training, both protocols resulted in dynamic and isometric force losses in GCON and GECC (P < .01), but the magnitude was greater after the CON protocol than after the ECC protocol (P < .001). After training, both GCON and GECC showed similar force decreases during the CON and ECC protocols (P < .01), and these changes were not different from the pretraining decreases. Regarding maximal voluntary contraction after training, GECC showed lower force decreases than GCON after ECC exercise (−13.7% vs −22.3%, respectively, P < .05), whereas GCON showed lower maximal voluntary contraction decreases after CON exercise compared with pretraining (−29.2%, P < .05). Losses in rate of torque development were similar after the protocols before and after the training regimens. No changes in echo intensity were observed after the protocols before and after training. Conclusion: Both interventions resulted in similar force decreases during fatigue protocols compared with those associated with pretraining.

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Pedro Lopez, Mikel Izquierdo, Regis Radaelli, Graciele Sbruzzi, Rafael Grazioli, Ronei Silveira Pinto and Eduardo Lusa Cadore

In this meta-analysis, we investigated the effect of resistance training (RT) alone or included in a multimodal training on physical frailty outcomes, and whether different variables of RT prescription affect these outcomes. We identified 15 relevant studies searching through MEDLINE, Cochrane Central Register of Controlled Trials, SPORTDiscus, and PEDro database. Postintervention standardized mean difference scores were computed and combined using fixed effects meta-analysis. Analyses have shown positive effects of interventions on maximum strength, gait speed, and Timed Up and Go test. Further analyses have shown significant greater effect of shorter periods on maximum strength. Regarding RT prescription, percentage of one-repetition maximum showed significant effect on physical variables, whereas RT based on rate of perceived effort presented lower effect in the Timed Up and Go test. Although multimodal training is an effective intervention to increase physical capacity, caution should be taken regarding the period and the method to control RT intensity to optimize enhancements in frail older people.

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Igor Setuain, Mikel Izquierdo, Fernando Idoate, Eder Bikandi, Esteban M. Gorostiaga, Per Aagaard, Eduardo L. Cadore and Jesús Alfaro-Adrián


The muscular function restoration related to the type of physical rehabilitation followed after anterior cruciate ligament reconstruction (ACLR) using autologous hamstring tendon graft in terms of strength and cross-sectional area (CSA) remain controversial.


To analyze the CSA and force output of quadriceps and hamstring muscles in subjects following either an Objective Criteria-Based Rehabilitation (OCBR) algorithm or the usual care (UCR) for ACL rehabilitation in Spain, before and 1 year after undergoing an ACLR.


Longitudinal clinical double-blinded randomized controlled trial.


Sports-medicine research center.


40 recreational athletes (30 male, 10 female [24 ± 6.9 y, 176.55 ± 6.6 cm, 73.58 ± 12.3 kg]).


Both groups conducted differentiated rehabilitation procedures after ACLR. Those belonging to OCBR group were guided in their recovery according to the current evidence-based principles. UCR group followed the national conventional approach for ACL rehabilitation.

Main Outcome Measures:

Concentric isokinetic knee joint flexor-extension torque assessments at 180°/s and Magnetic Resonance Imaging (MRI) evaluations were performed before and 12 months after ACLR. Anatomical muscle CSA (mm2) was assessed, in Quadriceps, Biceps femoris, Semitendinous, Semimembranosus, and Gracilis muscles at 50% and 70% femur length.


Reduced muscle CSA was observed in both treatment groups for Semitendinosus and Gracilis 1 year after ACLR. At 1-year follow-up, subjects allocated to the OCBR demonstrated greater knee flexor and extensor peak torque values in their reconstructed limbs in comparison with patients treated by UCR.


Objective atrophy of Semitendinosus and Gracilis muscles related to surgical ACLR was found to persist in both rehabilitation groups. However, OCBR after ACLR lead to substantial gains on maximal knee flexor strength and ensured more symmetrical anterior-posterior laxity levels at the knee joint.

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Keijo Häkkinen, Markku Alen, Mauri Kallinen, Mikel Izquierdo, Kirsi Jokelainen, Helka Lassila, Esko Mälkiä, William J. Kraemer and Robert U. Newton

Forty-two healthy men and women in two age groups (40 and 70 years) were examined for muscle cross-sectional area (CSA), maximal voluntary bilateral isometric force, force-time characteristics, maximal concentric 1 RM. and power performance of the leg extensors in a sitting position, squat jump, and standing long-jump. The results suggested that the decline in maximal strength with increasing age is related to the decline in muscle CSA; however, particularly in older women, the force/CSA ratio may also be lowered. Explosive force seems to decrease with increasing age even more than maximal strength. suggesting that muscle atrophy with aging is greater in fast-twitch fibers. The voluntary activation of the agonist and antagonist muscles seems to vary depending on the type of muscle action and/or velocity and time duration of the action in both age groups but to a greater extent in older people. There appears to be an age-related increase in antagonist co activation. especially in dynamic explosive movements.

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Carlos Marta, Ana R. Alves, Pedro T. Esteves, Natalina Casanova, Daniel Marinho, Henrique P. Neiva, Roberto Aguado-Jimenez, Alicia M. Alonso-Martínez, Mikel Izquierdo and Mário C. Marques

Purpose: The aim of this study was to determine the effects of an 8-week program of resistance training (RT) or suspension training (ST) on explosive strength in prepubescent boys. Methods: Fifty-seven boys aged 10–11 years were assigned to 2 training groups, RT or ST or a control group (no training program). Boys trained twice weekly for 8 weeks. Results: A significant interaction was reported with a large (P < .001, ηp2=.463), medium (P < .001, ηp2=.395), and small effect sized (P ≤ .001, ηp2=.218) in the 1-kg ball throw, 3-kg ball throw, and time-at-20-m test, respectively. There was no significant interaction in the countermovement vertical jump or the standing long jump. Changes from preintervention to postintervention for the 1-kg ball throw were 5.94% and 5.82% for the ST and RT, respectively, and 8.82% and 8.14% in the 3-kg ball throw for the ST and RT, respectively. The improvement in the 20-m sprint was 1.19% for the ST and 2.33% for the RT. Conclusion: Traditional RT and ST seem to be effective methods for improving explosive strength in prepubescent boys. ST could be considered as an alternative modality to optimize explosive strength training in school-based programs.

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Rodrigo Ramírez-Campillo, Cristian Martínez, Carlos I. de La Fuente, Eduardo L. Cadore, Mário C. Marques, Fabio Y. Nakamura, Irineu Loturco, Alexis Caniuqueo, Rodrigo Cañas and Mikel Izquierdo

Older women participated in a 12-week high-speed resistance training program under two supervisor-to-subject ratio methods (i.e., high versus low supervision) to assess its effects on muscle strength, power, functional performance, and quality of life assessed before (T1) and after (T2) intervention. Women were divided into either the control group (CG, n = 15), high supervision group (HSG, n = 30), or low supervision group (LSG, n = 28). The training program included exercises requiring high-speed concentric muscle actions. No differences were observed among groups at T1. Between T1 and T2, the HSG showed a higher (p < .05) improvement in muscle strength (ES = 0.36–1.26), power (ES = 0.5–0.88), functional performance (ES = 0.52–0.78), and quality of life (ES = 0.44–0.82) compared with LSG and CG. High-speed resistance training under closer supervision is more effective for improving muscle strength, power, functional performance, and quality of life in older women.