Browsing by Author "Jerez-Mayorga, Daniel"

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    Age-dependent Knee Joint Isokinetic Profile in Professional Male Soccer Players
    Torres-Banduc, Maximiliano A.; Jerez-Mayorga, Daniel; Huerta Ojeda, Álvaro; Bishop, Chris; Ramirez-Campillo, Rodrigo
    Background: The knee-joint isokinetic profile (KJIP) injury risk factor may be modulated by chronological age, however, comparative data for elite male soccer players aged 25 years and older is lacking. Objective: To describe and compare the knee-joint isokinetic profile (KJIP) according to the chronological age of professional male soccer players. Method: In a cross-sectional study design, sixty-three soccer athletes from the first Chilean soccer division (A-series) were divided into younger and older groups (age ≤ 25 years; n = 35 and age > 25 years; n = 28, respectively). In both groups the IPKJ was assessed at 60°.s-1 in concentric mode. Results: The older group had lower extensor peak torque (p < .05). The younger group showed correlations between flexors peak torque and extensors mean power (p < .001). In the older group, flexors peak torque and flexors mean power were correlated. The flexors peak torque, total work, and mean power symmetric index (SI) exhibited values > 10 % for both groups. The extensors SI showed values > 10 % for mean power, although only in the older group. Conclusion: Several differences in the KJIP were noted between professional male soccer players aged ≤ 25 years and > 25 years. Current results offer injury prevention insights, discussed in the current manuscript.
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    Isokinetic force-power profile of the shoulder joint in males participating in CrossFit training and competing at different levels
    (PeerJ, 2021) Torres-Banduc, Maximiliano A.; Jerez-Mayorga, Daniel; Moran, Jason; Keogh, Justin W.L.; Ramírez Campillo, Rodrigo
    Background: As participants who engage in CrossFit training and competition perform a large volume of high intensity overhead activities, injuries to the shoulder are one of the most common in this sport. Previous research in other sports has indicated that the isokinetic force power profile of the shoulder joint (IPSJ) rotator muscles may assist in the prediction of shoulder injury. Aim: Therefore, the objective of this study was to determine the IPSJ in males engaged in CrossFit training at different competitive levels. Methods: In a cross-sectional study design, participants (age, 24.1 ± 2.7 years) classified as ‘beginner’ (n = 6), ‘intermediate’ (n = 7) or ‘advanced’ (n = 9) provided informed consent to participate in this study. The IPSJ assessment involved rotational and diagonal movements, including internal and external shoulder rotator muscles, at both 180.s−1 and 300.s−1. The variables analysed were peak torque/body mass (%), mean power (W) and the external/internal peak torque/body mass ratio (%). A Kruskal–Wallis test was used to compare the IPSJ of the three groups, with Dunn’s test used for post-hoc analysis. The alpha level was set at p < 0.05. Results: The IPSJ showed greater torque and power values in those who competed at the advanced level as compared to those at a lower competitive level (i.e. intermediate, beginner). This was observed mainly for the internal rotation and internal diagonal movements at both 180.s−1 and 300.s−1 . However, such differences between competitive levels were, in general, absent for the external rotation and external diagonal movements. Moreover, the participants from the advanced competitive level exhibited an imbalance of peak torque between the muscles responsible for the external–internal rotational and external-internal diagonal movements of the shoulder (i.e. peak torque external/internal ratio <66%), particularly in the dominant shoulder. Conclusion: These findings suggest greater development of the shoulder internal rotators and a higher probability of shoulder injury in CrossFit athletes at the advanced competitive level. Based on these results, participants engaged in CrossFit training and competition may wish to increase the volume of training for the shoulder external rotator muscles to complement the large increases in shoulder internal rotator strength that occur as a part of their regular training regimes.
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    The Mediating Role of the Muscle Quality Index in the Relation of Screen Time and Abdominal Obesity with Health-Related Quality of Life in Chilean Schoolchildren
    (2023-01-31) Delgado-Floody, Pedro; Gómez-López, Manuel; Caamaño-Navarrete, Felipe; Valdés-Badilla, Pablo; Jerez-Mayorga, Daniel
    Screen time (ST) and abdominal obesity have a negative effect on health-related quality of life (HRQoL). However, there is little information regarding the mediating role of the muscle quality index (MQI) in these relationships. The aim of the present study was to investigate the association between HRQoL, physical status (i.e., anthropometrics and fitness), lifestyle (i.e., ST and physical activity), and the MQI, and then to determine the potential mediating role of the MQI in the relation of ST and abdominal obesity with HRQoL in Chilean schoolchildren. The cross-sectional study included 750 schoolchildren (girls, n = 332 and boys, n = 418) aged between 10 and 14 years (11.73 ± 1.08 y). MQI, lifestyle, fitness parameters, waist-to-height ratio (WtHR) and HRQoL were measured. HRQoL presented a significant correlation with WtHR (r: −0.19), VO2max (r: 0.20), physical activity after school (r: 0.26), ST (r: −0.26) and MQI (r: 0.15). According to MQI, the high-MQI group reported higher HRQoL than the low-MQI group (low MQI: 36.10 ± 3.63 vs. high MQI: 37.43 ± 4.00, p < 0.001). In the mediation model, ST and abdominal obesity were negatively linked to HRQoL; the indirect effect confirmed that MQI is a partial mediator in the relation between ST and HRQoL (indirect effect = −0.04; SE = 0.02; 95% CI: −0.09, −0.01) and in the relation between abdominal obesity and HRQoL (indirect effect = −1.81; SE = 0.83; 95% CI: −3.41, −0.40). In conclusion, MQI is related to better HRQoL in schoolchildren, and the negative relation of ST and abdominal obesity with HRQoL is mediated by MQI.