Zengyuan Yue

Effects of Resistance Training in Children and Adolescents: A Meta-analysis

CONTEXT: Although physiologic benefits of resistance training for children and adolescents have been well documented, the impact of age and maturity on trainability of muscle strength remains poorly understood. OBJECTIVE: To assess the effects of resistance training in different age groups and maturity levels. METHODS: We searched electronic bibliographic databases, key journals, and reference lists of reviews, book chapters, and articles. Two independent reviewers evaluated the effects of resistance training on muscle strength for prepubertal and postpubertal healthy children and adolescents (younger than 18 years) by using the results of randomized and nonrandomized controlled trials. Assessments of muscle endurance and motor performance tests (eg, vertical jump) were excluded. The influence of continuous and categorical moderator variables was assessed by meta-regression and subgroup analyses, respectively. RESULTS: The overall weighted effect size of 1.12 (95% confidence interval: 0.9–1.3) was significantly greater than 0 (P < .01). Subgroup analyses revealed “maturity” to be a significant categorical moderator variable (z = 2.50; P = .01) and positive correlation coefficients were found for the continuous variables “duration” (r = 0.28; P = .02) and “frequency” (r = 0.26; P = .03). CONCLUSIONS: The results of our analysis indicate that the ability to gain muscular strength seems to increase with age and maturational status, but there is no noticeable boost during puberty. Furthermore, study duration and the number of performed sets were found to have a positive impact on the outcome.

Mechanical Load and Physiological Responses of Four Different Resistance Training Methods in Bench Press Exercise

Abstract Buitrago, S, Wirtz, N, Yue, Z, Kleinöder, H, and Mester, J. Mechanical load and physiological responses of four different resistance training methods in bench press exercise. J Strength Cond Res 27(4): 1091–1100, 2013—The purpose of the study was to compare the mechanical impact and the corresponding physiological responses of 4 different and often practically applied resistance training methods (RTMs). Ten healthy male subjects (27.3 ± 3.2 years) experienced in resistance training performed 1 exhausting set of bench press exercise until exhaustion for each of the following RTMs: strength endurance (SE), fast force endurance (FFE), hypertrophy (HYP), and maximum strength (MAX). The RTMs were defined by different lifting masses and different temporal distributions of the contraction modes per repetition. Mean concentric power (P), total concentric work (W), and exercise time (EXTIME) were determined. Oxygen uptake (V[Combining Dot Above]O2) was measured during exercise and for 30 minutes postexercise. Mean V[Combining Dot Above]O2, volume of consumed O2, and excess postexercise oxygen consumption (EPOC) were calculated over 30 minutes of recovery. Maximum blood lactate concentration (LAmax) was also determined postexercise. The P was significantly higher (p < 0.01) for FFE and MAX compared with that for SE and HYP. The W was significantly higher for FFE than for all other RTMs (p < 0.01), and it was also lower for SE than for MAX (p < 0.05). EXTIME for SE was significantly higher (p < 0.01) than for all other RTMs, whereas EXTIME for MAX was significantly lower (p < 0.01) than for all other RTMs. Mean V[Combining Dot Above]O2 was significantly higher during FFE than during all other RTMs (p < 0.01). Consumed O2 was significantly higher (p < 0.05) during SE than for HYP and MAX, and it was also significantly higher for FFE and HYP compared with MAX (p < 0.05). The LAmax was significantly higher after FFE than after MAX (p < 0.05). There were no significant differences in EPOC between all RTMs. The results indicate that FFE and MAX are adequate to train muscular power despite the discrepancy in the external load. Because FFE performance achieves the highest amount in mechanical work, it may also elicit the highest total energy expenditure. The FFE challenges aerobic metabolism most and SE enables the longest EXTIME, indicating both are appropriate to enhance aerobic muscular capacities. The EPOC and LA values may indicate that energy needs covered by anaerobic metabolism are not higher during HYP and MAX compared with the RTM of lower external load.

On the Cardiovascular Effects of Whole‐Body Vibration Part I. Longitudinal Effects: Hydrodynamic Analysis

For a given direction of whole-body vibration and a given piece of blood vessel, the local vibration has in general both a longitudinal (parallel) component and a lateral (perpendicular) component. The longitudinal and lateral effects are treated in Part I and Part II, respectively. In Part I, detailed hydrodynamic analysis shows that the maximal shear stress at the wall of the vessel is considerably increased by the longitudinal component of vibration for big vessels. For example, for high frequency range 40-50 Hz, the maximal shear stress at the wall of coronary artery could increase by 35-49% even if the local longitudinal amplitude is as small as 50 ¼m. Potential benefits and risks associated with this effect are discussed. In Part II, statistical analysis is carried out based on the results of specially designed experiments, where accelerations at different body locations and some cardiovascular parameters were measured simultaneously. Some changes of body mode were arranged during the vibration experiments in a way that the transmissibility of vibration increased considerably during each change of body mode. Statistical analysis of the results suggests with high level of confidence (>97%) that arterioles were dilated during such changes of body mode. Potential benefits associated with this effect are discussed.

Statistical Analysis for the Soccer Matches of the First Bundesliga

Statistical analysis for the soccer matches of the First Bundesliga; i.e., the first national soccer league of Germany, during the period Aug. 5 to Nov. 27, 2011 is made in order to see which parameters are more important for the result of a match. It is found that the goal efficiency, defined by the number of goals divided by the number of shots, is by far the most important parameter. The parameters of the second to the fourth importance are the number of shots, the number of passes and the number of ball contacts respectively. The present analysis shows that the quality of shots, represented by the goal efficiency, is more important than the quantity of shots for winning a soccer game. Regarding the long time dispute over the issue whether “direct play” or “possession play” is more effective, the present result favours “direct play” because it has higher goal efficiency compared to “possession play” according to the literature. Nevertheless, the length of passing sequence may not be the major factor related to the goal efficiency. Effective use of team possessions to create favourable shooting conditions may be more important for raising the goal efficiency. Much further analysis remains to be carried out in this direction.

A model analysis of the effects of wobbling mass on whole-body vibration

The effects of wobbling mass on the whole-body vibration are studied in terms of the comparison between two models A and B regarding their detailed behavior during the ‘whole-body vibration,’ where Model A is a system of four degrees of freedom with rigid and wobbling masses in both lower body and upper body, while Model B is a system of three degrees of freedom with a rigid upper body and is otherwise identical to Model A. Various quantities are calculated for both models. It is found that for the frequency range where the foot-to-upper-body transmission is important, the wobbling mass is able to reduce the transmissibility, to reduce the amplitude of the oscillation of the center of mass of the body, and therefore to reduce the amplitude of the fluctuation of the external force from the source of vibration. The model analysis reveals the mechanism for these reductions as follows: The oscillation of the wobbling mass in the upper body is carried by the oscillation of the rigid mass of the upper body and therefore the phase of the wobbling mass lags behind the phase of the rigid mass. For this reason, the average power which the wobbling mass in the upper body gives to the rigid mass of the upper body is negative.

A mathematical model for lactate transport to red blood cells

A simple mathematical model for the transport of lactate from plasma to red blood cells (RBCs) during and after exercise is proposed based on our experimental studies for the lactate concentrations in RBCs and in plasma. In addition to the influx associated with the plasma-to-RBC lactate concentration gradient, it is argued that an efflux must exist. The efflux rate is assumed to be proportional to the lactate concentration in RBCs. This simple model is justified by the comparison between the model-predicted results and observations: For all 33 cases (11 subjects and 3 different warm-up conditions), the model-predicted time courses of lactate concentrations in RBC are generally in good agreement with observations, and the model-predicted ratios between lactate concentrations in RBCs and in plasma at the peak of lactate concentration in RBCs are very close to the observed values. Two constants, the influx rate coefficient C1 and the efflux rate coefficient C2, are involved in the present model. They are determined by the best fit to observations. Although the exact electro-chemical mechanism for the efflux remains to be figured out in the future research, the good agreement of the present model with observations suggests that the efflux must get stronger as the lactate concentration in RBCs increases. The physiological meanings of C1 and C2 as well as their potential applications are discussed.

Statistical Analysis for the First Bundesliga in the Current Soccer Season

Statistical analysis for the 153 matches of First Bundesliga, i.e. the first national soccer league in Germany, in the first 17 “playing days” (August 10, 2013 to January 29, 2014) of the current soccer season was made. Various team parameters were compared between the winning and losing teams in the 118 non-drawing matches. The results support the conclusions of our earlier analysis (Yue, Broich, & Mester, 2014) that the quality of shots, represented by the goal efficiency, defined by the number of goals divided by the number of shots, is more important than the quantity of shots for winning a soccer game. This conclusion is also confirmed by the correlation analysis based on all the 153 matches: The correlation between the number of goals and the goal efficiency is found to be much stronger than the correlation between the number of goals and the number of shots. The team parameters of the second to the fourth importance are the number of shots, the number of passes and the number of ball contacts respectively. In contrast, the distance coverage is found to be statistically not important for winning a game.