This study aimed to investigate the relationship between knee extensors maximum voluntary contraction (MVC) torque and rate of torque development (RTD) with jump performance and with echography intensity (EI) from the vastus lateralis muscle (VL).
MethodsWe assessed the MVC torque and RTD from knee extensors by a standard isokinetic device from 16 male professional soccer players (25.5?±?3.9 years). Counter-movement jump (CMJ) and squat jump (SJ) height were calculated from their flight times. EI was determined from VL ultrasound images’ grayscale histogram acquired in the middle of the tight. Correlation between variables was investigated by the Pearson correlation coefficient.
ResultsWe observed a VL EI of 26.4?±?7.8 a.u., and the SJ and CMJ heights were 36.0?±?3.0 and 36.2?±?4.1 cm, respectively. There was a significant correlation between the MVC torque and absolute late-phase RTD (r?=?0.67 and 0.76—RTD200 and RTD250, respectively), between the CMJ height and absolute RTD50 (r?=?0.50), and between the normalized early-phase RTD and SJ height (r?=?0.53–0.60—RTD50 and RTD150). Additionally, normalized RTD200 (r?=?? 0.51) and RTD250 (r?=?? 0.56) were negatively correlated with EI.
ConclusionsSuch results suggest that athletes with the ability to produce torque explosively in the very beginning (between 50 and 150 ms) of knee extension can jump higher. Also, the muscle quality assessed by the VL IE seems to be more important to maximum strength and later periods of torque rise (>?200 ms).
相似文献Purpose
To examine effects of the peak torque angle (PTA) on the bilateral deficit (BD) index at two low velocities of contraction.Methods
Twenty young men performed right and left knee concentric extension–flexion (1 set, 5 repetitions) unilaterally and bilaterally in an isokinetic dynamometer at 30°/s and 60°/s. The peak torque (PT) from right, left and bilateral tests and their respective PTA were registered. Two BD indexes were determined as the bilateral PT divided by the summation of right and left PT (BDI1) and by the summation of left and right torque values found at the bilateral PTA (BDI2). Additionally, the mean of the absolute differences (MAD) between bilateral and unilateral PTAs was calculated as the mean of the modulus of the difference between bilateral minus right and bilateral minus left values divided.Results
The knee extensors showed difference between bilateral and unilateral PTA (p?<?0.01) and effect of velocity on bilateral PTA (p?<?0.05). MAD was not influenced by the direction of movement (p?=?0.673), whereas on knee flexors it depended on velocity (p?=?0.01). Knee extensors and flexors presented higher BDI1 than BDI2 at both velocities (p?<?0.001). The difference between BDI1 and BDI2 was strongly correlated with MAD (p?<?0.01).Conclusion
The BD is generally attributed to neural mechanisms, whereas the BD index was influenced by the PTA. Hence, it is suggested that the angle–torque relationship plays a role on the BD reported because it may enhance the BD index.Context:
Proprioception is essential to motor control and joint stability during daily and sport activities. Recent studies demonstrated that athletes have better joint position sense (JPS) when compared with controls matched for age, suggesting that physical training could have an effect on proprioception.Objective:
To evaluate the result of an 8-week strength-training program on shoulder JPS and to verify whether using training intensities that are the same or divergent for the shoulder''s dynamic-stabilizer muscles promote different effects on JPS.Design:
Randomized controlled clinical trial.Setting:
We evaluated JPS in a research laboratory and conducted training in a gymnasium.Patients or Other Participants:
A total of 90 men, right handed and asymptomatic, with no history of any type of injury or shoulder instability.Intervention(s):
For 8 weeks, the participants performed the strength-training program 3 sessions per week. We used 4 exercises (bench press, lat pull down, shoulder press, and seated row), with 2 sets each.Main Outcome Measure(s):
We measured shoulder JPS acuity by calculating the absolute error.Results:
We found an interaction between group and time. To examine the interaction, we conducted two 1-way analyses of variance comparing groups at each time. The groups did not differ at pretraining; however, a difference among groups was noted posttraining.Conclusions:
Strength training using exercises at the same intensity produced an improvement in JPS compared with exercises of varying intensity, suggesting that the former resulted in improvements in the sensitivity of muscle spindles and, hence, better neuromuscular control in the shoulder.Key Words: joint position sense, neuromuscular control, muscle spindlesKey Points
- Improvements in joint position sense can be attained via standard strength-training exercises.
- Performing resistance exercises at consistent intensity rather than varying intensity resulted in better proprioception performance.