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12Changes in maximum muscle torque of knee joint extensor muscles depending on various forms of warm-up in the training microcycle
UDC 796.015
Doctor of Science Paulina Szyszka1
1Department of Sports Sciences, Faculty of Physical Education and Health, in Biala Podlaska, Jozef Pilsudski Academy of Physical Education in Warsaw
Corresponding author:
Abstract
Objective of the study was to determine the changes of maximum muscle torque of knee joint extensor muscles under static conditions in the training microcycle using different protocols of warm-up exercises. The study included 5 training units in the preparatory period. The test procedure included 2 measurements during one training unit. The first measurement was taken before the warm-up, the second after the end of the warm-up, and before starting the proper part of the training. During the performance of individual training units, specific warm-up protocols were applied to 15 weightlifters.
A statistically significant (p<0.05) increase in the torque of knee joint extensor muscles between the measurements taken before and after warm-up was observed in the second (II) (p=0.001), fourth (IV) (p=0.04) and fifth (V) (p=0.001) measurement day, when dynamic exercises were used in the protocol. Average values after the application of vertical jumps in place caused an average increase in value by 7.52%. The results of the conducted analyses confirm the validity of dynamic exercises often used in practice after a long waiting time for an approach during the competition in weightlifting. Carrying out such measurements may be a guide for the trainer to select the exercises during the programming of the competition warm-up.
Keywords: warm-up, exercises, strength, knee joint, weightlifting.
Introduction. A generally accepted and recommended method of preparing the body for intensive activity is a 5 to 10 minute warm-up in the form of low and medium intensity exercises [6]. It is recommended to perform an appropriate form of warm-up before exercise to improve later results through changes in physiological and mental status [1]. The warm-up usually includes general and specific components [7], which are intended to increase muscle temperature [3]. In the general component, low impact exercises are recommended, such as aerobic exercises for 5-15 minutes at moderate intensity [1]. A specific component is realized by performing specific repetitions [7], used to prepare the nervous system and increase muscle activation [8]. Barnes (2016) found that thrust force when performing weightlifting exercises improved by at least 10% when an element specific for the movement was incorporated into the warm-up.
Studies have shown that dynamic stretching effectively increases elasticity, maximum muscle strength, sprint performance and vertical jump performance [10]. Studies were also conducted on the changes in muscle temperature under the influence of various forms of warm-up [7]. So far, no studies have been conducted to determine the influence of individual exercises used in the warm-up on the maximum muscle torque under static conditions. In weightlifting, the torque is used to evaluate the applied training loads [5,9]. Therefore, the aim of this study was to determine the changes in the maximum values of the muscle torque of knee joint extensor muscles in static conditions of athletes practicing weightlifting, with the administration of different warm-up exercises in the training microcycle.
Material and test methods. In the training microcycle from 26-30.08.2019 changes in the muscle
torque of the knee joint extensor muscles of 15 competitors in Olympic weightlifting (Table 1) were recorded with the administration of different warm-up protocols.
Table 1. Anthropometric data of the studied group of competitors
n Age [year] Body weight [kg] Body height [cm]
x 15 20,1 79,1 176,5
SD - 2,3 17,2 4,9
The study included 5 training units in the preparatory period. The test procedure included 2 measurements during one training unit. The first measurement was taken before the warm-up, the second after the end of the warm-up, and before starting the proper part of the training. During the execution of individual training units, specific warm-up protocols were applied:
I- general exercises + continuous run for 10 min, II- general exercises + jumps on the gearbox 5x5, IIIgeneral exercises + continuous run for 15 min, IV- general exercises + vertical jumps 5x5, V- general exercises + double-legged multi-jumps in 5x5 series. The general exercises in each protocol included the same set of shaping exercises. All participants or their parents have given their written consent to participate in the study. Participants were provided with information on the test procedure and the possible risks and benefits of participating in the test. The research was conducted in accordance with the ethical standards of the Declaration of Helsinki and the research was approved by the University Research Ethics Committee. The values of the maximum muscle torque of the knee joint extensor muscles under isometric conditions were determined at the angle of 90 degrees. The measurements were carried out at the measuring station LR2-P (JBA Zb. Staniak, Poland) [5]. During the test, the
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PRE POST 1 PRE POST II PRE POST III PRE POST IV PRE POST V
Figure 1. The values of maximum moments of muscle strength under static conditions of knee joint extensors before and after warm-up in subsequent measurement days.
subjects performed three repetitions of the straightening process no longer than 3 seconds. Torque values were displayed and recorded by the dynamometer and the best result was used in the analysis.
Results of studies. The changes in the maximum muscle torque of the knee joint extensor muscles of the weightlifters with the administration of different variants of the warm-up exercises are presented in Figure 1.
A statistically significant (p<0.05) increase in the maximum muscle strength moments of knee joint extensors between the measurement before and after warm-up was observed in the second (II) (p=0.001), fourth (IV) (p=0.04) and fifth (V) (p=0.001) measurement day. Average values after the application of vertical jumps in place caused an average increase in value by 7.52%. The highest d Cohen effect was confirmed for the V attempt (0.48). After applying the continuous run for 15 minutes, the maximum muscle torque of knee joint extensor muscles decreased by 3.96 Nm among the studied group of competitors. Minor changes of 1.07% were observed in the 10-minute continuous run (I).
Summary and conclusions. The aim of the study was to determine the changes of maximum muscle torque of knee joint extensor muscles under static conditions in the training microcycle using different protocols of warm-up exercises. The measurement of the maximum torque of knee joint extensor muscles in weightlifting athletes should be preceded by a dynamic warm-up, because after these exercises we have observed a significant increase in the torque of knee joint extensor muscles compared to the pre-warm-up measurements (Figure 1).
The literature review indicates that this part of the training should lead to changes in physiological and mental state [1], as well as change muscle temperature [3]. The research indicates that it is important to use exercises with a similar structure as the exercises in the proper part of the training in order to increase the strength capabilities of the competitor by as much as 10% [2]. However, no studies were conducted to determine the changes in strength capabilities under the influence of the use of different exercises in the warm-up.
The results of our analyses correspond to those of scientists observing the influence of dynamic stretching during warm-up on the strength parameter [4]. The authors suggest that dynamic stretching is an effective technique for increasing muscle performance, but the mechanism by which dynamic stretching improved leg strength is not clearly defined. Based on the results of this study and according to data presented by Church (2001) and Yamaguchi (2005), it is assumed that muscle performance has improved by increasing muscle temperature or amplifying activation caused by the contractions of the target muscles' antagonists. Carrying out such measurements may be a guide for the trainer to select the exercises during the programming of the competition warm-up. The results of the analy-
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sis also confirm the validity of dynamic exercises often used in practice (e.g. vertical jumping upwards) after a long period of waiting for an approach during weight-lifting competitions.
References
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