The primary aim of the current study was to determine the time curves of changes in the record scores in the snatch and its variations during a two-year training cycle in young weightlifters. This study also aimed at assessing the ratios between these scores and at predicting the snatch record scores at the end of the subsequent annual training macrocycle. The final purpose was to compare the record scores with the isometric peak torque values of the trunk and knee extensors. The study involved 16 weightlifters who were tested seven times at three-month intervals. The overall mean ratios of the record scores in the hang snatch to those in the snatch and the record scores in the hang power snatch to those in the snatch were approximately constant and amounted to 0.95 and 0.79, respectively. The overall mean ratio between the scores in the power snatch to those in the snatch was approximately 0.88. Statistically significant differences (p < 0.05) between the individual time trajectories of record scores in the snatch and its derivatives were identified in two consecutive annual training macrocycles. The error in predicting record results at the end of the following annual training macrocycle was 6.7 ± 4.7% or 8.1 ± 3.4% depending on the way the measurement data were modeled. The results of the study also indicate that the measurements of the isometric peak torque of the trunk extensors performed in laboratory conditions can be useful in diagnosing the strength capacity of young weightlifters.
Introduction. The aim of the current study was to examine the relationship between knee and elbow isometric muscle torque values and the results obtained in special and specific exercises in young weightlifters. Material and methods. The study involved eight young weightlifters (age: 19.9 ± 4.3 years; height: 176.8 ± 10.6 cm; weight: 69.0 ± 19.7 kg -pretest, 70.9 ± 21.6 -posttest). Their performance put them in the second and third top classes of weightlifters their age according to the Polish norms for weightlifting (the so-called 'national class' and 'first class' in the Polish system, which are lower than the 'international class'). The differences between the values obtained in the first measurement of torque performed at the beginning of the preparation period and those obtained at the beginning of the immediate pre-competition period were compared with the differences in the maximal load lifted in special and specific exercises. Results. The training that the weightlifters underwent during the preparation period caused a significant increase in the relative torque values of the knee extensors (0.56 Nm/kg on average, p ≤ 0.047) and those of the elbow flexors (0.35 Nm/kg, p ≤ 0.0002). Significant differences (p ≤ 0.05) were observed between the results obtained in all of the special and specific exercises examined. A statistically significant relationship was also found between the changes in relative torque values and the results achieved in special and specific exercises. Conclusions. The regression equations derived in the study can help predict sports performance outcomes based on the results of laboratory tests.
Age-related decline in muscular force and power is an important prognostic indicator of functional impairments in older people. Most research has focused on the quadriceps and muscles which extend and flex the elbow and ankle joints as well as handgrip strength. To date, the strength of proximal and distal muscles of the upper limbs has not been compared in groups of active adults of differing ages. The aim of the study was to compare proximal muscles-expressed as torques of extension of the arm (ArmExt) and distal muscles-expressed as handgrip strength (HGS) in young and older physically active adults. This study examined 100 physically active volunteers without neuromuscular or central-nervous system disorders: 25 older males [OM] (68.3 ± 5.5 years) and 25 older females [OF] (67.0 ± 5.4) and a control group: 25 young males [YM] (21.2 ± 1.5) and 25 young females [YF] (21.3 ± 1.3). Strength measurements of the upper, dominant limb, were done under isometric contraction. The ArmExt measurement was done using Set Measurement Forces. For HGS measurement a hand dynamometer was used. The results showed no statistically significant differences in the ArmExt and ArmExt/kg of the OF and OM groups compared to the YF and YM groups, respectively. The HGS value for the OM group was statistically significantly lower than for the YM group. The HGS/kg in the OF and OM groups was statistically significantly lower than in the YF and YM groups, respectively too. Our results indicate a more pronounced effects of dynapenia being observed in distal muscles to compare with proximal ones in older physically active adults.
In the article comparison of time-frequency spectra of EMG signals obtained by the following methods: Fast Fourier Transform, predictive analysis and wavelet analysis is presented.The EMG spectra of biceps and triceps while an adult man was flexing his arm were analysed. The advantages of the predictive analysis were shown as far as averaging of the spectra and determining the main maxima are concerned. The Continuous Wavelet Transform method was applied, which allows for the proper distribution of the scales, aiming at an accurate analysis and localisation of frequency maxima as well as the identification of impulses which are characteristic of such signals (bursts) in the scale of time. The modified Morlet wavelet was suggested as the mother wavelet. The wavelet analysis allows for the examination of the changes in the frequency spectrum in particular stages of the muscle contraction. Predictive analysis may also be very useful while smoothing and averaging the EMG signal spectrum in time.
The article presents a proposal to use linear prediction method for a quick analysis of surface myoelectric (EMG) signals. The spectra obtained with the linear prediction (LP) and Fourier methods were compared. The LP method allows for a precise determination of the location and amplitude of the spectrum maximum and observation of changes in muscle tension and contraction phases. EMG spectra of brachial biceps during flexion and extension of the forearm by four adults were analyzed. The optimal width of the time window for the averaging of motor unit action potentials that allows for the observation of changes during contraction was established. It has been found that maximum spectrum during flexion has a significantly higher frequency and amplitude than during the extension of the forearm.
Age-related decline in muscular force and power is an important prognostic indicator of functional impairments in older people. Most research has focused on the quadriceps and muscles which extend and flex the elbow and ankle joints as well as handgrip strength. To date, the strength of proximal and distal muscles of the upper limbs has not been compared in groups of active adults of differing ages. The aim of the study was to compare proximal muscles -expressed as torques of extension of the arm (ArmExt) and distal muscles -expressed as handgrip strength (HGS) in young and older physically active adults. This study examined 100 physically active volunteers without neuromuscular or central-nervous system disorders: 25 older males [OM] (68.3 ± 5.5 years) and 25 older females [OF] (67.0 ± 5.4) and a control group: 25 young males [YM] (21.2 ± 1.5) and 25 young females [YF] (21.3 ± 1.3). Strength measurements of the upper, dominant limb, were done under isometric contraction. The ArmExt measurement was done using Set Measurement Forces. For HGS measurement a hand dynamometer was used. The results showed no statistically significant differences in the ArmExt and ArmExt/kg of the OF and OM groups compared to the YF and YM groups, respectively. The HGS value for the OM group was statistically significantly lower than for the YM group. The HGS/kg in the OF and OM groups was statistically significantly lower than in the YF and YM groups, respectively too. Our results indicate a more pronounced effects of dynapenia being observed in distal muscles to compare with proximal ones in older physically active adults.
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