The effectiveness of isometric conditioning activity (CA) is not well described in terms of the level of performance enhancement and the presence of a stretch and shortening cycle in subsequent explosive tasks. Therefore, the aim of this study was to evaluate the effect of a maximum isometric squat as the CA and a subsequent squat jump (SJ) and countermovement jump (CMJ) height. A total of 31 semi-professional handball and soccer players were randomly assigned to two different conditions: (i) 3 sets of 3 repetitions (each lasting 3 s) of maximum isometric back squats (EXP), and (ii) no CA (CTRL). The jump height measurements were performed 5 min before the CA and approximately at the 4th and 8th minute following the completion of the CA. Due to the high inter-individual variability in the potentiation responses, the best value obtained post-CA was also analyzed. The SJ height significantly increased from baseline to the 8th minute post-CA (p = 0.004; ES = 0.31; Δ = +3.1 ± 5.0%) in the EXP condition. On the other hand, the CMJ height was significantly higher in the 4th (p = 0.001; ES = 0.23; Δ = +2.7 ± 3.7%) and 8th minute post-CA (p = 0.005; ES = 0.32; Δ = +3.6 ± 5.7%) in comparison to baseline during the EXP condition. Furthermore, SJ height significantly increased from baseline to the best time-point during the EXP (p < 0.001; ES = 0.47; Δ = +4.9 ± 4.9%) and CTRL (p = 0.038; ES = 0.21; Δ = +2.5 ± 5.8%) condition. Moreover, the CMJ height was significantly higher at the best time-points than at the baseline during EXP (p < 0.001; ES = 0.53; Δ = +5.6 ± 4.7%) and CTRL (p = 0.002; ES = 0.38; Δ = +3.1 ± 5.2%) condition. The findings from this study indicate that a maximum isometric squat, used as a CA, effectively improved SJ and CMJ height. This suggests that the presence or absence of a stretch and shortening cycle in both CA and post-CA tasks does not significantly impact the post-activation performance enhancement response.

• MeSH
• fotbal * MeSH
• lidé MeSH
• postura těla MeSH
• sporty * MeSH
• svalová síla fyziologie   MeSH
• tělesná výška MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

The objectives of this study were related to the research of the relations between the abilities of professional basketball players in the performance of one repetition maximum (1RM) back squat and explosive movements, such as 5, 10 and 20-metre running, and vertical jump; as well as the detection and comparison of these abilities between players who play on the outside and inside positions. The study involved 35 professional basketball players (22 outside and 13 inside) who were selected as candidates for the national team of Bulgaria. Independent variables of muscular strength were obtained by applying the 1RM back squat test (142.06 ± 29.31 kg), and were normalized with respect to the body mass (1RM Squat/kg (1.51 ± 0.25)) and by applying suitable allometric exponent (1RM SquatAl (6.86 ± 1.16)). Dependent variables were obtained using two tests: 20-metre run (times registered at 5 and 10 metres) and vertical jump (used to calculate the variable peak anaerobic power (PAPW)). The results indicated that none of the variables of strength were significantly related to the speed performance, while moderate correlations occurred between the normalized strength variables (1RM Squat/kg and 1RM SquatAl) and vertical jump (r = 0.310 and r = 0.308 / p < 0.05). The results obtained show greater correlation (r = 0.660 / p < 0.01) in the ability to deliver power when performing squat and mechanical work performed in vertical jumps. Outside and inside players were significantly different in three variables only: peak anaerobic power, body height and body weight.

• MeSH
• anaerobní práh MeSH
• basketbal * MeSH
• biomechanika * MeSH
• dospělí MeSH
• kosterní svaly MeSH
• lidé MeSH
• lokomoce MeSH
• mladý dospělý MeSH
• sportovní výkon MeSH
• svalová síla * MeSH
• tělesná výkonnost MeSH
• zádové svalstvo MeSH
• zátěžový test metody   MeSH
• zrychlení MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH

The purpose was to investigate whether runners who do not squat their body weight once will not be overloaded with a weight vest with a load of 5% of BW and will not maintain 95% intensity across ten repetitions of a 20-meter sprint. Eight adult female students (24,05±1,15 years old; body height 168±4,24 cm; body weight 60,39±5,53 kg) from the faculty of sports studies at Masaryk University in the Czech Republic participated in this study. Categories were: 1 = NBW (1RM in the squat is relative body weight ± 5 kg), 2 = LBW (1RM in the squat is lower than BW-5 kg) and 3 = HBW (1RM in the squat is higher than BW +5 kg). The measurements took place on three different days, each day running with another experimental condition: free sprinting, weighted vest sprinting with a 5% load of BW, and weighted vest sprinting with a 5% load of 1RM squat. With a weight vest with resistance at the level of 5% of body weight, during 49 sprints, the intensity decreased by a maximum of 4.82% (participant 4, NBW group, 1st run). Although, with weight vest resistance at the level of 5% of the 1RM back squats, during 68 sprints, the intensity decreased by a maximum of 6.59% (participant 1, NBW group, 8th run). It seems that the level of strength abilities of the lower limbs did not play a role in this, we can calculate 5% intensity from both BW and 1 RM squat. Since the HBW group could maintain the required intensity even at significantly higher weights than 5% BW, further research with a larger research sample is needed.

Krzysztofik, M, Wilk, M, Pisz, A, Kolinger, D, Tsoukos, A, Zając, A, Stastny, P, and Bogdanis, GC. Acute effects of varied back squat activation protocols on muscle-tendon stiffness and jumping performance. J Strength Cond Res 37(7): 1419-1427, 2023-Intensity, movement velocity, and volume are the principal factors to successfully use postactivation performance enhancement. Therefore, 15 resistance-trained volleyball players completed 3 different back squat configurations as a conditioning activity (CA) in randomized order: (a) 3 sets of 3 repetitions at 85% 1RM (HL); (b) a single set of back squats at 60% 1RM until 10% mean velocity loss (VB); (c) and 2 sets of back squats at 60% 1RM until 10% mean velocity loss (2VB) on subsequent countermovement jump performance, Achilles tendon, and vastus lateralis stiffness with concomitant front thigh skin surface temperature assessment. The measurements were performed 5 minutes before the CA and at 2, 4, 6, 8, and 10 minutes. The jump height was significantly increased in the second minute and at peak, post-CA compared with baseline for all conditions ( p = 0.049; ES = 0.23 and p < 0.001; ES = 0.37). Skin surface temperature was significantly increased for all post-CA time points compared with baseline in the 2VB condition ( p from <0.001-0.023; ES = 0.39-1.04) and in the fourth minute and at peak post-CA in HL condition ( p = 0.023; ES = 0.69 and p = 0.04; ES = 0.46), whereas for the VB condition, a significant decrease in peak post-CA was found ( p = 0.004; ES = -0.54). Achilles tendon stiffness was significantly decreased for second, fourth, eighth, 10th, and peak post-CA in comparison to baseline for all conditions ( p from p = 0.004-0.038; ES = -0.47 to -0.69). Vastus lateralis stiffness was significantly decreased for peak post-CA compared with baseline for all conditions ( p = 0.017; ES = -0.42). We recommend using a single set of barbell squats with a 10% velocity loss as a mechanism of fatigue control to acutely improve jump height performance and avoid unnecessary increases in training volume.

• MeSH
• Achillova šlacha * MeSH
• kosterní svaly fyziologie   MeSH
• lidé MeSH
• odporový trénink * metody   MeSH
• postura těla MeSH
• svalová síla fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

PURPOSE. Squats are among the basic exercises that have become an integral part of exercise programs. It is commonly used by athletes in many sports. Its potential is shown in the development of strength, power, and overall sports performance. The aim of the study was to verify inconsistent views on deep squats, technical design, and related health risks. METHODS. For the purposes of the review, the terms "squat, knee, biomechanics, deep, patellofemoral, back squat, performance, arthritis, health, injury, risk" were used. RESULTS. It turns out that the technique of performing a deep squat has its strict principles, which must be respected and which have a significant impact on the benefits and risks. From loading, the lower position represents an increase in compressive and shear forces on the patellofemoral joint, however, this is a natural state that is not risky. Health hazards cannot be based on analytical-mathematical models, which are insufficient in this aspect. Extreme long-term exposure carries the risk of permanent consequences in the form of osteoarthritis. For prophylaxis or convalescence, it is possible to use effective aids like sleeves, kinesio taping, bandage or "knee savers". CONCLUSIONS. With optimal technique and sensible exercise selection, there is no greater risk in healthy individuals without degenerative anatomical changes. In order to assess the effects of the squat forces on the ankle, knee, hip, spine, it is necessary to consider the technique and also individual anatomical differences.

Eight resistance-trained men completed three protocols separated by 48-96 hours. Each protocol included 36 repetitions with the same rest duration, but the frequency and length of rest periods differed. The cluster sets of four (CS4) protocol included 30 s of rest after the 4th, 8th, 16th, 20th, 28th, and 32nd repetition in addition to 120 s of rest after the 12th and 24th repetition. For the other two protocols, the total 420 s rest time of CS4 was redistributed to include nine sets of four repetitions (RR4) with 52.5 s of rest after every four repetitions, or 36 sets of single repetitions (RR1) with 12 s of rest after every repetition. Mean (MF) and peak (PF) force, velocity (MV and PV), and power output (MP and PP) were measured during 36 repetitions and were collapsed into 12 repetitions for analysis. Repeated measures ANOVA 3 (protocol) x 12 (repetition) showed a protocol x repetition interaction for PF, MV, PV, MP, and PP (p-values from <0.001 to 0.012). No interaction or main effect was present for MF. During RR1, MV, PV, MP, and PP were maintained, but decreased throughout every 4-repetition sequence during CS4 and RR4. During CS4 and RR4, PF was less following a rest period compared to subsequent repetitions, whereas PF was maintained during RR1. These data indicate that rest redistribution results in similar average kinetics and kinematics, but if total rest time is redistributed to create shorter but more frequent sets, kinetics and kinematics may remain more constant.

• Publikační typ
• časopisecké články MeSH

The objective of this study was to compare (i) The effects of a flywheel and free-weight resistance training program; and (ii) The effects of performing lateral and frontal split squats as part of a flywheel-resistance training program on jumping performance, the 5-0-5 change of direction test time, and the one-repetition maximum (1RM) back squat in soccer players. Twenty-four male amateur soccer players participated in this study and were randomly and equally assigned to one of three different test groups: forward split-squat group (FSQ); lateral split-squat group (LSQ); and free-weight training group (TRAD). Athletes in the FSQ group performed a squat and a forward split squat on a flywheel device, while those in the LSQ group performed a squat and a lateral split squat (instead of a forward split squat) on a flywheel device. Each training lasted 4 weeks. The main finding was that all training groups, such as TRAD, FSQ, and LSQ, significantly improved broad jump length (p = 0.001; effect size [ES] = 0.36), 5-0-5 COD time with a turn on the dominant limb (p = 0.038; ES = 0.49), and 1RM back squat (p = 0.001; ES = 0.4). In turn, both flywheel-resistance training groups (FSQ and LSQ) significantly improved their counter-movement jump height (p = 0.001; ES = 0.8 and p = 0.002; ES = 0.58; respectively) with no effect in the TRAD (p = 0.676; ES = 0.07) training group. Both free-weight and flywheel-resistance training lasting 4 weeks performed in-season contributed to significant improvement in 1RM back squat, broad jump performance, and 5-0-5 change of direction testing time, while flywheel-resistance training might be superior in counter-movement jump height enhancement in soccer players. Moreover, the manner in which split squats were performed was not a factor influencing the obtained results.

• Publikační typ
• časopisecké články MeSH

Tufano, JJ, Conlon, JA, Nimphius, S, Oliver, JM, Kreutzer, A, and Haff, GG. Different cluster sets result in similar metabolic, endocrine, and perceptual responses in trained men. J Strength Cond Res 33(2): 346-354, 2019-The purpose of this study was to compare the kinematic, metabolic, endocrine, and perceptual responses of 3 back squat protocols with equal loads, number of repetitions, and total rest duration. Eight strength-trained men performed 36 back squats using 75% 1 repetition maximum and 420 seconds of total rest during basic cluster sets of 4 (CS4), rest redistribution sets of 4 (RR4), and rest redistribution sets of 1 (RR1). Rating of perceived exertion (RPE), blood lactate (La), mean velocity maintenance (MVM), and mean velocity loss (MVL) were measured during exercise. Total testosterone (TT), growth hormone (GH), cortisol (C), and sex hormone-binding globulin (SHBG) were measured before exercise and 15, 30, and 60 minutes postexercise. There were no differences between protocols for MVM. However, MVL was less during RR1 compared with RR4 (p = 0.032), and neither protocol was different than CS4. All protocols resulted in similar increases in RPE and La, which remained elevated up to 30 minutes postexercise (p ≤ 0.05). In all protocols, GH increased and returned to baseline by 60 minutes postexercise (p ≤ 0.05). At 60 minutes postexercise, TT was less than all other time points (p ≤ 0.05). There were no main effects for time for SHBG or C. The data from this study show that different types of cluster set protocols can result in proanabolic physiological responses to resistance training. In addition, coaches can redistribute rest periods without affecting perceived effort or metabolic and hormonal changes if the external load, number of repetitions, and total rest time are equalized.

• MeSH
• dospělí MeSH
• globulin vázající pohlavní hormony analýza   MeSH
• hydrokortison krev   MeSH
• kosterní svaly fyziologie   MeSH
• kyselina mléčná krev   MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• odpočinek fyziologie   MeSH
• odporový trénink metody   MeSH
• percepce MeSH
• růstový hormon krev   MeSH
• tělesná námaha fyziologie   MeSH
• testosteron krev   MeSH
• záda MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• randomizované kontrolované studie MeSH

PURPOSE Many types of vertical jumps (VJ) are commonly used to assess the development of the level of explosive strength of lower limbs achieved after a training period. This study is focused on comparing various parameters of different types of VJ with 1 RM in Olympic-style weightlifting, squat and deadlift with an Olympic bar. he snatch r=0.8 r2= 0.64, clean and jerk r=0.81 r2= 0.65, back squat r=0.82 r2= 0.67 and deadlift r=0.78 r2= 0.60; for the SJ with hands on the hips and the snatch r= 0.76 r2= 0.57, clean and jerk r= 0.75 r2= 0.56, back squat r= 0.77 r2= 0.59 and deadlift r= 0.71 r2= 0.50. Significant correlation coefficients were not found for 1 RM in the snatch, clean and jerk, back squat and deadlift and the CMJ or SJ with and without arm swing in any of the following parameters: jump height (m), relative force (% of body weight), relative power output (W/kg of body weight). CONCLUSION The main finding is that the jump height (m) of the CMJ or SJ with or without arm swing did not correlate significantly with 1 RM in the snatch, clean and jerk, back squat and deadlift. Therefore, jump height measurement can be used as a motivation tool but not to predict maximum strength in Olympic bar exercises, or vice versa. We recommend using the average power output (W) parameter in the CMJ with using arms as a predictor of current performance level in exercises with an Olympic bar for men and women.

• MeSH
• lidé MeSH
• pohybová aktivita MeSH
• sportovci MeSH
• sportovní výkon MeSH
• tělesná námaha MeSH
• vzpírání * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH

Introduction: Ice hockey is a power-speed sport played on ice. The surface specification is very different from a normal surface, so it is important to look for the most appropriate measurements and specific off-ice tests that would better define ice-hockey performance. Therefore, the main purpose of this research was to determine the relationship of rate of force development (RFD) in back squat with commonly used off-ice and on-ice tests. Methods: The research involved 15 junior ice-hockey players (181.8 ± 4.1 cm; 80.7 ± 8.8 kg; 18.4 ± 0.9 yrs) playing in the highest competition of Czech hockey. Players performed all tests in one day divided into 2 blocks - off-ice block (OFF) in the morning and on-ice block (ON) in the afternoon, respectively. The OFF contained 30 m sprint test with 15 m split (SP15; SP30), plyometric tests (broad jump - BJ; countermovement jump - CMJ), and a velocity squat protocol (VSP). Finally, in the ON was performed speed and coordination tests - 30 m forward skating with 15 m split (FW15 and FW30); 30 m backward skating with 15 m split (BW15 and BW30); Weave agility test (WAT); Transition test (TT) and Pro-agility test (PAT). Results: No significant results were found between RFD and coordination tests (TT, WAT, PAT) and CMJ. The significant correlations were found between RFD40kg and SP30 (r = -.865; p < .01) and BJ and RFD40kg, respectively (r =.649; p < .05). However, as the back squat loads increase, the correlation strength decreases between RFD and SP30 (r = -.677; p < .01 for RFD50kg and r = -.560; p < .05 for RFD60kg). Moreover, the strong degree of correlation were observed between RFD40kg and FW15 (r = -.699; p < .05) and also FW30 (r = -.705; p < 0.05). Conclusion: The results of the study show a significant relationship between the RFD and commonly used off-ice and on-ice tests.