Changes In Isokinetic Strength Research Articles

Effect of long-term training adaptation on isokinetic strength in college male volleyball players

Background and Study Aim: Most of this study focused on endurance, power, and anthropometric measurements but no research declared isokinetic strength changes during two years. The purpose of this study was to assess the effect of resistance exercises on two seasonal alters in isokinetic strength of knee muscles at different angular velocities, in college volleyball players. Material and Methods: Thirteen college volleyball players, (age: 21.75 years, body mass: 78.60 kg, and height: 187.0 cm) participated in the study. All college volleyball players take part in the two-year (8 month each year) volleyball-specific training and competitions. The measurement of peak isokinetic concentric knee extension and knee flexion torque in both legs were taken at 2 angular velocities of movement, low at 60° s-1, and intermediate at 180° s-1. Results: The pre- and post-test values of the peak isokinetic strength found that statistical significance difference, at 60° s-1 and 180° s-1 for knee extensor-flexor both dominant and non-dominant in favor of post-tests. Significant enhances were observed in the baseline dominant knee extensor-flexor muscle strength (extensor knee strength 60° s-1: 19.0%, 180° s-1: 20.5%, flexor knee strength, 60° s-1: 33.4%, 180° s-1: 31.4%) respectively. Non-dominant knee extensor-flexor muscle strength increased significantly over the two-year period (extensor knee strength 60° s-1: 21.3%, 180° s-1: 23.0%, flexor knee strength, 60° s-1: 37.4%, 180° s-1: 33.9%) respectively. Conclusion: As a result, our data suggests that the two-year planned program of specific volleyball and resistance training can increase the knee muscle extensor-flexor strength and H:Q ratios of volleyball players. Especially, at a 60° s-1 and 180° s-1 angular velocities, whilst the knee muscle extensor-flexor strength and H:Q ratios for dominant and non-dominant legs were increasing, also H:Q ratios disproportion were decreasing. Therefore, these alters indicated that regular specific-volleyball and resistance training can increase knee muscle extensor-flexor strength and H:Q ratios for dominant and non-dominant legs.

Assessing differential responders and mean changes in muscle size, strength, and the crossover effect to 2 distinct resistance training protocols.

The objective of this study was to determine differences in 2 distinct resistance training protocols and if true variability can be detected after accounting for random error. Individuals (n = 151) were randomly assigned to 1 of 3 groups: (i) a traditional exercise group performing 4 sets to failure; (ii) a group performing a 1-repetition maximum (1RM) test; and (iii) a time-matched nonexercise control group. Both exercise groups performed 18 sessions of elbow flexion exercise over 6 weeks. While both training groups increased 1RM strength similarly (∼2.4 kg), true variability was only present in the traditional exercise group (true variability = 1.80 kg). Only the 1RM group increased untrained arm 1RM strength (1.5 kg), while only the traditional group increased ultrasound measured muscle thickness (∼0.23 cm). Despite these mean increases, no true variability was present for untrained arm strength or muscle hypertrophy in either training group. In conclusion, these findings demonstrate the importance of taking into consideration the magnitude of random error when classifying differential responders, as many studies may be classifying high and low responders as those who have the greatest amount of random error present. Additionally, our mean results demonstrate that strength is largely driven by task specificity, and the crossover effect of strength may be load dependent. Novelty Many studies examining differential responders to exercise do not account for random error. True variability was present in 1RM strength gains, but the variability in muscle hypertrophy and isokinetic strength changes could not be distinguished from random error. The crossover effect of strength may differ based on the protocol employed.

Effects of the FIFA 11+ on ankle evertors latency time and knee muscle strength in amateur futsal players

Background: The FIFA 11+ has shown to increase muscle strength and reduce injury risk. The purpose of this study was to assess the short and long-term effects of the FIFA 11+ on knee strength, and muscle latency after sudden inversion of amateur futsal players. Methods: Seventy-one male futsal players were recruited and randomized to a FIFA 11+ (n = 37, age: 27.0 ± 5.1 years) and a control group (n = 34, age: 26.0 ± 5.1 years). The FIFA 11+ programme was executed twice a week, for 10 weeks, followed-up after 10 weeks where both groups executed regular warm-ups. Concentric and eccentric isokinetic knee muscle strength was tested and latency time of the evertor muscles after sudden inversion of the ankle was executed with a trapdoor mechanism following an EMG protocol of selected leg muscles (peroneus brevis and peroneus longus). Results: No significant difference were observed between groups for short-term changes in isokinetic strength after adjustment for baseline differences. At long-term, significant gains were obtained after adjustment for baseline differences in eccentric strength for both lower limbs as for the H/Q ratios for the dominant limb. No changes between groups were observed in the peroneus brevis and peroneus longus latency time. Conclusions: Performing FIFA 11+ did not have short-term effects on knee strength and muscle latency after sudden inversion in amateur futsal players. However, significant long-term benefits were observed for eccentric strength and H/Q ratios.

Multiple Strength Assessments to Evaluate Adaptations to High-Load and Low-Load Blood Flow Restricted Exercise

Differences in muscle strength adaptations between high-load (HL) and low-load blood flow restricted (BFR) resistance training protocols may be due to the type of strength test performed (e.g isotonic, isokinetic and isometric). PURPOSE: To assess differences in isotonic, isometric and isokinetic strength adaptations in older adults following HL and BFR resistance training. METHODS: Thirty-six males and females (mean: 75.6+7.6 years, 1.67+.09 m, 74.3+13.2 kg) classified as being at risk of mobility limitations were randomly assigned to HL (70% 1-RM) or low-load BFR (30% 1-RM coupled with a vascular restriction) exercise for the knee extensors twice per week for 6 weeks. A control group performed light upper body resistance and flexibility training. Knee extension 10-RM to predict 1-RM strength, isometric maximum voluntary contraction (MVC) and isokinetic strength at 60[BULLET OPERATOR]s-1, 180[BULLET OPERATOR]s-1, and 300[BULLET OPERATOR]s-1were measured before and after 6-weeks of training. RESULTS: HL and BFR training increased predicted 1-RM strength 34% (P<.001) and 24% (P<.001) respectively, from baseline to 6-weeks of training. HL training produced a 16% increase in MVC (P=.002) while BFR training did not change (P=.91). No interventions, included the control, resulted in changes in isokinetic strength at the various speeds (P>.20). CONCLUSION: Strength improvements from HL resistance training carried over to other strength tests. This favorable adaptation did not occur following BFR exercise which may limit the effectiveness of this training program. Isotonic training does not carry over to isokinetic strength adaptations and therefore may be a drawback when implementing resistance training programs for older adults. Supported by NIH grant 1R15 A6040700-01A1.

Changes in Isokinetic Muscle Strength in Adolescent Soccer Players after 10 Weeks of Pre-Season Training

Background:During soccer-specific movements, the strength of knee extensors and flexors is of great importance and achieving certain strength ratios between the two has been identified as an important parameter for reducing the risk of soft tissue injuries around the knee.Objective:The aim of the study was to evaluate changes in isokinetic strength of the knee flexors and extensors and their strength ratios in elite adolescent soccer players.Methods:Before and after 10 weeks of standard pre-season soccer training with progressive eccentric hamstring exercises, the players (n=18; age 17.1±0.4 years) participated in isokinetic testing to assess concentric and eccentric peak torque at 60°·s-1.Results:After 10 weeks of training, the peak eccentric torque of the non-dominant quadriceps increased (p=0.018; ω=0.24). Additionally, the average eccentric work increased in the dominant hamstrings (p=0.007; ω=0.23), dominant quadriceps (p=0.02; ω=0.31), non-dominant hamstrings (p=0.003; ω=0.25 and non-dominant quadriceps (p=0.01; ω=0.37). Lastly, the isokinetic functional ratio (eccentric hamstrings-to-concentric quadriceps) increased in favor of eccentric hamstring strength in the non-dominant limb (p=0.04; ω=0.31).Conclusion:The results of the study indicate that pre-season training induced suboptimal changes in the isokinetic strength of the knee flexors and extensors in elite adolescent soccer players. However, the lack of injuries combined with an apparent lack of preparedness explained by slow velocity isokinetic testing indicates that future research should investigate other forms of strength testing to determine soccer-specific preparedness such as isokinetic dynamometry at higher speeds (i.e.180°.s-1or 240°.s-1) and traditional weight-room testing such as 1RM tests.

Isokinetic Strength Changes Following Long-Duration Spaceflight on the ISS.

Long-duration spaceflight results in a loss of muscle strength that poses both operational and medical risks, particularly during emergency egress, upon return to Earth, and during future extraterrestrial exploration. Isokinetic testing of the knee, ankle, and trunk quantifies movement-specific strength changes following spaceflight and offers insight into the effectiveness of in-flight exercise countermeasures. We retrospectively evaluated changes in isokinetic strength for 37 ISS crewmembers (Expeditions 1-25) following 163 ± 38 d (mean ± SD) of spaceflight. Gender, in-flight resistance exercise hardware, and preflight strength were examined as potential modifiers of spaceflight-induced strength changes. Mean isokinetic strength declined 8-17% following spaceflight. One month after return to Earth, strength had improved, but small deficits of 1-9% persisted. Spaceflight-induced strength losses were not different between men and women. Mean strength losses were as much as 7% less in crewmembers who flew after the Advanced Resistive Exercise Device (ARED) replaced the interim Resistive Exercise Device (iRED) as the primary in-flight resistance exercise hardware, although these differences were not statistically significant. Absolute and relative preflight strength were moderately correlated (r = -0.47 and -0.54, respectively) with postflight strength changes. In-flight resistance exercise did not prevent decreased isokinetic strength after long-duration spaceflight. However, continued utilization of ARED, a more robust resistance exercise device providing higher loads than iRED, may result in greater benefits as exercise prescriptions are optimized. With reconditioning upon return to Earth, strength is largely recovered within 30 d.

Isokinetic Strength Responses to Season-long Training and Competition in Turkish Elite Soccer Players

There are not enough studies that describe the isokinetic strength of professional soccer players at high angular velocities. The purpose of this study was to evaluate the seasonal changes in isokinetic strength of Turkish professional soccer players (n=14) over the course of a 24-week soccer season. The isokinetic strength of players who underwent usual soccer training and weekly competition throughout the soccer season was assessed by means of the Biodex System 3 dynamometer with the knee attachment. The peak torque of knee extensor and flexor muscles were measured at angular velocities of 60°/s, 300°/s and 500°/s. Players were tested at the beginning and end of the competitive season. While the first- and second-test measurements did not show significant changes at 60°/s and 300°/s angular velocities, at the end of the training period, players’ knee strength changed significantly at 500°/s angular velocities. In addition, the H/Q ratio improved significantly for the dominant as well as non-dominant leg at 500°/s. Significant bilateral strength improvements for knee flexors were also observed at 500°/s. The findings of this study suggest that usual daily soccer training (technical, tactical, power, strength, endurance, flexibility, etc.) and weekly competition might produce changes in knee strength at high angular velocities.

Muscle Volume, Strength, Endurance, and Exercise Loads During 6-Month Missions in Space

Decrements in muscular strength during long-duration missions in space could be mission-critical during construction and exploration activities. The purpose of this study was to quantify changes in muscle volume, strength, and endurance of crewmembers on the International Space Station (ISS) in the context of new measurements of loading during exercise countermeasures. Strength and muscle volumes were measured from four male ISS crewmembers (49.5 +/- 4.7 yr, 179.3 +/- 7.1 cm, 85.2 +/- 10.4 kg) before and after long-duration spaceflight (181 +/- 15 d). Preflight and in-flight measurements of forces between foot and shoe allowed comparisons of loading from 1-g exercise and exercise countermeasures on ISS. Muscle volume change was greater in the calf (-10 to 16%) than the thigh (-4% to -7%), but there was no change in the upper arm (+0.4 to -0.8%). Isometric and isokinetic strength changes at the knee (range -10.4 to -24.1%), ankle (range -4 to -22.3%), and elbow (range -7.5 to -16.7%) were observed. Although there was an overall postflight decline in total work (-14%) during the endurance test, an increase in postflight resistance to fatigue was observed. The peak in-shoe forces during running and cycling on ISS were approximately 46% and 50% lower compared to 1-g values. Muscle volume and strength were decreased in the lower extremities of crewmembers during long-duration spaceflight on ISS despite the use of exercise countermeasures. in-flight countermeasures were insufficient to replicate the daily mechanical loading experienced by the crewmembers before flight. Future exercise protocols need careful assessment both in terms of intensity and duration to maximize the "dose" of exercise and to increase loads compared to the measured levels.

레슬링 선수들의 단기간 체중감량이 슬관절의 등속성 운동능력에 미치는 영향

본 연구는 고교 레슬링선수들의 단기간 체중감량에 따른 등속성 운동능력 중 다리의 peak torque, peak torque %BW, total work, total work %BW, endurance ratio에 대한 변화를 알아보기 위하여 자기 체중에서 체중감량이 없는 집단 7명, 5%이상 감량집단 7명을 대상으로 체중감량 전ㆍ후를 측정하여 얻은 결론은 다음과 같다. 1. Peak Torque의 변화. 굴근의 경우 5%이상 감량 집단의 <TEX>$60^{\circ}C$</TEX>sec, <TEX>$90^{\circ}C$</TEX>/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 <TEX>$60^{\circ}C$</TEX>/sec, <TEX>$90^{\circ}C$</TEX>/sec, <TEX>$250^{\circ}C$</TEX>/sec에서 모두 유의하게 감소하였다. 2. Peak Torque %BW의 변화. 굴근의 경우 5%이상 감량 집단의 60<TEX>$^{\circ}$</TEX>/sec, 90<TEX>$^{\circ}$</TEX>/sec, <TEX>$150^{\circ}C$</TEX>/sec에서 모두 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 <TEX>$90^{\circ}C$</TEX>/sec와 <TEX>$250^{\circ}C$</TEX>/sec에서 유의하게 감소하였다. 3. Total Work의 변화. 굴근의 경우 5%이상 감량 집단의 <TEX>$60^{\circ}C$</TEX>/sec,<TEX>$90^{\circ}C$</TEX>/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량집단의 <TEX>$50^{\circ}C$</TEX>/sec, <TEX>$90^{\circ}C$</TEX>/sec. <TEX>$250^{\circ}C$</TEX>/sec에서 모두 유의하게 감소하였다. 4. Total work %BW의 변화. 굴근의 경우 5%이상 감량 집단의 <TEX>$60^{\circ}C$</TEX>/sec, <TEX>$90^{\circ}C$</TEX>/sec, <TEX>$250^{\circ}C$</TEX>/sec에서 유의하게 감소하였다. 그리고 신근의 경우 5%이상 감량 집단의 <TEX>$50^{\circ}C$</TEX>/sec, <TEX>$90^{\circ}C$</TEX>/sec, <TEX>$250^{\circ}C$</TEX>/sec에서 모두 유의하게 감소하였다. 5. Endurance Ratio의 변화. 굴근과 신근의 경우 두 집단 모두 유의한 차이가 없었다. 단기간의 무리한 체중감량은 근력, 근지구력의 저하로 경기력을 저하시킬 뿐만 아니라 건강을 해칠 우려가 있기 때문에 단기간의 무리한 감량이 되지 않도록 과학적이고 체계적인 체중관리가 이루어져야 할 것으로 사료된다. The purpose of this study is to investigate isokinetic strength changes of knee joint in accordance with short-term weight loss of wrestlers. For this purpose, 14 male wrestlers of a K technical high school in B city participated in our research. The wrestlers were divided into two groups; one group of the wrestlers didn't lose any weight, and the other lost over 5% of their weights. The isokinetic strength was also observed before and after weight loss. The isokinetic strenght test were processed at test speed of the<TEX>$60^{\circ}C$</TEX>/sec, <TEX>$90^{\circ}C$</TEX>/sec, and <TEX>$250^{\circ}C$</TEX>/sec with the CYBEX NORM system(Cybex 770＋TMS, USA). Peak torque, peak torque %BW, total work, total work %BW, and endurance ratio were measured. Results showed that the isokinetic strength after the short-term weight loss of wrestlers decreased meaningfully Although endurance ratio didn't show any meaningful difference in our research, but more accurate research may find out the relationship between short-term weight loss and the endurance ratio of isokinetic strength.

The Effect of Different Electro-Motor Stimulation Training Intensities on Strength Improvement

The effect of different training intensities of electro-motor stimulation (EMS) on strength gains produced in the quadriceps femoris muscle group was investigated. Twenty-four subjects were randomly assigned to one of three groups: Control (C), Low Intensity (LI) trained at 25% of their maximum voluntary isometric contraction (MVIC), and High Intensity (HI) trained at 50% of MVIC. Results indicated a significant strength improvement in both training groups (p<0.01) following a three-week EMS training program. The HI group showed significantly greater strength gains (48.5%) than the LI group (24.2%) (p<0.01). A significant carry-over effect was also demonstrated in a three-week follow-up period, specifically in the HI group. Positive isokinetic strength changes in the concentric mode were observed in both training groups. In addition, a significant cross transfer effect was demonstrated in the contralateral homologous muscle group (p<0.01) for both HI and LI groups.