Isokinetics and Exercise Science - Volume Pre-press, issue Pre-press

Authors: Konieczny, Mariusz | Pakosz, Paweł | Domaszewski, Przemysław | Skorupska, Elżbieta

Article Type: Research Article

Abstract: BACKGROUND: In short track speed skating, there is asymmetric fatigue of the gluteus maximus (GM) muscle resulting from the technique of skating. Scientific reports confirm the relationship between muscle fatigue and its change in the slope frequency of bioelectrical activity. OBJECTIVE: To investigate whether athletic experience in elite short track speed skating can distinguish the asymmetry change in slope frequency of the raw electromyographic signal (EMG) of the GM muscle, influenced by the disparity in experience between junior and senior athletes. METHODS: In the research, an elite group of short track speed …skating national team athletes Junior and Senior, participated. Isometric tension GM muscle was tested using the Biering-Sorensen test. RESULTS: The study confirmed differences in the asymmetry of slope frequences EMG signal in GM muscle between juniors and seniors in short track speed skating (p ⩽ 0.001). Senior athletes showed greater slope frequences in the right GM muscle (p ⩽ 0.002), while juniors showed greater in the left GM muscle (p ⩽ 0.008). Intergroup analysis revealed significantly meaningful differences (p ⩽ 0.001) in the level of slope frequences of the right GM muscle (juniors vs. seniors), highlighting the asymmetry resulting from experience. CONCLUSIONS: Statistically significant differences in the level of slope frequences of the right gluteus maximus muscle juniors vs. seniors were demonstrated, suggesting asymmetry due to experience and skating technique. Show more

Keywords: Electromyography, fatigue, sports technique, overload, junior vs senior

DOI: 10.3233/IES-240004

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-6, 2024

Authors: Stotz, Andreas | Richter, Steven | Mason, Joel | Zech, Astrid

Article Type: Research Article

Abstract: BACKGROUND: It has been demonstrated that maximum isometric muscle moment can surpass maximum eccentric muscle moment at individually adjusted joint angles in men. However, no information about these muscle mechanics is available for women. OBJECTIVE: To examine the maximum muscle moment hierarchy with equal conditions in women. METHODS: Maximum voluntary concentric, eccentric, and isometric muscle moments of ankle, knee, and hip flexors and extensors as well as hip adductors and abductors were tested in eighteen young women. The sequence of muscle group testing was the same for all subjects, and the sequence of …contraction types was randomized. All dynamic contractions were performed at 60∘ /s. Peak moment angle of concentric contractions was applied for isometric moment testing. A repeated measures ANOVA with posthoc Bonferroni correction was used to compare means between contraction types. RESULTS: Differences in maximum moment mean values between the three contraction types were apparent for all muscle groups (p < 0.001). Concentric muscle moment was significantly the weakest contraction type. Eccentric contractions generated significantly higher moments than isometric contractions in dorsiflexion, plantarflexion, knee flexion, and hip adduction. CONCLUSION: Significant differences in maximum lower body muscle moments exist between concentric, eccentric, and isometric contractions in women. Compared to previous research for men there appears to be a sex-specific contraction type hierarchy with women exhibiting superior ability to generate higher eccentric muscle moment relative to other contraction types. These results should be considered when designing contractiontype specific intervention programs. Show more

Keywords: Isokinetic, isometric, sex-differences, joint angle, maximum muscle torque

DOI: 10.3233/IES-240031

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-9, 2024

Authors: Oh, Seokjong | Kim, Yonghwan | Han, Joungkyue

Article Type: Research Article

Abstract: BACKGROUND: The gluteus medius (GM) plays an important role in stabilizing the knee and preventing injury. OBJECTIVE: This study aimed to determine the immediate effects of weight-bearing gluteus medius exercises on lower-extremity muscle function and dynamic knee valgus. METHODS: Eighteen healthy adults (nine each of both sexes) performed three types of weight-bearing gluteus medius exercises (standing, mini-squat, and dead-lift), and a range of kinematic variables were tested in triplicate. Weight-supporting GM exercise consisted of three sets of 15 repetitions of the lateral band walk. The Y-balance test (YBT) and vertical single-leg jump were …used as indicators of muscle function in the lower limbs. We used a video analyzer to film the dynamic knee valgus and performed a YBT for the supporting leg and landing leg following a jump. RESULTS: The height of the single-leg vertical jump and the posterolateral and total YBT scores were significantly higher in the dead-lift posture than in the standing and mini-squat postures. Motion analysis of the dead-lifts revealed high hip flexion on the supporting leg in the posterolateral direction, as determined by the YBT, with low levels of internal hip rotation on the landing leg during the one-leg vertical jump. CONCLUSION: As an immediate effect of gluteus medius exercise, the dead-lift posture facilitated single-leg vertical jump, posterolateral balance, and reduced dynamic knee valgus. Show more

Keywords: Gluteus medius, dead-lift, dynamic knee valgus, muscle function, dynamic balance

DOI: 10.3233/IES-240045

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-12, 2024

Authors: Yu, Il-Young | Ma, Rui | Kim, Tae-Gyu

Article Type: Research Article

Abstract: BACKGROUND: In overhead athletes, including adolescent baseball players, scapular dyskinesis is linked to rotator cuff muscle weakness. This relationship exists because the scapula provides a stable platform and maintains the optimal length – tension relationship essential for maximal rotator cuff muscle force. While the link between scapular dyskinesis and the isometric strength of the rotator cuff has been studied, the connection with dynamic strength, particularly isokinetic concentric and eccentric strength, and their effects on functional strength ratios (agonist concentric strength to antagonist eccentric strength ratio), remain less clear. OBJECTIVES: This study aimed to explore the association between …scapular dyskinesis and the isokinetic concentric and eccentric strength of the rotator cuff muscles, functional strength ratios, and shoulder function, as well as to determine the differences in these parameters between the dominant shoulder with scapular dyskinesis and the non-dominant shoulder without dyskinesis in adolescent baseball players. METHODS: This study included 50 adolescent baseball players with scapular dyskinesis. Measurements included scapular movement patterns in the scapular dyskinesis test, scapular dyskinesis scores, isokinetic concentric and eccentric internal and external rotation torques (expressed as peak torque/body weight, %), functional strength ratios, and shoulder function. Correlations between scapular dyskinesis scores and various strength and functional measurements were analyzed, as well as differences between the dominant and non-dominant shoulders using the paired t -test. RESULTS: Internal and external rotation torques were reduced on the scapular dyskinesis side across all types of contractions. A weak negative correlation was observed between the scapular dyskinesis score and eccentric internal rotation torque, with no significant correlations seen for the other variables. A moderate negative correlation was found between concentric internal rotation torque and the eccentric external rotation/concentric internal rotation ratio. Additionally, concentric and eccentric external rotation torques showed a weak negative and a positive correlation with the eccentric internal rotation/concentric external rotation ratio, respectively. CONCLUSIONS: Reduced isokinetic strength was noted on the scapular dyskinesis side, correlating particularly with eccentric internal rotation torque. This study highlights the relationship between rotator cuff muscle strength and functional strength ratios, suggesting the need for targeted strategies to restore balance between scapular positioning and rotator cuff strength. Show more

Keywords: Scapular dyskinesis, rotator cuff muscle strength, functional strength ratio, adolescent baseball players

DOI: 10.3233/IES-240018

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-9, 2024

Authors: Lim, Wootaek

Article Type: Research Article

Abstract: BACKGROUND: Warm-up exercises are often recommended to enhance flexibility, reduce the risk of injury, and improve performance. However, the optimal number of warm-up repetitions remains unclear. Additionally, the previously suggested sit-and-reach test may not be suitable for efficiently stimulating the target muscles. OBJECTIVE: This study investigated the effects of a warm-up consisting of 15 straight leg raise (SLR) repetitions on hip and knee flexibility by comparing individuals with and without hamstring tightness (HT and NoHT, respectively). METHODS: Thirty healthy adults were classified as having HT or NoHT based on their SLR angle before warm-up. …The participants performed 15 repetitions of the SLR as warm-up, followed by hip and knee flexibility tests. RESULTS: Warm-ups significantly improved hip and knee flexibility in both HT and NoHT groups. Improvements in flexibility were not significantly different between groups. The most notable increase in flexibility was observed between the sixth and ninth SLR trials. CONCLUSIONS: The clinical utility of a warm-up consisting of 15 SLR repetitions is supported by this study, as a substantial increase in hip flexibility was observed in all participants regardless of HT. In clinical settings, a maximum of 10 repetitions may be sufficient to achieve optimal results. Show more

Keywords: Joint flexibility, muscle tightness, range of motion, warm-up exercise

DOI: 10.3233/IES-240049

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-7, 2024

Authors: Özbay, Serhat | Gençoğlu, Cebrail | Ulupınar, Süleyman | Çınar, Vedat | Ouergui, Ibrahim | Hölbling, Dominik

Article Type: Research Article

Abstract: BACKGROUND: Based on recent research, slight performance differences, particularly dependent on the state of recovery, might be crucial for tournament success among elite-caliber kickboxers. OBJECTIVE: This study aims to; a) determine which strength-power tests could discriminate better between elite and top-elite kickboxers and, b) to evaluate changes in testing results between fatigued and well-rested athletes. METHODS: Twenty-two international kickboxers (including World and European Champions) volunteered to participate in this study. Nine kickboxers were assigned to the top-elite group and 13 to the elite group based on their highest tournament achievements. Subjects performed the …Wingate test (Win) for anaerobic power; countermovement jump (CMJ) and squat jump (SJ) for neuromuscular power; push-ups and pull-ups for strength endurance; squats (SQ) and bench press (BP) for maximal dynamic strength; handgrip, leg, and back strength for isometric strength after full rest, following the fatigue and advanced fatigue protocols. RESULTS: Discriminant function analysis correctly classified the groups at 60.5%, 75.3%, and 86.3% in the resting, fatigue, and advanced fatigue protocols, respectively. Furthermore, all strength-power performances have significantly decreased and lactatepeak increased (p < 0.05) after the fatigue and advanced fatigue protocols in both groups. Significant interaction were also observed in the Winpeak (p < 0.001, η p 2 = 0.559), Winmean (p = 0.009, η p 2 = 0.246), CMJ (p = 0.010, η p 2 = 0.273), push-ups (p < 0.001, η p 2 = 0.389), SQabsolute (p = 0.001, η p 2 = 0.337), BPabsolute (p = 0.014, η p 2 = 0.235) and, Lactatepeak (p = 0.026, η p 2 = 0.220). CONCLUSION: Resistance to fatigue may be the key component for distinguishing elite-level athletes. Thus, strength-power tests should be performed following a certain level of fatigue for the elite athletes due to distinguish them more effectively. Show more

Keywords: Kickboxing, strength-power tests, strength performance, performance decrease, Wingate

DOI: 10.3233/IES-240023

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-12, 2024

Authors: Mochizuki, Yukina | Naito, Takuto | Kikuchi, Sayaka | Homma, Hiroki | Almeida, Kathleen Yasmin de | Kikuchi, Naoki

Article Type: Research Article

Abstract: BACKGROUND: The evidence of response to velocity loss cut-off training with similar total repetitions are limited. OBJECTIVE: This study aimed to examine the effects of different velocity loss training protocols after 3 weeks of traditional resistance training protocols on strength and power in trained men. METHODS: Twenty highly trained men participated in the study. The protocols were performed twice a week for 6-weeks, with the first 3-weeks consisting of traditional (TR) training protocols and the other 3-weeks of velocity loss (VL) training protocols. The TR and VL training protocols consisted of 80% 1RM …of full squat exercise with 4-min rest intervals. The participants were randomly assigned to two different protocols during the VL training protocols, each with different velocity loss within sets (V20%; n = 10 or VL40%; n = 10). The number of sets was adjusted so that the total number of repetitions for each VL was similar (VL20 × 3 sets, VL40 × 2 sets). Measurements assessed using one-repetition maximum (1RM), isokinetic strength, 20 m-sprint (T20), and counter movement jump (CMJ). RESULTS: The total number of repetitions in the session significantly decreased from the TR training protocol to the VL training protocol in each group (TR to VL20; - 18%, TR to VL40; - 27%, p < 0.05). There was no significant difference of repetitions between groups. The T20 and isokinetic strength changed significantly in both groups after 6-weeks of training. CONCLUSION: The VL training protocol with reduced volume following the TR training protocol has been shown to maintain and increase strength and power outcomes. However, no significant difference in training response was observed between VL20 and VL40 protocols. The combination of TR and VL protocols might be an effective strategy for optimizing athletic performance. Show more

Keywords: Resistance training, velocity loss, velocity-based training, training volume

DOI: 10.3233/IES-240013

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-9, 2024

Authors: Ko, Byung-Woo | Bae, Young-Hyeon | Yoon, Bum Chul | Shin, Joon-Ho

Article Type: Research Article

Abstract: BACKGROUND: A passive-control foot press trainer (PFPT) based on spring resistance aims to strengthen the ankle joint, similar to heel raise exercise (HRE). OBJECTIVE: To compare the muscle activity of the tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis, rectus femoris, and biceps femoris between PFPT and HRE. METHODS: Eight healthy women performed four exercise conditions: PFPT forefoot (PFPT FF), PFPT rearfoot (PFPT RF), HRE at the floor level (HRE F), and HRE on the block (HRE B). During exercise, muscle activity was measured using surface electromyography and subsequently converted to percentages of maximum voluntary …isometric contraction. RESULTS: Tibialis anterior showed the highest activity in PFPT FF, with significant difference from other conditions. Gastrocnemius medialis and lateralis demonstrated the highest activity in HRE B; Rectus femoris showed the highest activity in PFPT RF, showing significant differences from other conditions (p < 0.05). Biceps femoris exhibited the highest activity in HRE F and a significant difference from PFPT FF and PFPT RF. CONCLUSIONS: Lower leg and thigh muscle activity between PFPT and HRE had similarities and differences. Future studies should analyze the long-term effects of PFPT, including on patients with musculoskeletal and nervous system injuries. Show more

Keywords: Passive-control foot press trainer, heel raise exercise, ankle exercise, electromyography, muscle activity, muscle strength

DOI: 10.3233/IES-230157

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-10, 2024

Authors: Ohji, Shunsuke | Aizawa, Junya | Hirohata, Kenji | Ohmi, Takehiro | Mitomo, Sho | Koga, Hideyuki | Yagishita, Kazuyoshi

Article Type: Research Article

Abstract: BACKGROUND: Recovery of the isokinetic knee extensor strength on the operated side following anterior cruciate ligament (ACL) reconstruction is commonly calculated as a ratio with the value from the non-operated side serving as the denominator. However, the validity of the values of the non-operated side remains unclear. OBJECTIVE: This study aimed to determine the relationship between whole-body muscle mass and non-operated knee extensor strength after ACL reconstruction. METHODS: In 27 patients who underwent ACL reconstruction, muscle mass was measured using bioelectrical impedance analysis, and bilateral concentric knee extensor strength was measured using an …isokinetic dynamometer at angular velocities of 60∘ /s and 180∘ /s. Correlation and single regression analyses were performed to examine the relationship between whole-body muscle mass and knee extensor strength. RESULTS: There was a strong to very strong positive association between whole-body muscle mass and non-operated knee extensor strength (60∘ /s: r = 0.85, 180∘ /s: r = 0.90, P < 0.01). Univariate regression analysis showed that whole-body muscle mass was a strong predictor of non-operated knee extensor strength (R2 = 0.71–0.81). CONCLUSIONS: Assessing both whole-body muscle mass and knee extensor strength may be used to determine whether muscle strength on the non-operated side is appropriate for the individual’s body composition. Show more

Keywords: ACL repair, ACLR, isokinetic strength, extension torque, muscle volume

DOI: 10.3233/IES-240011

Citation: Isokinetics and Exercise Science, vol. Pre-press, no. Pre-press, pp. 1-10, 2024