Isokinetics and Exercise Science - Volume 30, issue 1

Authors: Jung, Eunjoo | Sung, Jinwook | Uh, Injoon | Oh, Jaeseop

Article Type: Research Article

Abstract: BACKGROUND: Active straight leg-raise (ASLR) is often performed to strengthen abdominal muscles. The correct execution and maximum benefit of the ASLR can be achieved using abdominal hollowing (AH) and abdominal bracing (AB) exercises. OBJECTIVE: To compare the effects of AH and AB on transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) thicknesses, as well as on the pelvic rotation angle, in healthy women during active ASLR. METHODS: The participants in this study were assigned randomly to either the AH (n = 15) or AB groups (n …= 15). During ASLR, abdominal muscle thickness was measured using ultrasound and pelvic rotation was measured using a Smart KEMA device. Each trial was repeated three times for 5 s each. RESULTS: The thickness of the TrA was significantly greater during ASLR with AH than during ASLR with AB (p < 0.001). In contrast, there was no respective significant change in the thickness of the EO (p > 0.311) or IO (p > 0.818). Pelvic rotation angle was significantly reduced during ASLR with AB, compared with ASLR with AH (p < 0.018). CONCLUSIONS: We recommend that AH be performed for the selective contraction of TrA during ASLR, and that AB be performed for the prevention of the pelvic rotation during ASLR. Therefore, AH and AB should be separately done in stabilization exercises. Show more

Keywords: Abdominal hollowing, abdominal bracing, abdominal muscle thickness, pelvic rotation angle

DOI: 10.3233/IES-203204

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 1-6, 2022

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

Article Type: Research Article

Abstract: BACKGROUND: Knee strength weakness is a major problem frequently observed in patients during postoperative rehabilitation following anterior cruciate ligament reconstruction (ACLR). OBJECTIVE: To investigate whether knee strength normalized to muscle volume could better detect side-to-side differences than that normalized to body weight following ACLR. METHOD: This study included 17 patients who had undergone primary ACLR (11.6 ± 2.3 months). Body weight and total muscle volume were measured using a bioelectrical impedance analysis composition scale. Isokinetic knee extension and flexion moment were measured at 60 ∘ /s and …180 ∘ /s, respectively. Bivariate correlation analysis was used to examine correlations between body composition and knee strength. Differences in knee strength between the operated and unoperated legs were analyzed using a paired t -test, which calculated the effect size. RESULTS: There was a significant correlation between knee strength and body weight (r = 0.53–0.67); however, a stronger correlation was observed between knee strength and total muscle volume (ρ = 0.80–0.87). The effect size was larger for knee strength expressed as % total muscle volume than for knee strength expressed as % body weight. CONCLUSION: Strength expressed as % total muscle volume may be more accurate than that expressed as % body weight for detecting side-to-side differences in knee strength following ACLR. Show more

Keywords: ACL reconstruction, isokinetic moment, isokinetic strength, muscle mass

DOI: 10.3233/IES-210132

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 7-13, 2022

Authors: Cuña-Carrera, Iria Da | Alonso-Calvete, Alejandra | González-González, Yoana | Soto-González, Mercedes

Article Type: Research Article

Abstract: BACKGROUND: The underlying morphology and behavior of abdominal muscles during breathing are still lacking in knowledge in healthy population. OBJECTIVE: To analyze the effects of three different types of breathing on the architectural characteristics of abdominal muscles. METHODS: Ninety-eight healthy subjects were measured to assess the effects of breathing on the abdominal muscles, subjects performed three different types of breathing and the muscular thickness was measured with ultrasound imaging, analyzing also the differences between sexes. RESULTS: During the three different types of breathing and in comparison with the resting state, …an increase of the thickness has been reported in the transversus abdominis (p < 0.001; effect size = 2.44, very large) and internal oblique (p < 0.001; effect size = 1.04, moderate) in both sexes, but with a higher increase in men. External oblique and rectus abdominis increased their thickness through breathing only while the lips were with pursed (p < 0.05) with trivial effect sizes and only differences between sexes were found in rectus abdominis. CONCLUSIONS: All breathings activated the deepest abdominal muscles, but the most superficial were only activated with lips pursed. Moreover, men appeared to activate more the deepest abdominal muscles but also the rectus abdominis. Findings in this study support the use of different types of breathing depending on the muscle to be activated or the sex, helping health care professionals to address their interventions on the abdominal muscles with a more focused approach. Show more

Keywords: Ultrasonography, abdomen, breath test, biomechanics

DOI: 10.3233/IES-210159

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 15-21, 2022

Authors: dos Santos, Marcel Lopes | Mann, James Bryan | Lockie, Robert George | Berton, Ricardo | Jacobson, Bert Hans | Dawes, James Jay

Article Type: Research Article

Abstract: BACKGROUND: Bar velocity has been proved to accurately predict performance in several exercises. OBJECTIVE: To estimate the total number of repetitions during the NFL-225 Bench Press Test (NFL-225) based on bar velocity in collegiate football players. METHODS: Forty-six NCAA Division I football players performed as many bench press repetitions as possible with a standard load of 225 lbs. The variables used to estimate the total number of repetitions were: mean velocity of the fastest repetition achieved in the test (FR); mean velocity of the first repetition (V1); mean velocity of the first three …repetitions (MV3); mean velocity of the first five repetitions (MV5); and mean velocity of the first 10 repetitions (MV10). Linear regression analyses were conducted to predict NFL-225 performance based on bar velocity. RESULTS: The prediction of the total number of repetitions was similar between the five mean velocities (FR: R 2 = 0.64, SEE = 3.87, V1: R 2 = 0.65, SEE = 3.80, MV3: R 2 = 0.70, SEE = 3.52, MV5: R 2 = 0.71, SEE = 3.48, and MV10: R 2 = 0.62, SEE = 3.37). CONCLUSION: The mean velocities allowed the production of general regression equations for the estimation of the total number of repetitions in the NFL-225. V1 and MV3 presented as the best options due to their accuracy, time-efficiency, and reduced musculoskeletal stress. Show more

Keywords: Velocity-based training, muscular endurance, American Football, NFL Combine

DOI: 10.3233/IES-210147

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 23-28, 2022

Authors: Ojeda-Aravena, Alex | Herrera-Valenzuela, Tomás | Valdés-Badilla, Pablo | Azócar-Gallardo, Jairo | Campos-Uribe, Victor | García-García, José Manuel

Article Type: Research Article

Abstract: BACKGROUND: Explosive strength and change of direction speed (CODS) are relevant physical abilities in karate. OBJECTIVE: To examine the relationship between the characteristics of explosive strength and the 5-m linear sprint (5M) with CODS performance and ii) to examine the influential characteristics of explosive strength on CODS performance. METHODS: Eighteen cadet and junior karate athletes, eight females and ten males were evaluated. The physical abilities assessments included: squat jump (SJ), countermovement jump (CMJ), 5M and CODS. Also, pre-stretch percentage increase (PSA), eccentric utilization index (EUR) reactive strength index (RSI) were calculated. …RESULTS: Superior performance (p < 0.05) was documented in SJ, CMJ and CODS in male vs. female. Also, significant correlations between CODS with SJ and CMJ (r = - 0.70 to - 0.80; R 2 = - 0.51 to - 0.73; p < 0.05, respectively) and correlations (r = - 0.14 to - 0.22; R 2 = 0.01 to 0.04; p > 0.05) between CODS with RSI, EUR and PSA. Multiple regression model documented that only SJ significantly influenced CODS performance in male (R 2 = 60%; p = 0.009) and female (R 2 = 71%; p = 0.001). CONCLUSION: CODS correlate with SJ and CMJ. In particular, SJ influence CODS independently of gender. Show more

Keywords: Combat sports, martial arts, athletic performance, muscle strength, motion perception

DOI: 10.3233/IES-210114

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 29-38, 2022

Authors: Iguchi, Junta | Matsunami, Minoru | Hojo, Tatsuya | Fujisawa, Yoshihiko | Kuzuhara, Kenji | Yuasa, Yasuhiro | Kitazawa, Toshiya

Article Type: Research Article

Abstract: BACKGROUND: Few studies have investigated the variations in body composition and performance in Japanese collegiate American-football players. OBJECTIVE: To clarify what characterizes competitors at the highest levels – in the top division or on the starting lineup – we compared players’ body compositions and performance test results. METHODS: This study included 172 players. Each player’s body composition and performance (one-repetition maximum bench press, one-repetition maximum back squat, and vertical jump height) were measured; power was estimated from vertical jump height and body weight. Players were compared according to status (starter vs. non-starter), position (skill vs. …linemen), and division (1 vs. 2). Regression analysis was performed to determine characteristics for being a starter. RESULTS: Players in higher divisions and who were starters were stronger and had more power, greater body size, and better performance test results. Players in skill positions were relatively stronger than those in linemen positions. Vertical jump height was a significant predictor of being a starter in Division 1. CONCLUSION: Power and vertical jump may be a deciding factor for playing as a starter or in a higher division. Show more

Keywords: American football, performance test, body composition, muscular strength, power

DOI: 10.3233/IES-200222

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 39-46, 2022

Authors: Jo, Young Jin | Kim, Young Kyun

Article Type: Research Article

Abstract: BACKGROUND: Dynamic knee valgus (DKV) is a known risk factor for acute and chronic knee injuries and is more frequently diagnosed in females. A real-time single-leg squat test (SLST) could screen for DKV to prevent injuries. OBJECTIVE: To compare the differences in lower extremity strength and range of motion (ROM) in female soccer athletes with and without DKV during an SLST. METHODS: Eighteen subjects with DKV (DKV group) and 18 subjects without DKV (control group) during a single-leg squat were included. Hip strength (flexion, extension, abduction, adduction, internal rotation, and external rotation) was …measured with a hand-held dynamometer. Hip ROM (internal and external rotation), and ankle ROM (dorsiflexion with the knee flexed and extended) were measured. Independent t-test was used to compare the averages of the groups. RESULTS: There were significant differences in hip abduction to adduction strength ratio (DKV: 1.48 ± 0.3, control: 1.22 ± 0.26, p < 0.01) and ankle dorsiflexion with knee flexed (DKV: 17.22 ± 6.82, control: 21.22 ± 4.55, p < 0.05) and extended (DKV: 10.14 ± 4.23, control: 14.75 ± 3.40, p < 0.001) between the groups. CONCLUSION: The hip abduction to adduction strength ratio and gastrocnemius and soleus flexibility may be associated factors in dynamic knee valgus and therefore should be assessed and treated, if indicated, as a possible preventive measure in female athletes with this variation. Show more

Keywords: Single-leg squat test, dynamic knee valgus, female, soccer

DOI: 10.3233/IES-200260

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 47-52, 2022

Authors: Misjuk, Mikola | Rannama, Indrek

Article Type: Research Article

Abstract: BACKGROUND: Lower limb muscular asymmetry is not well studied and may have a negative impact on performance. OBJECTIVE: To estimate how muscular strength and strength asymmetry affect jumping performance in soccer players. METHODS: Twenty-eight male professional soccer players took part in the study. The countermovement jump (CMJ) without arm swing was used to determine jumping height. Muscle strength was measured concentrically at 60 and 300 ∘ /s. RESULTS: The peak moment of the knee extensors was positively and significantly correlated with the CMJ; r = …0.608 at 300 ∘ /s and r = 0.489 at 60 ∘ /s. The asymmetry of the knee flexors between the stronger and weaker leg was negatively and moderately correlated with the CMJ at 300 ∘ /s (r = - 0.396). The regression model (R 2 = 0.474) showed that an increase of 0.18-Nm/kg in the relative strength of the knee extensors at 300 ∘ /s (by one SD) was related to an increase of 3-cm in the CMJ. Reducing the asymmetry of the knee flexors by 6.8 percentage points (by one SD) was related to a rise of 1.7-cm in the CMJ. CONCLUSIONS: Greater strength in the knee extensors, preferably tested at higher velocity, and reduced asymmetry in the strength of the lower hamstring muscles have a statistically significant effect on the CMJ. Show more

Keywords: Local muscle strength, isokinetic testing, countermovement jump

DOI: 10.3233/IES-200240

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 53-60, 2022

Authors: Shen, Yupeng | Fu, Yanqing | Ge, Yu | Wen, Yuhong

Article Type: Research Article

Abstract: BACKGROUND: Lower-extremity muscle strength and ankle flexibility play key roles in underwater swimming movements. OBJECTIVES: To investigate the relationship between knee isokinetic strength and the speed of underwater dolphin kicks (UDK-S) in competitive male swimmers and identify whether ankle flexibility affects the association between knee isokinetic strength and UDK-S. METHODS: Fifty-two highly trained male swimmers participated in this study. The speed at which the participants travelled 15 m performing UDKs was calculated as UDK-S. Knee flexor and extensor concentric isokinetic strength at fast (240 ∘ /s) and slow (60 ∘ …/s) velocities and ankle flexibility were evaluated. Bayesian framework analysis was conducted to examine the relationship between these variables and determine whether this relationship is influenced by ankle flexibility. RESULTS: There was strong-to-extremely strong evidence (Bayes factor = 24.4 to 198.3) that knee extensor (60 ∘ /s) and knee flexor (60 ∘ /s and 240 ∘ /s) strength are positively and generally moderately correlated with UDK-S. Ankle plantar flexion flexibility was identified to be a moderator between knee extensor strength (60 ∘ /s) and UDK-S. CONCLUSIONS: Knee extensor and knee flexor strength were significantly correlated with UDK-S, and the relationship between knee muscle strength and UDK-S was influenced by ankle plantar flexion flexibility in male competitive swimmers. Show more

Keywords: Knee muscle strength, underwater dolphin kick, ankle flexibility, male, Bayesian approach

DOI: 10.3233/IES-200255

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 61-68, 2022

Authors: Ruan, Mianfang | Zhang, Qiang | Zhang, Xin | Hu, Jing | Wu, Xie

Article Type: Research Article

Abstract: BACKGROUND: It remains unclear if plyometric training as a single component could improve landing mechanics that are potentially associated with lower risk of ACL injury in the long term OBJECTIVE: The purpose of this study was to investigate the influence of experience undertaking plyometrics on landing biomechanics in female athletes. METHODS: Non-jumpers with little experience in plyometric training (12 female college swimmers) and jumpers with five years of experience in plyometric training (12 female college long jumpers and high jumpers) were recruited to participate in two testing sessions: an isokinetic muscle force test …for the dominant leg at 120 ∘ /s and a 40-cm drop landing test. An independent t test was applied to detect any significant effects between cohorts for selected muscle force, kinematic, kinetic, and electromyography variables. RESULTS: While female jumpers exhibited greater quadriceps eccentric strength (P = 0.013) and hamstring concentric strength (P = 0.023) during isokinetic testing than female swimmers, no significant differences were observed in kinematics, kinetics, and muscle activities during both drop landing and drop jumping. CONCLUSIONS: The results suggest that the female jumpers did not present any training-induced modification in landing mechanics regarding reducing injury risks compared with the swimmers. The current study revealed that plyometric training as a single component may not guarantee the development of low-risk landing mechanics for young female athletes. Show more

Keywords: ACL injury, jumping, drop landing, 3D analysis, plyometric training

DOI: 10.3233/IES-210149

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 69-78, 2022

Authors: Nitzsche, Nico | Siebert, Tobias | Schulz, Henry | Stutzig, Norman

Article Type: Research Article

Abstract: BACKGROUND: Reactive performance is an important component of rhythmic gymnastics. So far, it is unclear whether additional plyometric training in female gymnasts shows an increase in performance. OBJECTIVE: The aim of the study was to examine the effect of additional plyometric training in rhythmic gymnastics on the reactive jumping performance and strength of the lower leg muscles. METHODS: Fifteen rhythmic gymnasts (age: 12.3 ± 2.6 years, height: 1.47 ± 0.12 m, body weight: 37.3 ± 9.3 kg, BMI: 16.7 ± 2.1 …kg*m - 2 ; competition level: national and international championships, Tanner stages I–III) participated in the study. The athletes were assigned to an experimental (EG) and a control group (CG). The EG performed plyometric exercises three times per week in addition to the regular training. Before and after six weeks of training the reactive jump performance, the work of dorsi flexors and plantar flexors performed during isokinetic plantarflexion, as well as the performance in two sport-specific tests were measured. RESULTS: In contrast to the CG, in the EG the jump height (pre: 24.8; post: 27.25 cm; p < 0.05) and the reactive-strength-index (pre: 1.01; post: 1.19; p < 0.01) increased significantly. The EG achieved significant improvements in the counter movement jump test (pre: 27.0 cm; post: 31.5 cm; p < 0.01) and in the sport specific double rope jump test (jumps per minute, pre: 18.0; post: 23.0; p < 0.01). Furthermore, a significant increase in work performed during plantarflexion was found in the EG for the right leg (pre: 24.9 J; post: 29.7 J; p < 0.01) and a tendency to increase for the left leg (pre: 26.4 J; post: 37.7 J; p = 0.05). CONCLUSION: Both reactive strength and dynamic force can be efficiently increased by plyometric training. It may be recommended to include plyometric exercises in the training regime of rhythmic gymnasts. Show more

Keywords: Plyometric exercise, jumping, reactive strength, drop jump

DOI: 10.3233/IES-210148

Citation: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 79-87, 2022