Isokinetics and Exercise Science - Volume 29, issue 2
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Isokinetics and Exercise Science (IES) is an international journal devoted to the study of theoretical and applied aspects of human muscle performance. Since isokinetic dynamometry constitutes the major tool in this area, the journal takes a particular interest in exploring the considerable potential of this technology.
Isokinetics and Exercise Science publishes studies associated with the methodology of muscle performance especially with respect to the issues of reproducibility and validity of testing, description of normal and pathological mechanical parameters which are derivable from muscle testing, applications in basic research topics such as motor learning paradigms and electromyography. The journal also publishes studies on applications in clinical settings and technical aspects of the various measurement systems employed in human muscle performance research.
Isokinetics and Exercise Science welcomes submissions in the form of research papers, reviews, case studies and technical reports from professionals in the fields of sports medicine, orthopaedic and neurological rehabilitation and exercise physiology.
Abstract: BACKGROUND: Data about lower extremities’ strength and power asymmetries in fencers, and their relationships to fencing performance are limited and inconsistent. OBJECTIVE: The aim of the present study was to investigate asymmetries, between dominant (D) and non-dom (ND) legs of elite young male and female fencers, in relation to performance in fencing specific tests. METHODS: Anthropometric characteristics, unilateral vertical-horizontal jumping, isokinetic strength, lunge and step lunge performances were evaluated in 16 male and 22 female elite fencers. RESULTS: Significant differences between genders were found for all anthropometric measurements (p <…0.05). No significant bilateral asymmetries and gender x laterality effects were observed (p > 0.05). Fencing performance was negatively correlated with the D leg’s flexion/extension (F/E) ratio at 300 ∘ /s (r: - 0.564 to - 0.619, p < 0.05). In addition, D leg’s F/E ratio at 300 ∘ /s was positively related to lung peak velocity and power in female fencers (r: 0.562–0.649; p < 0.05). Finally, only in female fencers, unilateral triple hop distance was significantly related to lung peak velocity and power (r: 0.442–0.500; p < 0.05). CONCLUSIONS: The results of the present study suggest that the differential activation/movement pattern of the D and ND leg muscles do not lead to anatomical, dynamic and functional lower extremities asymmetries.
Abstract: BACKGROUND: Sprinting at the start of a BMX race is considered one of the most important determinants of performance. Therefore, different devices and technologies have been developed to improve this ability to sprint, such as non-circular CR (CR) systems. OBJECTIVE: To compare new pedalling performance determinants for the first meters of the acceleration phase in BMX, with two different CR systems, circular and non-circular, in Elite abd Cadet cyclists. METHODS: Two level of BMX cyclists of the Spanish national team – Elite (n = 7), and Cadet (n…= 7) – performed two sprints with different CR conditions (circular and non-circular). Each condition was performed in ecological BMX race conditions. Total distance (m), reaction time (s), power output (W) and the ratio between the powers of 90 and 270 ∘ (local extrema) and the powers at 0 and 180 ∘ (dead centres) of the pedalling (%PM) were analysed. RESULTS: In Elite group, no differences were found between circular and non-circular CR in total distance, reaction time, and %PM. In the Cadet group, differences were found between circular and non-circular CR conditions in %PM (p = 0.02), resulting in better results for the circular CR. In addition, no differences in total distance and reaction time were found. CONCLUSIONS: The use of non-circular CR system does not result in performance improvement in either Elite or Cadet cyclists.
Abstract: BACKGROUND: The 20-maximum trampoline jump test is a commonly used performance measure in competitive trampoline gymnastics. However, its reliability and characteristics are poorly understood. OBJECTIVE: To determine the reliability of the 20-maximum trampoline jump test and describe its characteristics. METHODS: Thirty-two national and international level trampoline gymnasts (18 ± 5 years) performed two, 20-maximal straight jump tests, separated by 24–72 hours. Time of flight (total, jumps 1–10 and jumps 11–20), force (average and peak), horizontal displacement and contact time were measured by a competition standard system. Test-retest reliability was assessed…using intraclass correlation coefficient (ICC), typical error, and coefficient of variation (CV). RESULTS: Total time of flight significantly decreased between trial 1 (31.80 ± 1.98 s) and trial 2 (31.43 ± 1.99 s; p < 0.05), however test-retest reliability was excellent (ICC = 0.96, CV = 1.3%). Other time of flight and force measures significantly decreased from trial 1 to trial 2, whereas contact time increased. All secondary measures displayed very high ICC (0.95–0.99) and low CV values (0.5–1.9%), except horizontal displacement (ICC = 0.54, CV = 20.6%). CONCLUSION: The 20-maximum test possesses excellent reliability for the assessment of trampoline performance in a wide population of national and international level gymnasts.
Keywords: Performance, elite athlete, gymnastics, time of flight, recovery
Abstract: BACKGROUND: Local vibration (LV) used as part of the warm-up can stimulate a specific body part and muscle group, potentially increasing muscle flexibility and performance. However, the effect of its combination with static stretching (SS) has not been thoroughly examined. OBJECTIVE: To elucidate the acute effectiveness of combining LV and SS (V+ S) on the ROM of ankle dorsiflexion, squat jump, counter-movement jump (CMJ) and the dynamic postural stability index (DPSI). METHODS: Fifteen healthy men who were regularly involved in recreational sports participated in this study. Static Stretching, V+…S, and non-stretching condition (control) were assigned randomly and the intervention period for each condition was five minutes. RESULTS: The dorsiflexion improved significantly in SS and V+ S compared to the control. The CMJ height decreased significantly following SS compared to V+ S and control. CONCLUSIONS: This study suggests that V+ S improves ankle dorsiflexion ROM without compromising jump performance. Local vibration device could be an effective element in warming up but further research is warranted.
Keywords: Static stretching with local vibration, vertical jump, dynamic postural stability
Abstract: BACKGROUND: The use of post-activation potentiation (PAP) exercises at the end of the warm-up may increase muscles nerve conduction speed and per consequent improve speed, strength and explosive power performances. OBJECTIVE: To assess the effect of PAP during warm-up using vertical or horizontal drop jumps on repeated sprints performance combined with countermovement jump in young handball players. METHODS: 12 young handball players participated in this study. Participants realized 3 randomized warm-up protocols: a warm-up without PAP, a warm-up with PAP using vertical drop jumps, and a warm-up with PAP using horizontal drop jumps. After the…assigned PAP protocol, the subject realized a counter movement jump as a reference value (CMJ r ), and thereafter repeated sprint tests with and without changing of direction (six maximal 2 × 12.5 m shuttle sprints and six maximal 25 m straight sprints, respectively) combined with vertical jumping. RESULTS: Horizontal drop jump during warm-up showed larger improvements in repeated sprints performance with and without change of direction for the parameters best time and mean time, compared with warm up without drop jumps (p < 0.01) and warm up with vertical drop jumps (p < 0.05). Vertical drop jump performance during warm-up induced greater gains in countermovement jump reference value in comparison with warm up without drop jump (p < 0.01), or warm up with horizontal drop jump (p < 0.01). CONCLUSION: PAP during warm-up using horizontal drop jump improves repeated sprints performance with and without changing of direction while PAP using vertical drop jump improves CMJ reference value.
Keywords: Countermovement jump, drop jump, post activation potentiation, repeated sprints
Abstract: BACKGROUND: Although the common practice of verbal encouragement is scientifically supported, its effect on the maintenance of force output in fatiguing exertions is unknown. OBJECTIVE: To examine the effects of verbal encouragement on exercise-induced quadriceps and knee joint function during three sets of knee extension exercise. METHODS: Sixty-five healthy males (23.3 years, 175.8 cm, 75.3 kg) underwent testing using the administration of verbal encouragement (n = 32) or not (n = 33) during assessment of quadriceps and knee joint function. Assessments were performed…at baseline and times 1, 2, and 3. The knee concentric isokinetic extension at 60 ∘ /s, was performed between the time points. For quadriceps function, maximal isometric strength and activation (central activation ratio) were recorded. Absolute error values on knee flexion replications at 15 ∘ or 45 ∘ were recorded for knee joint function. RESULTS: There was no verbal encouragement effect over three sets of exercise in quadriceps strength (condition × time: F 3 , 189 = 1.71, p = 0.17) and knee flexion replication (condition × time for 15 ∘ : F 3 , 189 = 0.11, p = 0.96; 45 ∘ : F 3 , 189 = 0.63, p = 0.6). However, subjects who had received verbal encouragement maintained quadriceps activation (condition × time: F 3 , 189 = 5.49, p = 0.001). Specifically, quadriceps activation in the verbal condition was 3.0% higher at time 2 (p = 0.01) and 4.7% higher at time 3 (p = 0.0003) versus in the non-verbal condition. CONCLUSIONS: Verbal encouragement appears to be effective in maintaining central activation, but is insufficient for promoting strength. This supports the idea that peripheral contributing factors play a larger role in force production when performing multiple sets of exercises.
Keywords: Maximal voluntary isokinetic contraction, central activation ratio, knee joint position sense, exercise-induced muscle fatigue
Abstract: BACKGROUND: Comparison of knee loads on a Smith machine, which is utilised for maintenance of health and rehabilitation, has not been attempted. OBJECTIVE: This study compared lower limb muscle and knee joint forces during front and back squats performed on a Smith Machine. METHODS: Eleven participants performed front and back squats with loads at 40%, 60% and 80% of their back squat 1-RMs. Ground reaction forces and three-dimensional full body motion were collected and used for modelling lower limb muscle and knee joint forces. RESULTS: Larger loads increased tibiofemoral compressive…force during back squat at 80% compared to 40% (p < 0.01; d = 1.58) and to 60% (p < 0.01; d = 1.37). Patellofemoral compressive (p = 0.96) and tibiofemoral shear forces (p = 0.55) were not influenced by external load or type of squat. Gluteus medius and minimus produced more force at 80% compared to 60% (p = 0.01; d = 1.10) and to 40% (p < 0.01; d = 1.87) without differences for other muscles (p = 0.09–0.91). CONCLUSIONS: Greater external load was associated with increase in gluteus medius and minimus force and with increased tibiofemoral compressive force without effects on tibiofemoral shear force, patellofemoral compressive force or other lower limb muscle forces.
Keywords: Joint loading, 1-RM, OpenSim, biomechanical modelling, resisted training
Abstract: BACKGROUND: The abdominal muscles play an important respiratory and stabilization role, and in coordination with other muscles regulate intra-abdominal pressure (IAP) to stabilize the spine. OBJECTIVE: To examine a new, non-invasive method to measure activation of the abdominal wall and compare changes in muscle activation during respiration while breathing under a load, and during instructed breathing. METHODS: Thirty-five healthy individuals completed this observational crossover study. Two capacitive force sensors registered the abdominal wall force during resting breathing stereotype, instructed breathing stereotype and under a load. RESULTS: Mean abdominal wall force…increased significantly on both sensors when holding the load compared to resting breathing (Upper Sensor: P < 0.0005, d = - 0.46, Lower Sensor: P < 0.0005, d = - 0.56). The pressure on both sensors also significantly increased during instructed breathing compared to resting breathing (US: P < 0.0005, d = - 0.76, LS: P < 0.0005, d = - 0.78). CONCLUSIONS: The use of capacitive force-sensors represent a new, non-invasive method to measure abdominal wall activity. Clinically, belts with capacitive force sensors can be used as a feedback tool to train abdominal wall activation.
Abstract: BACKGROUND: The hand-grip strength test has been widely adopted to evaluate upper limb strength. Other field based tests as push-ups and pull-ups are commonly used for the same purpose. It is however unclear if these may be used interchangeably for upper body strength evaluation. OBJECTIVE: The purpose of this investigation was to evaluate strength endurance of the upper body and understand which test could be the most appropriate for upper body evaluation. METHODS: Thirty-eight healthy young male participants were tested with three tests comprised of: 1) push-ups (PS), 2) pull-ups (PL) and 3)…parallel dips (PD) performed to exhaustion. Grip strength (GS), total number of repetitions, time-to-complete the test, repetition cadence and rate of perceived exertion (RPE) were also retrieved for investigation. RESULTS: Repetitions, time-to-complete the test and repetition cadence significantly differed across the three tests (p < 0.001). No difference in the RPE was present. No correlation was present between GS and the other tests. No correlation was present between RPE and performance values and time-to-complete the tests. BMI was positively correlated to RPE in all tests. All tests strongly correlate to each other (PS vs. PL r = 0.55; PS vs. PD r = 0.64; PL vs. PD r = 0.70) and to time-to-complete the test (PS r = 0.79; PL r = 0.69; PD r = 0.66). Only the results of the PD correlate to their respective repetition cadence (r = 0.66). CONCLUSIONS: GS is not suitable to evaluate strength endurance. PS, PL and PD are all suitable to evaluate strength endurance. However, PD may be preferred to evaluate the upper body, if velocity also needs to be taken into account.
Abstract: BACKGROUND: Skeletal muscle strength can be impacted by various factors. However, the possible effects of different forms of exercises on the elderly’s muscle strength remain unknown. Furthermore, whether the level of physical activity influences the effects of an exercise-based training also remains unclear. OBJECTIVE: To investigate the characteristics of fatigued quadriceps by continuous maximum knee extension movements among different male groups under different physical conditions. METHODS: A total of 36 male participants (24 elderly and 12 youth) were divided into three groups, namely, young male group, and two groups of elderly participants: physically…active and physically inactive. All groups underwent two sets of fatigue procedures. They initially finished 30 isokinetic maximum knee extension contractions at 60 ∘ /s. Three days later, they completed 50 isokinetic maximum knee extension at 180 ∘ /s. Then, their muscle strength characteristics were assessed. RESULTS: During the 60 ∘ /s fatigue test the total work of the dominant and non-dominant quadriceps in the two elderly groups was significantly lower than that of the young male group (p < 0.05). Moreover, the total work of dominant quadriceps in physically active elderly male group was significantly higher than physically inactive male group in the middle (71.1 ± 12.0 vs. 52.0 ± 18.5 J) and the last third (60.9 ± 8.6 vs. 44.4 ± 15.4 J, p < 0.05). During the 180 ∘ /s fatigue test the total work of dominant and non-dominant quadriceps in young male group was significantly higher than their elderly counterparts (p < 0.05). Moreover, the total work of dominant quadriceps in physically active elderly male group was significantly higher than in the physically inactive male group in the first (48.9 ± 4.6 vs. 31.7 ± 6.3 J), the middle (41.2 ± 4.8 vs. 26.1 ± 3.5 J), and the last third (33.3 ± 7.0 vs. 20.3 ± 3.1 J, p < 0.05). CONCLUSION: Exercise is associated with improved function and fatigue resistance of the quadriceps in elderly people. Moreover, the implications of the bilateral quadriceps’ imbalance in this group may be of functional importance and should thus be clinically considered.