Isokinetics and Exercise Science - Volume 30, issue 4
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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: The knee is one of the most common sites of injuries among soccer players. The incidence of knee injuries can be reduced by improving the neuromuscular control and core stability. OBJECTIVE: This study aimed to evaluate the effectiveness of injury prevention programs that include core stability exercises in reducing the incidence of knee injuries among soccer players. METHODS: Data were obtained from different databases (1985–2021). Only randomized controlled trials that used injury prevention programs that include core stability exercise to prevent knee injuries were included. The keywords used during the search were…‘knee injuries’, ‘core stability exercises’, ‘FIFA 11+ ’, ‘prevention of knee injuries’, ‘anterior cruciate ligament injury’ and variations of these search terms. RESULTS: The pooled results of 7828 soccer players and 863700 exposure h showed an overall injury reduction of 56% per 1000 h of exposure in the intervention group compared to the control group with an injury risk ratio of 0.44 (95% CI 0.321–0.619; P = 0.001). CONCLUSIONS: Injury prevention programs that include core stability exercises reduce knee injury rates among soccer players by 56% (46% in male and 65% in female soccer players).
Abstract: BACKGROUND: Ultrasound is an important tool to diagnose many clinical conditions. Yet hand-held devices may be prone to more data variability in part from the greater likelihood of human error. OBJECTIVE: Quantify intra-rater reliability of subcutaneous skin fold thickness from a hand-held ultrasound device. PARTICIPANTS: College-age subjects (18 men, 14 women) submitted to two sets of ultrasound subcutaneous skin fold measurements spaced (mean + sem) 10.6 + 2.2 days apart. Per measurement, they stood relaxed as ultrasound measured the subcutaneous skin fold thickness that covered their left…leg’s calf muscle group. Measurements occurred with a hand-held device (BodyMetrix Pro System BX2000; Livermore, CA) used in accordance with the manufacturer’s guidelines. Four subcutaneous measurements were made 90 ∘ apart (anterior, medial, posterior, lateral) at the portion of the left calf with the largest circumference. To assess intra-rater reliability, we used intraclass correlation coefficients, limits of agreement, coefficient of variation and the smallest real difference. RESULTS: Intra-rater reliability was high for most of our statistical tests. CONCLUSION: Despite the relatively long period between measurements, our hand-held ultrasound device exhibited a high degree of intra-rater reliability. Given our results, ultrasound measurements may be a useful tool to quantify skin fold thickness.
Keywords: Intraclass correlation coefficients, variability, BodyMetrix Pro System BX2000
Abstract: OBJECTIVE: Having participants perform 50 maximal isokinetic contractions, as introduced by Thorstensson and Karlsson (1976), is to this day one of the most commonly used fatigue protocols. Purpose: To determine to what extent a Thorstensson fatiguing protocol affects isokinetic and isometric performance characteristics. METHODS: Twenty-five college-aged men performed an isokinetic fatigue protocol consisting of 50 maximal elbow flexions at a moderate speed (180 ∘ ⋅ s - 1 ). Pre- and post-tests were used to calculate fatigue indices (FI%) for the following variables: isometric and isokinetic peak…torque (PT), isometric rate of torque development (RTD), and maximum acceleration (ACC max ). RESULTS: Each of the four dependent variables significantly decreased with fatigue (each demonstrated p < 0.001), but not of the same magnitude. Isometric PT FI (- 18.7%) was significantly less than isokinetic PT FI (- 45.1%, p ⩽ 0.001) and ACC max FI (- 26.3%) was significantly less than isometric RTD FI (- 54.9%, p ⩽ 0.001). There was a significant positive relationship between isometric and isokinetic PT FI% (r = 0.60, p < 0.002) as well as between isometric PT FI% and RTD FI% (r = 0.40, p < 0.046). There was no significant relationship observed between RTD FI% and ACC max FI% nor between isokinetic PT FI% and ACC max FI%. CONCLUSIONS: This investigation observed different patterns of response in maximal strength between isometric and isokinetic assessments following a isokinetic fatigue protocol. Additionally, the ability to rapidly generate strength and velocity had significantly different responses to fatigue between isometric and dynamic assessments. Due to these different responses, we recommend that assessments of fatigue at least include the same testing modality as the modality of the fatigue protocol.
Abstract: BACKGROUND: Studies of coactivation have typically utilized single movement isometric or isokinetic fatiguing muscle actions. OBJECTIVE: The purpose of the current study was to examine coactivation of the biceps brachii (BB) and triceps brachii (TB) in response to a maximal, reciprocal, isokinetic fatiguing task of the forearm flexors and extensors at slow (60 ∘ /s) and moderate (180 ∘ /s) isokinetic velocities in men. METHODS: Ten men (mean ± SD: age = 21.6 ± 1.3 years) completed 50…consecutive, maximal, reciprocal, isokinetic muscle actions of the right forearm flexors and extensors at 60 and 180 ∘ /s. The amplitude (AMP) and mean power frequency (MPF) contents of the electromyographic (EMG) and mechanomyographic (MMG) signals from the BB and TB were recorded simultaneously throughout the fatiguing task. Repeated measures ANOVAs with Tukey post hocs were used to determine mean differences for the torque and neuromuscular parameters across repetitions. RESULTS: The torque analyses indicated greater fatigability at 180 ∘ /s, compared to 60 ∘ /s (p = 0.02). There were no significant changes in EMG AMP for either muscle during flexion or extension at 60 ∘ /s (p > 0.05). At 180 ∘ /s, there were significant increases in agonist EMG AMP (p = 0.01 to 0.004), however, no changes in antagonist EMG AMP (p > 0.05). For EMG MPF, there were significant decreases during flexion and extension (p < 0.001 to p = 0.02) at both velocities, collapsed across muscle. There were no significant (p > 0.05) changes across repetition for MMG AMP or MPF. CONCLUSIONS: This study indicated velocity-specific responses to fatigue, with a greater magnitude of fatigability at 180 ∘ /s. Furthermore, despite increases in EMG AMP of the agonist muscles at 180 ∘ /s only, it was not sufficient to alter the ratio of coactivation, likely due to common neural drive between muscles. Thus, the decreases in torque in the present study were not attributable to increases in coactivation.
Abstract: BACKGROUND: There are conflicting reports on the acute effects of stretching on muscle strength. Some studies report reduction in muscle strength however others report no change following stretching. OBJECTIVE: To assess the acute effects of static stretching (SS) of different durations on the isometric maximum voluntary contraction force (MVCF) of the calf muscle. METHODS: Pretest-posttest experimental design was used. Ten male participants (mean age 25.4 ± 2.11 years) participated in three experimental trials: SS for 2-minutes (SS 2 ), 4-minutes (SS 4 ), and…8-minutes (SS 8 ). MVCF was measured before, immediately after, at 10- and 20-minutes post-stretch intervals. Each SS trial involved varied repetitions of 30-seconds stretches and 20-seconds relaxation periods. The isometric maximum voluntary contraction force (MVCF) was the outcome measure. RESULTS: SS 2 , SS 4 , and SS 8 did not change the MVCF at 0-, 10- and 20-minutes post stretching intervals (p > 0.05). CONCLUSIONS: 2-, 4-, and 8-minutes intermittent SS did not change the isometric muscle strength in the calf muscle up to 20-minutes after stretching and thus can safely be performed before those sporting events that require significant muscle strength.
Abstract: BACKGROUND: The relationship between strength and throwing velocity is much investigated in handball, but core strength is largely ignored. Only four studies have investigated the effect of core training on handball throwing velocity, reporting conflicting results in amateur players. However, lack of specificity and deficient technical execution of throwing in amateurs can obscure the results. OBJECTIVE: To examine the direct association between trunk flexion strength and throwing velocity in elite handball players, using women as a model. METHODS: Sixteen women players from an elite-level Norwegian handball team participated in the study. Strength in…trunk flexion, shoulder extension, internal shoulder rotation, and forearm pronation was assessed using isokinetic dynamometer measurements (peak moment, total work, angular impulse). Throwing velocity in both the standing throw with run-up and the jump throw was determined from motion capture measurements. To account for arm strength, the association between trunk flexion strength and throwing velocity was examined using partial correlation analyses. RESULTS: No significant association was found between any measure of trunk flexion strength and throwing velocity for either throwing technique (explained variance ⩽ 13.7%). CONCLUSIONS: The results indicate that isolated, dynamic trunk flexion strength is not a differentiating factor for handball throwing velocity in elite women players.
Keywords: Core, isokinetic, performance, throw, training
Abstract: BACKGROUND: External focus isometric exercises using a paper balloon can change trunk muscle activation in the chest squeeze; however, it is unknown whether this method affects muscle activities in conventional exercises. OBJECTIVE: To check variations of trunk muscle activity during front plank (static task) and shoulder press (dynamic task) both with and without instruction to avoid crushing an object. METHODS: Twenty-six healthy adult males aged 19–49 were recruited. Ten trunk muscle activities were measured using surface electromyography during a front plank and dynamic shoulder press exercises, both with and without external-focus instruction.…RESULTS: Adding the external-focus using the paper balloon to the front plank significantly activated 8 out of the 10 muscles. In the downward shoulder press, 5 out of 10 muscles with 50% 1 RM, 2 out of 10 muscles with 100% 1 RM were significantly activated. CONCLUSIONS: Adding external-focus instruction using paper balloon increases trunk muscles in front plank and shoulder press while possibly improving trunk stability. Novel exercises using paper balloon may efficiently activate specific muscles without external loading thus possibly reducing the stress on the involved joints during exercise.
Abstract: BACKGROUND: While linear transducers are the most accurate velocity monitoring devices, the horizontal motion of the barbell seems to affect its measurement error. OBJECTIVE: To explore the effect of cable inclination of the GymAware and T-Force linear transducers on the intra-session reliability and magnitude of kinematic variables during the Smith machine bench press exercise. METHODS: Twenty-eight resistance-trained males performed 2 blocks of 12 repetitions (4 repetitions at 40-60-80%1RM). In half of the repetitions with each load the two measuring systems were either vertically aligned with the barbell or positioned 15-cm away from the…vertical projection of the barbell. RESULTS: Displacement and mean velocity variables were recorded with a high and comparable intra-session reliability regardless of the cable position and measuring system (CV= 𝑟𝑎𝑛𝑔𝑒 1.79–8.38%; ICC= 𝑟𝑎𝑛𝑔𝑒 0.69–0.98). The inclined cable position provided a lower displacement and mean velocity than the vertical cable position and the differences were comparable using both the GymAware (⩽ 1.52 cm; ⩽ 0.05 m⋅ s - 1 ) and T-Force (⩽ 1.53 cm; ⩽ 0.04 m⋅ s - 1 ). CONCLUSIONS: These results indicate that repeatable findings of kinematic variables can be obtained regardless of the cable position, but for comparative purposes, the cable position should remain constant from the start to the end of the lifts.
Keywords: Monitoring, resistance training, sport technology, testing, velocity-based training
Abstract: BACKGROUND: For years, the effects of music on exercise performance have been researched. Recovery is extremely important for athletes, and therefore any factor that could affect it is of importance. OBJECTIVE: To assess the influence of listening to music on recovery after an anaerobic-exercise. METHOD: 25 male athletes (age 21.76 ± 1.84 years) visited the laboratory on two occasions over a week. They performed the Wingate Anaerobic Test (WAnT) on two identical conditions but recovery was conducted ‘with’ and ‘without’ listening to music. Blood lactate concentration values were determined at 1,…5, 10 and 15 minutes during the recovery from the exercise. Heart rate (HR) values were determined every minute of the 15 minutes of recovery. RESULTS: There was no difference in the mean blood lactate concentration and HR during the recovery with and without music (p > 0.05). Results showed no significant differences between 2 recovery conditions in heart rate or blood lactate. CONCLUSIONS: Music cannot improve recovery after anaerobic performance and it cannot be used as a mean to enhance recovery after an anaerobic-performance.
Abstract: BACKGROUND: Postural control deficits are prevalent in children with hemiplegic cerebral palsy (CwHCP). Therefore, the best rehabilitative strategies for remediating these deficits are warranted, which could then enhance function. OBJECTIVE: To examine effects of a block versus an alternating sequence of balance training (BT) and plyometric training (PT) on postural control in CwHCP. METHODS: Forty-eight CwHCP (812 years) were randomized to a block or an alternating BT/PT training. The block BT/PT group (n = 24) received a six-week BT followed by a six-week PT, twice/week over 12 consecutive weeks.…The alternating BT/PT group (n = 24) received an interchanging sequence of BT and PT changed every two weeks for 12 weeks. Postural control [center-of-pressure reaction time (RT), movement velocity (MV), maximum excursion (ME), end-point excursion (EE), and directional control (DC)], functional balance (indicated by pediatric balance scale; PBS), and balance/risk-of-falls during walking (denoted by dynamic gait index; DGI) were assessed before and after training. RESULTS: The block BT/PT group showed greater enhancements in postural control variables [RT (P = 0.004), MV (P = 0.028), ME (P = 0.002), EE (P = 0.003), and DC (P = 0.012)] and functional balance (P = 0.006), and lesser risk-of-falls during walking (P = 0.018) when compared to the alternating BT/PT group. CONCLUSION: The block BT/PT sequence is more effective to enhance postural control than the alternating sequence in CwHCP.