Isokinetics and Exercise Science - Volume 24, 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: LED phototherapy can attenuate muscle fatigue and accelerate muscle recovery in young persons, but little is known about photobiomodulation effects on muscle strength in the elderly. OBJECTIVE: To assess the effects of LED phototherapy on the grip strength and muscle fatigue of wrist flexors in elderly women. METHODS: Twenty-nine women were recruited and allocated to Placebo Group (PG) (n= 14) and LED Group (LG) (n= 15). Grip strength, number of resisted wrist flexion repetitions, and serum creatine kinase (CK) were measured. The subjects were irradiated with one diode (638 nm, 150 mW,…11.7 J/cm2 , 4.5 J/point) at four points on the wrist flexor muscles, and fatigue was induced by exercise using 75% of one maximum repetition (1MR). When muscle fatigue was reached, grip strength and CK were reassessed. RESULTS: In the LG, there was no intra-group difference for grip strength (N), 217.7 ± 34.3 to 209.9 ± 35.3 (p = 0.063) whereas in the PG, there was decrease in strength from 203.0 ± 22.5 to 181.4 ± 21.6 (p < 0.001). LED increased the number of repetitions by 22.0%. An increase in CK (U/L) was observed in PG in all post-fatigue periods (p = 0.003) but no difference was found in the LG (p = 0.972). CONCLUSIONS: A single application of LED before muscle fatigue induction may effectively maintain grip strength and reduce muscle fatigue and damage.
Abstract: BACKGROUND: The gluteus medius (GM) which functions mainly in weight-bearing to stabilize the pelvis in a unilateral stance against gravity has been described as having several anatomic subdivisions. OBJECTIVE: The aim of this study was to compare the activation of the three GM subdivisions (anterior, medial, and posterior) during four weight bearing exercises. METHODS: This study investigated GM activation in 15 healthy adult males during four weight-bearing exercises; hip fire hydrant, standing forward bent-horizontal hip abduction (SFB-HHA), wall press and pelvic drop. Muscle activations in the three GM subdivisions were measured using electromyography…(EMG) and compared using a repeated one-way ANOVA. RESULTS: All GM subdivisions showed higher activation during high position exercises (pelvic drop, SFB-HHA, wall press exercise) than during the low position exercise (hip fire hydrant). The anterior subdivision showed higher activity during pelvic drop exercise than during SFB-HHA and wall press exercises. Higher posterior subdivision activity was observed during SFB-HHA compared to wall press and pelvic drop exercises, posterior subdivision activity was higher during wall press compared to pelvic drop. CONCLUSIONS: The results suggest that pelvic drop is the appropriate exercise to activate the anterior subdivision of the GM, whereas SFB-HHA is the best exercise to activate the posterior subdivision.
Abstract: BACKGROUND: Since a growing body of evidence points to mean training intensity over a season as a key factor to performance improvements, and there is wide evidence of the benefits of high-intensity intermittent training (HIIT) for endurance athletes, coaches need further information about the acute impact of typical HIIT workouts on endurance runners. OBJECTIVE: To compare the physiological strain and muscular performance parameters of endurance runners during two HIIT workouts by determining whether a typical HIIT for endurance runners (10 × 400 m) leads to a similar impact as a HIIT protocol (40 ×…100 m) that increases the average training pace despite maintaining the same training volume. METHODS: Eighteen endurance runners performed 2 HIITs. Metabolic (blood lactate [BLa], blood ammonia [BAmm]), neuromuscular (countermovement jump [CMJ], handgrip strength test [HS]), and physiological responses were monitored during both protocols. RESULTS: No significant differences between HIITs were found for BLa_1 min post-test, BAmm, HS and HRpeak. Significant differences were found in fatigue-induced changes in CMJ performance (-0.36 cm in 40 × 100 m; +1.48 cm in 10 × 400 m), and in average pace (P< 0.001) which was faster during the 40 × 100 m. CONCLUSIONS: Despite similar physiological, metabolic, and HS responses, the 40 × 100 m protocol allowed runners to train at a higher intensity, which might have important effects on the training prescription for endurance runners.
Abstract: BACKGROUND: Yoga's benefits on various aspects of health for sighted children is substantially supported by the literature. This study aimed to extend those fidings to children with visual impairment. OBJECTIVE: The aim of the study was to measure changes in upper extremity strength and motor speed in children with visual impairment following 16-weeks of yoga training. METHODS: This was a two arm pre post, single blind, waitlist-controlled study. Eighty-three (yoga [n= 41], control [n= 42]) participants (aged 9-16 years) enrolled, 6 dropped out from the trial. Demographic characteristics were not significantly different between…the two groups. The following variables: upper extremity muscle strength; elbow flexion and elbow extension, pinch strength and motor speed were evaluated bilaterally using a handheld dynamometer, pinch dynamometer and finger tapping board respectively at baseline and after the 16-week intervention. SPSS-20 was used for statistical analysis. RESULTS: Significant improvements in all variables (P < 0.05) were observed in the yoga group for both limbs but no significant changes were observed in the control group. CONCLUSION: The study suggests that yoga may be considered an effective option to improve muscle strength and motor function in children with visual impairment.
Keywords: Muscles strength, motor speed, visual impairment, children, yoga
Abstract: BACKGROUND: The load that maximizes power output, commonly called ``optimal load'', has received wide attention for training and testing purposes. OBJECTIVE: To evaluate the reproducibility in the determination of the load that maximizes mean power (MP), mean propulsive power (MPP), and peak power (PP) during the bench press (BP) and bench press throw (BPT) exercises. METHODS: Twenty-two men conducted 4 evaluations after a preliminary BP 1-repetition maximum (1RM) determination. In a counterbalanced order, subjects performed 2 sessions of BP in one week and 2 sessions of BPT in another week. MP, MPP, and…PP at each tenth percentile (20-70% of 1RM) were recorded on each testing day. Two procedures were used to determine the individual optimal load: (1) Absolute: individual load with the highest power output; (2) Predicted: obtained from the parabolic load-power relationship. RESULTS: While acceptable reproducibility was found for MP in both exercises and procedures (ICC: 0.85-0.96; CV: 2.7%-12.2%), low reproducibility was obtained for MPP (ICC: -0.20-0.60; CV: 21.1%-29.3%), and PP (ICC: 0.42-0.78; CV: 17.8%-20.9%). CONCLUSIONS: The low reproducibility associated with the determination of the optimal load suggests that it may be unnecessary to look for a single optimal load for training.
Keywords: Bench press, bench press throw, mean power, mean propulsive power, peak power
Abstract: BACKGROUND: Vertical jumps are an important component to many athletic endeavors. Identification of performance variables that act as correlates to vertical jump prowess is important to help achieve success in sports. OBJECTIVE: To examine which performance-based variables (kinetic, temporal, force-time integrative, expressed relative to body mass) are the best correlates to vertical jump height and power. METHODS: Men (n = 117) performed vertical jumps on an instrumented platform placed aside a Vertec; both devices obtained data as jumps occurred. Vertec values were used to identify jump height and power, each of which served…as criterion measures. The platform provided six performance-based variables from the countermovement and takeoff phases of jumps; they were used to predict the variance per criterion measure via multivariate regression. RESULTS: With either jump height or power as a criterion, each analysis revealed a significant amount of variance correlated to our performance-based independent variables. Univariate correlations showed peak force and area under the curve were the best predictors of jump height and power variance. Our results concur with studies that employed similar subjects. CONCLUSIONS: Kinetic and force-time integrative variables are the best correlates to jump height and power values for criterion measures derived from an instrumented platform.
Keywords: Kinetic, temporal, force-time integrative, body mass
Abstract: BACKGROUND: Although several studies have focused on maximal O2 uptake (V ˙ O2max ) measured by a verification phase following the determination of peak O2 uptake (V ˙ O2peak ) by a graded exercise test, an explanation for the underlying mechanisms of the difference between V ˙ O2peak and confirmed V ˙ O2max is scant. OBJECTIVE: To explore the hypothesis that when the difference between V ˙ O2peak and…V ˙ O2max (ΔV ˙ O2 ) increases, the gap between peak stroke volume (SVpeak ) and SV level corresponding to V ˙ O2peak velocities (Δ SV) grows. METHODS: Nine moderately to well-trained male athletes (V ˙ O2max : 60.2 ± 7 mL ⋅ min-1 ⋅ kg-1 ) volunteered to take part in the study. Following familiarization session, volunteers were asked to perform submaximal and maximal graded exercise tests. Then, constant-loading SVpeak tests (using wattages in a range from 40-100% of V ˙ O2peak ) and verification phase (using wattages corresponding with 100-110% of V ˙ O2peak ) were conducted in a climatic chamber. RESULTS: The ΔV ˙ O2 was well correlated with Δ SV (Pearson r= 0.89; p≤ 0.001). The mean SVpeak of participants corresponded to 60.3 ± 18% of V ˙ O2peak . V ˙ O2max was significantly greater (11.2%) than V ˙ O2peak (60.2 ± 7 vs. 54.2 ± 8.1 mL ⋅ min-1 ⋅ kg-1 ) (p ≤ 0.01). CONCLUSIONS: V ˙ O2peak and V ˙ O2max differences may be related to the gap between SVpeak and SV at V ˙ O2peak .
Abstract: BACKGROUND: Active and passive interval during resistance exercises can cause different hemodynamic responses. OBJECTIVE: To evaluate the effect of passive and active intervals between sets of high-intensity resistance exercise on post-exercise hypotension in hypertensive women. METHODS: Fifteen sedentary women who have hypertension controlled by medication [64.1 ± 7.9 years, systolic blood pressure (SBP) < 140 mmHg, diastolic blood pressure (DBP) < 90 mmHg] performed one control session without exercise and two resistance exercises sessions with passive and active intervals between sets, in a randomized order. All hypertensive women participated in a supervised…resistance training session. SBP and DBP were measured in six different times for all sessions. The first two measures were at rest (10 and 15 minutes) followed by 15-minute intervals after the end of control/exercise sessions up to one hour. RESULTS: Post-exercise hypotension (p < 0.05) was observed in SBP after active intervals session compared with passive interval session, at 30 and 45 minutes. The area under the delta curve of SBP in the active protocol was ∼ 21 mmHg of hypotension during 60 minutes, 10 mmHg in passive protocol and 5 mmHg in the control session. CONCLUSIONS: Active intervals during high-intensity resistance exercises promote higher post-exercise hypotension compared with passive intervals.
Abstract: BACKGROUND: Kinesiotaping (KT) has become popular among athletic trainers and physical therapists. Most of KT studies investigated only the immediate responses, and only a few evaluated the long-term effects. OBJECTIVES: To evaluate the effects of 48 hours of KT on knee extensor performance of healthy subjects during isokinetic exercise at different muscle action velocities. METHODS: Twenty six healthy men were enrolled and the study presented a drop-out rate of 19%. Participants were randomly allocated to one of two intervention groups: 1. KT with the tape applied for activation of rectus femoris with 40%…tension 2. Control (CO) with the tape applied on rectus femoris without tension. Measurements were collected at baseline (BL) without KT, immediately (T0) post KT application, and 24 h (T24) and 48 h (T48) after KT application. The main outcome measures were Knee extension peak torque (PT), load range (LR) and time to reach the PT (TPT). RESULTS: There were no significant differences between KT and CO for PT, LR or TPT at 60 or 240°/s, and no significant differences on time (BL, IMD, 24 h and 48 h) for both groups. CONCLUSION: Kinesiotaping did not enhance knee extensor neuromuscular performance of healthy men at different muscle action velocities. An important finding was that the continued use of the Kinesiotaping (48 h) did not influence muscle performance.
Abstract: BACKGROUND: Hemiparesis causes a reduction in neuromuscular structure and function and affects the contractile properties of the plantar flexors. OBJECTIVE: To compare the triceps surae volume, activation and mechanical properties in hemiparetic stroke survivors to those of healthy subjects. METHODS: Twelve hemiparetic stroke survivors (mean age, 62 years) and twelve healthy subjects (mean age, 60 years) participated in the study. The triceps surae muscle volume was estimated by ultrasound and anthropometric data. Plantar flexor muscle activation and dorsiflexor co-activation were measured with surface electromyography, and isometric plantar flexor moment was measured with an…isokinetic dynamometer. Muscle quality was determined by the moment/muscle volume ratio. One-way ANOVA was used for between-groups comparisons (α = 0.05). RESULTS: The paretic and non-paretic limbs of stroke survivors showed smaller muscle volume (∼ 36% and ∼ 35%, respectively) than the dominant limb of healthy subjects (p< 0.01). The muscle quality was similar between the non-paretic limb and the dominant limb of healthy subjects (p> 0.05) but was lower in the paretic limb (p< 0.05). Peak moment was lower (∼ 61%) in the paretic and non-paretic (∼ 33%) limbs compared to the dominant limb of healthy subjects (p< 0.01). The paretic limb showed lower gastrocnemius medialis activation than did the non-paretic (∼ 45%) and dominant (∼ 33%) limbs of healthy subjects (p< 0.01). CONCLUSION: Structural and functional losses are higher in the paretic than in the non-paretic limb and in the non-paretic compared to a healthy limb.