Isokinetics and Exercise Science

BACKGROUND: Jamar dynamometer and modified sphygmomanometer(SphM) are used to evaluate grip strength (GS) in patients with rheumatoid arthritis (RA). However, their scores are not interchangeable.

OBJECTIVES: The aim of this study was to describe the intertrial reliability of grip strength measures obtained with Jamar dynamometer and an SphM, and delineate the relationship of the measures obtained with these two instruments when they were used in patients with RA.

METHODS: Patients were eligible volunteers among 74 consecutive patients with definite diagnosis of RA. The data from 61 patients were analyzed. Student's t test was used to compare GS means of the male and female patients. Intertrial reliability was examined using one-way repeated measures ANOVA and intraclass correlation coefficients. The relationship between the measures was established using Pearson correlation coefficients and inverse regression analysis. The latter allowed the generation of conversion tables.

RESULTS: GS means were not significantly different between the genders. Both instruments demonstrated excellent intertrial reliabilities. No significant difference was observed among the trials with each instrument. There was a strong relationship between the instruments' scores. This relationship was proven to be linear. Conversion equations were calculated based on the instruments' scores.

CONCLUSION: Clinicians now have a table to convert hand strength scores between Jamar dynamometer and an SphM, and can determine the deviation from the normal in patients with RA.

This study aimed to analyze the influence of holographic bracelets on body balance and peak torque in soccer athletes through a quintuple-blind, placebo-controlled, crossover randomized trial. Twenty-eight male athletes were evaluated in a stabilometric baropodometer(DIASU®) and performed a protocol involving concentric contractions of the knee at 60°/s. Athletes were evaluated in three situations: no bracelet (baseline), with a placebo bracelet (PB) and holographic bracelet (HB). Comparing the mean torque peak at 60°/s during knee extension, there was no statistical difference for the dominant limb (p=0.713) and non-dominant (p=0.996) between the baseline, PB and HB groups. No statistical difference was found comparing the mean oscillation ellipses from the right foot with eyes open (p=0.359) and with eyes closed (p=0.173), as well as from the left foot with eyes open (p=0.891) and with eyes closed (p=0.778). In conclusion, holographic bracelet has no influence on either body balance or knee muscle performance in athletes.

BACKGROUND: Circadian rhythms, and their potential influence on athletic performance, have been the subject of a number of investigations.

OBJECTIVE: This study aimed to determine the influence of circadian rhythms on the peak isokinetic force of the quadriceps and hamstring muscle groups, and the relationship of cortisol level with these measures.

METHODS: Twelve male and twelve female participants completed maximal isokinetic flexion and extension movements of their dominant leg at 60°/s using an isokinetic dynamometer. Data were collected at 09.00(Session A), 14.00 (Session B) and 18.00 (Session C). Salivary cortisol was also obtained immediately prior to each session. Differences in isokinetic strength parameters and salivary cortisol concentrations, between the three sessions, were examined using 2 × 3 mixed ANOVAs. Pearson correlations were used to examine the relationship between isokinetic strength and salivary cortisol.

RESULTS: For all of the flexion parameters, but none of their extension counterparts, session C was associated with significantly greater isokinetic strength compared to session A. No significant relationships were observed between measures of isokinetic strength and cortisol.

CONCLUSIONS: The findings from this investigation suggest that both male and female athletes performing knee flexion strengthening exercises should conduct their training/competitions in the late afternoon or early evening in order to maximize performance.

BACKGROUND: There are alterations in strength in relation to menstrual cycle phase but little data attributing these responses to female sex hormone levels using a pseudo-menstrual cycle group as control.

OBJECTIVE: Examining the effects of menstrual cycle phase on the development of peak torque across a range of isokinetic speeds.

METHOD: 17 well trained females, 11 formed the non-oral contraceptive group (n-OC) (age 20.7± 1.4 yrs, mass 59.2 ± 6.9 kg, height 166.8 ± 7.1 cm) and 6 the oral contraceptive control group (OC) (age 20.3 ± 0.5 yrs, mass 60.5 ± 4.2 kg, height 164.8 ± 4.8 cm). Concentric strength of the knee flexors and extensors (60–240°/s) was assessed, corresponding to menstruation(MEN), mid-follicular (mFOL), mid-luteal (mLUT) and pre-menstrual (pMEN).

RESULTS: For n-OC significant decreases in peak torque production of the extensors at 120°/s (P=0.0207) (MEN) and of the flexors at 60°/s (P=0.0116) (MEN) and 120°/s (P=0.0282) (MEN) were observed compared to pMEN. No significant differences were observed across any menstrual cycle phase and peak torque for the OC group (p> 0.05). Significant positive correlations were observed (mLUT) between peak torque and oestrogen at 60°/s (P=0.040) and 120°/s (P=0.031).

CONCLUSIONS: There are significant fluctuations in peak torque of the knee extensors in response to phases of the menstrual cycle associated with variances in the female sex hormones. The findings have implications for the planning of strength training in female athletes.

BACKGROUND: Objective measurement of trunk muscles strength in ankylosing spondylitis (AS) may provide clinical information that can be used to evaluate functional disability.

OBJECTIVE: To compare the isokinetic strength of trunk muscles in AS patients with healthy subjects.

METHODS: Thirty-four patients with AS and thirty-one healthy subjects were enrolled. Patients with spinal ankylosis and bridged syndesmophytes in the lumbar and dorsal vertebrae were excluded. Trunk flexor and extensor strength was measured at: 60 and 90°/sec.

RESULTS: When compared with the control group, AS patients demonstrated 38% and 24% decrease in the extensor and flexor strength, respectively (p< 0.05). In addition, the flexor/extensor strength ratio was 1.0 and 0.8 in the patients and control subjects, respectively.

CONCLUSIONS: In view of the relatively selective extensor weakness we recommend assessment of trunk muscle strength in these patients for guiding clinicians regarding possible reconditioning exercises in the early period of AS.

BACKGROUND: Team sport athletes require dynamic stability in unilateral activities for their sports, which necessitates some degree of knee flexion and extension strength.

OBJECTIVE: To analyze the possible association of knee extension and flexion strength with dynamic stability, as measured by the Star Excursion Balance Test (SEBT).

METHODS: Sixteen male team sport athletes completed the SEBT, which involves a series of unilateral squats with the subject maximally reaching with the other leg in eight directions. Knee muscle strength was measured isokinetically both concentrically (60°/s, 180°/s, 240°/s) and eccentrically(30°/s). Subjects were divided into better and lesser groups based on mean functional reach distance. A 1-way analysis of variance (p⩽ 0.05) determined between-group differences in reach distances and relative torque.

RESULTS: Subjects with better dynamic stability generated greater knee extensor torque concentrically at 180°/s for the right leg, and at all speeds for the left leg. The effects of knee strength were particularly noteworthy for the left leg, as subjects with better dynamic stability reached significantly further across all 8 directions.

CONCLUSION: The results indicate that greater knee extensor strength may enhance unilateral dynamic stability in team sport athletes.

BACKGROUND: There are few standardised assessments of unilateral muscular endurance and little data examining the validity and reproducibility of isokinetic unilateral muscular endurance performance measures.

OBJECTIVE: To examine the validity and reproducibility of an isokinetic assessment of lower limb unilateral muscular endurance performance.

METHODS: Thirty individuals (15 endurance trained and 15 non-endurance trained) repeated a time to exhaustion (TTE) based endurance protocol on separate days. Procedures were conducted on an isokinetic dynamometer and involved leg extension through 135° of the dominant leg. The TTE protocol required participants to perform unilateral isokinetic leg extensions at 60% of individual maximal voluntary contraction (MVC) until the specified intensity and frequency could not be maintained.

RESULTS: The endurance trained individuals reached significantly greater TTE than their non-endurance trained counterparts (P< 0.001). Systemic bias was small (< 5%) and measures were similar between trials. Test-retest reproducibility statistics were as follows; CV: 6.9%; LOA −170.1 to 139.5; RLOA: −0.320 ×/÷ 0.257. Relative reproducibility statistics were tight between trials (significant correlation P< 0.001).

CONCLUSIONS: Data demonstrate the validity and tight test-retest reproducibility of the aforementioned assessment of unilateral muscular endurance performance.

BACKGROUND: Aim of this study is to evaluate ankle joint position sense (JPS) in the diabetic patients without peripheral neuropathy (PN). The hypothesis was that diabetes would lead to decreased JPS even if there was no PN.

METHODS: Thirty-seven patients with diabetes and 22 healthy controls were included in the study. PN was detected with the use of Semmes-Weinstein Monofilament test (SWMT), vibration testing by the timed method (128 Hz diapason) and two point discrimination sensation test. JPS was measured as the subjects' ability to actively reproduce target ankle dorsiflexion (DF) and plantarflexion (PF). The concentric isokinetic peak torques of the ankle DF and PF were recorded using the Biodex® System 3 Dynamometer.

RESULTS: JPS was significantly lower in diabetic patients than control subjects. PF isokinetic muscle torque at 30°/s, 60°/s and 180°/s was significantly lower in diabetic patients than control subjects but DF muscle torque did not differ between the groups.

CONCLUSIONS: Diabetic patients displayed decreased ankle joint position sense and muscle torque even though they had no peripheral neuropathy. Treatment strategies aiming at improving proprioception and muscle strength in early stage could be beneficial to prevent the patients from diabetes complications.

The purpose of this paper is to describe a portable belt-stabilized hand-held dynamometry (HHD) set-up for measuring knee extension force and to compare the magnitude and reliability of forces obtained with the set-up to those obtained without belt-stabilization. Measures for single-limb knee extension force were obtained via HHD from 16 young participants by 2 testers of substantially different strength. Measurements were obtained during 2 sessions 1 week apart. Testing was performed with participants in a bariatric chair – with and without HHD belt-stabilization. Data from the first session were used to compare the magnitude of knee extension forces. Data from both sessions were used to examine reliability via intraclass correlation coefficients (ICCs) and Bland-Altman plots. Forces measured with belt-stabilization were significantly (p< 0.001) higher than those measured without belt-stabilization. The differences were greater for male participants (p=0.006) and the female tester(p=0.001). Intertester reliability was poor for measurements obtained without belt-stabilization (ICC=0.17) but good for measurements obtained with belt-stabilization (ICC=0.84). Differences between testers increased with the magnitude of force measured when no belt-stabilization was provided but not when belt-stabilization was used. Test-retest reliability was good when belt-stabilization was employed (ICC=0.87 and 0.92). When belt-stabilization was not used, the test-retest reliability was acceptable for the male tester (ICC=0.77) but not the female tester (ICC=0.50). In conclusion, the set-up examined is affordable, portable and easy to assemble. It allows for rapid testing of knee extension strength. With HHD belt-stabilization, the set-up can be recommended for clinicians and researchers requiring objective measures of knee extension strength in diverse settings.

Author Index Volume 21 (2013)

Keyword Index Volume 21 (2013)