Isokinetics and Exercise Science

Ankle or knee joint cooling has shown to increase muscle activation in controlled laboratory measurements.

To examine if a bilateral 20-min lower-extremity joint cooling alters maximal vertical jump heights over time.

Twenty-one healthy male basketball and volleyball players participated in this cross over study. One of three conditions was assigned for each session (ankle or knee joint cooling, or control). Subjects performed three maximal vertical jumps with (countermovement jump: CMJ) and without (squat jump: SJ) using muscle pre-stretching and arm swinging at baseline and after condition (0-, 10-, 20-, and 30-min post). To test joint cooling effects over time, we performed 3 × 5 mixed model ANOVAs and Tukey-Kramer tests.

Both joint cooling altered CMJ heights (F_8,280 = 2.29; p= 0.02). Compared to the baseline measurements, subjects jumped lower after condition (ankle: 4.3 cm; knee: 3.5 cm, p < 0.0001) but their jump heights returned to the baseline levels after 10-min post-joint cooling (p > 0.16). SJ heights did not change at any time interval (F_8,280 = 1.67; p = 0.11).

Bilateral joint cooling does not produce a facilitatory effect during a high-intensity dynamic movement. Cryotherapy at the lower extremity joints should be done ten minutes before games or practices to avoid a performance deficit in vertical jump heights.

Tendons show morphological and vascular adaptations to mechanical loadings.

To measure and compare the features of regional microcirculation within the supraspinatus tendon, and to investigate the correlations between those features and shoulder strength in overhead athletes.

Seventeen badminton athletes were recruited. DCE-MRI was conducted on the tendons in each athlete's dominant arm, including measures for the volume transfer constant (K ^trans ), reverse reflux rate constant(K_ep) and the extravascular extracellular space volume (V_e). Isokinetic tests were used to measure the acceleration time and the relative fatigue ratio of the shoulder external rotation of the arm.

The DCE-MRI measures for the anterior, posterior, and entirety of the tendon showed regional differences and correlations between the K_ep values for the whole supraspinatus tendon and the acceleration time (r = -0.663, p= 0.005) and between the V_p value of the whole tendon and the relative fatigue ratio (r = -0.605, p= 0.01).

There are differences in the microcirculatory features of the anterior and posterior portions of the supraspinatus tendon. In addition, microcirculation at the supraspinatus tendon and shoulder external rotation explosive strength and fatigue are correlated.

Isokinetic eccentric cycling is increasingly being utilised to examine the effect of chronic eccentric muscle training however little is known about how individuals familiarise to such a unique training modality.

To examine longitudinal variation in power output and lower limb muscle activation during familiarisation to maximal recumbent isokinetic eccentric cycling.

Twelve male volunteers, unfamiliar with eccentric cycling, completed four trials, separated by 7-10 days, each comprising 6 × 10 s maximal isokinetic eccentric efforts between 20-120 rpm. Peak power and average power output (PO), and surface electromyography (sEMG) of therectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), and medial gastrocnemius (MG) were recorded throughout. Systematic error across repeated trials was assessed using one-way ANOVA, and random error quantified using coefficient of variation (CV, %).

Average PO at 60 rpm and RF activation at 20 rpm increased from trial 1-2 (p < 0.05), with no other systematic error between trials at any cadence. Across all cadences, the CV for peak PO (∼ 13%), average PO (∼ 10%), VL activation (∼ 13%) and RF activation(∼ 19%) was moderate and plateaued after one familiarisation (i.e. T2-T3). However, for BF (∼ 24%) and MG (∼ 22%) activation reliability was generally poor. For the majority of variables the reliability was best at 60 rpm.

Therefore, with one familiarisation, 60 rpm is recommended to achieve moderate between-session reliability in the measurement of power output and lower limb muscle activation during recumbent, eccentric cycling.

The moment generated by a muscle is influenced, among other factors, by the angular velocity and the testing position. However, the effect of these factors on hip muscles' agonist/antagonist ratios is not well understood. The main purpose of this study was to analyze this effect in a group of apparently healthy women and men.

Sixteen women and 24 men, aged 21-25 years participated in this study. The isokinetic concentric hip flexor/extensor (F/E) and adductor/abductor (AD/AB) strength ratios were calculated based on testing in supine and standing positions for the flexors and extensors) and side-lying and standing positions (for the adductors and abductors) tested at 60 and 180°/s.

For both genders the isokinetic moment of hip muscles decreased with increased angular velocity and the highest moments were observed in standing position. A significant interaction of position, angular velocity, and gender was observed (p < 0.05), which indicated that men experienced greater increases in F/E and AD/AB ratios in standing position at 180°, whereas women demonstrated lower ratios in the same position.

Isokinetic tests of the hip muscles ratios: F/E and AD/AB in standing and in sitting indicate that the test position and gender have a significant effect on the test findings.

In subjects with chronic ankle instability (CAI), balance and functionality have been evaluated to determine the stability of the ankle, but there is limited evidence about relationships between these variables with active (AJR) and passive (PJR) isokinetic joint repositioning.

To determine the correlation between isokinetic joint repositioning, static balance, dynamic balance and a self-reported questionnaire in CAI participants.

Twenty subjects with unilateral CAI participated. AJR, PJR, average velocity (AV), average radius (AR), Modified Star Excursion Balance Test (SEBT) and Identification of Functional Ankle Instability were measured.

The principal correlations were between the AJR of the affected ankle and the bilateral static balance [AV (r = -0.74, R²= 0.55, p = 0.005) and AR (r = -0.73, R² = 0.53, p = 0.006)]. A correlation between the PJR of the non-affected ankle with the SEBT of non-affected ankle in a posterolateral direction (r = -0.67, R²= 0.45, p = 0.017) was observed.

Strong relationships were seen between the AJR of the affected ankle and the bilateral static balance. In standing position, the non-affected ankle could mask the altered proprioception and balance.

Pre-exercise stretching is a commonly used practice by many competitive and recreational athletes. However, the effects of stretching on muscle performance are still incongruous. Furthermore, there is conflicting evidence regarding the intensity of stretching and the effect it has on muscular strength.

To investigate the effects of two different intensity levels of passive static stretching protocols on concentric knee extension strength.

Twenty-two male recreational athletes involved in regular resistance training programs were evaluated using a randomized design. Subjects performed an isokinetic test of the knee extensors following either maximal intensity static stretching, submaximal intensity static stretching, or no stretching.

The only significant difference in the peak moment, amounting to 10.5%, was noted between maximal intensity stretching and no stretching.

Maximal intensity stretching of the quadriceps may adversely affect the acute concentric moment production capacity of these muscles.

The Achilles tendon (AT) requires optimal material and mechanical properties to function properly. Calculation of these properties depends on accurate measurement of input parameters (i.e. tendon elongation). However, the measurement of AT elongation with ultrasound during maximum voluntary isometric contraction (MVIC) is overestimated by ankle joint rotation (AJR). Methods to correct the influence of this rotation on AT elongation exist, yet their reproducibility in clinical settings is unknown.

To evaluate the test-retest reproducibility of AT elongation during MVIC after AJR correction.

Ten participants attended test and retest measurements where they performed plantar-flexion MVIC on a dynamometer. Simultaneously, ultrasound recorded AT elongation as the displacement of the medial gastrocnemius-myotendinous junction, while an electrogoniometer measured AJR. The ankle was then passively rotated to the AJR achieved during MVIC and AT elongation again determined. Elongation was corrected by subtracting this passive AT elongation from the total AT elongation during MVIC. Reproducibility was evaluated using ICC (2.1), test-retest variability (TRV, %), Bland-Altman analyses (Bias ± LoA [1.96*SD]) and standard error of the measurement (SEM).

Corrected AT elongation reproducibility exhibited an ICC = 0.79, SEM = 0.2 cm and TRV = 20 ± 19%. Bias ± LoA were determined to be 0.0 ± 0.8 cm.

Using this ultrasound and electrogoniometer-based method, corrected AT elongation can be assessed reproducibly.

Tart cherry juice contains a high level of antioxidant and anti-inflammatory phytonutrients. Limited research has investigated its potential to ameliorate symptoms of delayed onset muscle soreness (DOMS) caused by inflammation from eccentric exercise.

The purpose of investigation was to assess the effect of a tart cherry beverage (TCB) on delayed onset muscle soreness (DOMS).

Participants underwent assessment of the quadriceps for pain, muscle tenderness, thigh girth, flexibility, strength, and markers of muscle inflammation and damage at baseline, immediately following, and 24 h, 48 h, 96 h, and one week post-eccentric fatigue protocol while consuming TCB(N = 15) or placebo (N = 14). Two-way mixed ANOVA assessed the effects of time, group, and interaction for all variables except pain, which was assessed using Wilcoxon rank sum tests (p < 0.05).

No significant main effect of group and no significant interaction was demonstrated between group and time, but a significant main effect of time was revealed for thigh girth, tenderness, flexibility, and strength (p < 0.001-0.003). For pain, change over time from baseline to post-fatigue was higher in the TCB group (p= 0.008). No statistically significant main effect of time, group, or interaction effect between time and group was demonstrated for cytokine data.

Results from this study provide important insights to methodological issues that will guide future studies using TCB including, dose of anthocyanins, muscle groups to study, fatigue protocols to use and length of supplementation.

The effects of stretch-shortening cycle (SSC) training are well-described in the literature but the mechanism of how it changes the characteristics of the SSC moment-time curve and contraction velocity is unknown.

The purpose of the present study was to investigate the adaptation mechanisms of the knee extensor contractile properties in response to a short-term unilateral SSC exercise training.

Twenty-four subjects (22.9 ± 2.4 years) were randomised to an experimental or control group. A custom-built dynamometer was used to test the mechanical properties of the quadriceps muscle. Each subject participated in the pre-, and post-test session. Subjects in the experimental group participated in nine training sessions and performed maximal voluntary stretch-shortening cycle contractions on the dynamometer. Changes in the knee extensor contractile properties were measured from an SSC curve.

Multivariate analysis of variance (MANOVA) revealed a significant multivariate effect for the measured variables in relation to group assignment. SSC exercise training significantly changed concentric moment(M_{CC}, F_{1,22} = 96.2, p = 0.000), and contraction velocity(F_{1,22} = 125.6, p = 0.000) resulting in a 29.6% improvement in concentric peak angular velocity (ω). Stepwise multiple regression analysis showed that ω was significantly predicted only by M_{CC}(r = 0.751, p = 0.005).

Short-term unilateral SSC exercise training modifies the characteristics of the SSC moment-time curve and contraction velocity through the mechanical adaptation of the knee extensor contractile properties.

To compare the expression of C-C Chemokine receptor type 5 (CCr5) on monocytes and T cells in soccer players who were submitted to isokinetic concentric or eccentric exercise.

Fourteen male athletes from the U-20 soccer category of a first division Brazilian soccer team (ages 17.75 ± 1.21 years) were randomized into concentric exercise (CON, n = 7) or eccentric (ECC, n = 7) isokinetic exercise groups. The peripheral frequency of CD3+ CCR5 and CD14+ CCR5+ was evaluated before, immediately after, and 24 h after each exercise bout using flow cytometry.

Progressive decreases were found in total CCr5 in ECC groups, with significant differences between baseline and 24 h after(p = 0.023). Both ECC and CON groups induced a significant decrease in CCr5 expression on the cell surface of CD14+ monocytes 24 h after bout(p < 0.05), with the ECC exercise associated with a more pronounced decrease(p < 0.05). In CD3+ T cells, CCr5 expression increased immediately after ECC but not in the CON exercise, returning to baseline values 24 h after(p < 0.05).

CCr5 is highly sensitive to physical exercise and the modulation of its expression on cell surface may be related to migration of the cells to damaged tissue.