Isokinetics and Exercise Science

Article withoout abstract.

This study was aimed to examine the impact of acute stretching on the rate of force development (RFD) of the plantar flexors (PF). Eleven physically active female subjects participated in the study. The right calf muscle-tendon unit was stretched during five passive cyclic slow stretches(5°/s) that consisted of a dynamic ascending stretch phase to a pre-determined final joint angle (80% of maximal dorsiflexion angle) and a 15∼s hold phase. Maximal isometric torque (MVC) of PF and dorsiflexors (DF) and the RFD of PF were determined before, immediately and 30min following stretching. Changes in passive stiffness, passive resistive torque and torque relaxation of PF were computed during stretching. Passive characteristics decreased significantly during stretching (−11 to −27%, P<0.01). DF MVC did not change following stretching but there was a significant decrease in PF MVC immediately and after 30 min of recovery (−10%, P< 0.001). In contrast, PF RFD remained unaltered following stretching (P>0.05). These results indicate that passive stretching (< 5 min) can be applied without altering the capacity to develop torque rapidly under isometric condition up to 75% of MVC despite significant MVC impairment. These findings may have practical implications for stretching undertaken during rehabilitation or sport training.

Article without abstract.

This study assessed the applicability of dynamometric muscle evaluation in scoliosis.

Objective: To assess the clinical applicability of the dynamometric muscle evaluation in scoliosis by reliability studies, its relations with the clinical measures, and comparison analysis with healthy subjects.

Methods: Thirty five scoliotic female patients and 27 healthy women were evaluated dynamometrically muscle strengths, additionally the scoliotic women were evaluated by clinical measures. To assess the reliability of isokinetic muscle testing 20 scoliotic women were tested twice 1 week apart

Results: The ICCs ranged 0.81–0.96, except in the case of the knee extensor strength at 120°/s. Curve angle was weakly correlated to trunk flexor strength at 90°/s (r=0.40), the curve pattern was moderately related to knee muscles' strengths (−0.46 < r < −0.57). Scoliotic women showed weaker isokinetic muscles strengths except the trunk extensors at 90°/s.

Conclusion: Isokinetic evaluation of trunk muscle strength may be an additional tool in assessing this patient group.

The aim of this study was to compare maximal isometric torque and EMG activity of neck flexors and extensors in flexed and extended positions between men and women. Twenty four non-trained young healthy subjects (12 men vs. 12 women) performed maximal isometric neck flexion and extension within 30° around the neutral position in a sitting posture using a modified isokinetic dynamometer. Surface EMG activity of sternocleidomastoid, scalenus, paraspinal and upper trapezius muscles was recorded bilaterally. Men exhibited higher normalized-to-lean body weight torque than women mainly during neck flexion (44%, P<0.001) compared to extension (18%, P<0.05). In addition, torque increased from extended to flexed positions in women only(+17%, P<0.001). This was associated with a decrease in EMG of neck extensors and upper trapezius muscles (from 35% to 20% and from 18% to 7%, P< 0.001, respectively) without changes in agonistic activity of neck flexors with neck position. In contrast, men displayed similar torque and muscle activation level within 30° of range of motion around the neutral position for both directions. These findings demonstrate gender-specific differences in neck function that was probably linked to higher coactivation level in antagonist muscles (neck extensors) and stabilizers (upper trapezius muscles).

Jumper's knee is a major reason of competition interruption for elite basketball players. This is due to the patellar tendinosis which explains knee pain and the decreased strength of knee extensors required for performing the jump. The aim of this study was to determine whether isokinetic parameters could identify competitive sportsmen who suffered from jumper's knee. The bilateral knee concentric strength of fifty seven elite basketball players was measured using a Cybex Norm isokinetic dynamometer at 60, 180 and 240°/s and during a longer test (15 × 180°/s). From this population, fifteen competitive basketball players with unilateral jumper's knee (Victorian Institute of Sport Assessment score: 62 ± 12) were compared with 42 control cases (VISA score: 93 ± 6). A knee extensors asymmetry at 60°/s of more than 10% identified the injured basketball players and represented the more useful parameter (probability of 66%). The fatigue isokinetic test at 180°/s was not informative. Injured athletes knee flexors strength was not different from the uninjured players. We conclude that concentric isokinetic evaluation of knee extensors at 60°/s indicate knee extensors torque asymmetry which may play a role in jumper's knee pathology.

Objective: The aim of this study was to determine if the diminished aerobic capacity of coronary artery disease (CAD) in male patients is accompanied by a peripheral impaired skeletal muscle function and to assess the correlation between the isokinetic strength and aerobic aptitude of these patients.

Materials and methods: Fifteen CAD patients and 15 healthy subjects(age: 60 ± 6 vs 57 ± 3.5 years old) performed both maximal exercise testing, an isokinetic assessment of knee muscles and a 6-minute walking test. The quadriceps and hamstrings were tested at 150 and 180°/s while being monitored with ECG. The cardio-respiratory and mechanical parameters (VO2, VT, HR, and power) were measured at ventilatory threshold and at maximal effort during a maximal exercise testing.

Results: Isokinetic assessment was conducted successfully with all patients. No rhythm irregularity or hemodynamic anomalies were observed in the 2 groups. Muscle testing revealed significant strength impairment. Quadriceps peak torque, at 150°/s was 77 ± 16 Nm in patients vs. 99 ± 23 Nm in controls, (p<0.01) while at 180°/s the values were 71 ± 14 vs. 91 ± 23 Nm, (p<0.01), respectively. For the hamstrings the values were respectively 49 ± 16 vs. 66 ± 14 Nm, (p <0.01) and 47± 10 vs. 60 ± 12 Nm, (p<0.01).

CAD subjects presented a deficient aerobic capacity compared to the healthy control group at maximal effort (Vo2 maximal uptake: Vo2 max: 20.34± 4.95 vs. 29.16 ± 7.68 ml mn $^{-1}$ kg $^{-1}$ , (p=0.01); maximal ventilation Ve max: 58.18 ± 16.28 vs 84 ± 24.45 ml mn ${-1}$ , (p<0.05); heart rate: HR max: 118 ± 21 vs 152 ± 13 beats mn $^{-1}$ , (p<0.001); maximal power: P max: 102 ± 31 vs. 153 ± 33 W. (p<0.001) and at ventilatory threshold: VT (Vo2: 13.77 ± 2.33 vs. 17.08 ± 3.59 ml mn $^{-1}$ kg $^{-1}$ , (p< 0.05); VE: 29.64± 6.64 vs. 37.76 ± 7.2 ml mn $^{-1}$ ,(p<0.05); HR: 86 ± 14 vs. 111 ± 15 beats mn $^{-1}$ , (p=0.001); but no significant difference was noticed for power (P: 61 ± 12 vs. 76 ± 24 W:). We also noticed that isokinetic muscle strength and O2 peak were not related to each other and are therefore independent.

Conclusion: This study shows that CAD patients, compared to healthy subjects, have impaired cardio respiratory capacities which are accompanied by increased muscle fatigability. Isokinetic muscle strength and maximal aerobic capacity are independent of each other. An isokinetic muscle assessment in these patients must be conducted systematically and seems to have a considerable value in cardiovascular rehabilitation.

Selected abstracts.