Clinical Physiology and Functional Imaging 

About: Clinical Physiology and Functional Imaging is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Blood pressure & Medicine. It has an ISSN identifier of 1475-0961. Over the lifetime, 1503 publications have been published receiving 30989 citations. The journal is also known as: Clin Physiol Funct Imaging.

Effect of a vibration exposure on muscular performance and body balance. Randomized cross-over study

Abstract: Summary This randomized cross-over study was designed to investigate the effects of a 4-min vibration bout on muscle performance and body balance in young, healthy subjects. Sixteen volunteers (eight men, eight women, age 24‐33 years) underwent both the 4-min vibration- and sham-interventions in a randomized order on different days. Six performance tests (stability platform, grip strength, isometric extension strength of lower extremities, tandem-walk, vertical jump and shuttle run) were performed 10 min before (baseline), and 2 and 60 min after the intervention. The effect of vibration on the surface electromyography (EMG) of soleus, gastrocnemius and vastus lateralis muscles was also investigated. The vibration-loading, based on a tilting platform, induced a transient (significant at the 2-min test) 2AE5% net benefit in the jump height (Pa 0AE019), 3AE2% benefit in the isometric extension strength of lower extremities (Pa 0AE020) and 15AE7% improvement in the body balance (Pa 0AE049). In the other 2-min or in the 60-min tests, there were no statistically significant differences between the vibration- and sham-interventions. Decreased mean power frequency in EMG of all muscles during the vibration indicated evolving muscle fatigue, while the root mean square voltage of EMG signal increased in calf muscles. We have shown in this study that a single bout of whole body vibration transiently improves muscle performance of lower extremities and body balance in young healthy adults.

Acute changes in neuromuscular excitability after exhaustive whole body vibration exercise as compared to exhaustion by squatting exercise

Abstract: Summary The effects of hard squatting exercise with (VbX+) and without (VbX)) vibration on neuromuscular function were tested in 19 healthy young volunteers. Before and after the exercise, three different tests were performed: maximum serial jumping for 30 s, electromyography during isometric knee extension at 70% of the maximum voluntary torque, and the quantitative analysis of the patellar tendon reflex. Between VbX+ and VbX) values, there was no difference found under baseline conditions. Time to exhaustion was significantly shorter in VbX+ than in VbX) (349 ± 338 s versus 515 ± 338 s), but blood lactate (5AE49 ± 2AE73 mmol l )1 versus 5AE00 ± 2AE26 mmol l )1 ) and subjectively perceived exertion (rate of perceived exertion values 18AE 1±1 AE2 versus 18AE 6±1 AE6) at the termination of exercise indicate comparable levels of fatigue. After the exercise, comparable effects were observed on jump height, ground contact time, and isometric torque. The vastus lateralis mean frequency during isometric torque, however, was higher after VbX+ than after VbX). Likewise, the tendon reflex amplitude was significantly greater after VbX+ than after VbX) (4AE34 ± 3AE63 Nm versus 1AE68 ± 1AE32 Nm). It is followed that in exercise unto comparable degrees of exhaustion and muscular fatigue, superimposed 26 Hz vibration appears to elicit an alteration in neuromuscular recruitment patterns, which apparently enhance neuromuscular excitability. Possibly, this effect may be exploited for the design of future training regimes.

Decrease in heart rate variability with overtraining: assessment by the Poincaré plot analysis.

Abstract: Numerous symptoms have been associated with the overtraining syndrome (OT), including changes in autonomic function. Heart rate variability (HRV) provides non-invasive data about the autonomic regulation of heart rate in real-life conditions. The aims of the study were to: (i) characterize the HRV profile of seven athletes (OA) diagnosed as suffering of OT, compared with eight healthy sedentary (C) and eight trained (T) subjects during supine rest and 60 degrees upright, and (ii) compare the traditional time- and frequency-domain analysis assessment of HRV with the non-linear Poincare plot analysis. In the latter each R-R interval is plotted as a function of the previous one, and the standard deviations of the instantaneous (SD1) and long-term R-R interval variability are calculated. Total power was higher in T than in C and OA both in supine (1158 +/- 1137, 6092 +/- 3554 and 2970 +/- 2947 ms2 for C, T and OA, respectively) and in upright (640 +/- 499, 1814 +/- 806 and 1092 +/- 712 ms2 for C, T and OA, respectively; P<0.05) positions. In supine position, indicators of parasympathetic activity to the sinus node were higher in T compared with C and OA (high-frequency power: 419.1 +/- 381.2, 1105.3 +/- 781.4 and 463.7 +/- 715.8 ms2 for C, T and OA, respectively; P<0.05; SD1: 29.5 +/- 18.5, 75.2 +/- 17.2 and 37.6 +/- 27.5 for C, T and OA, respectively; P<0.05). OA had a marked predominance of sympathetic activity regardless of the position (LF/HF were 0.47 +/- 0.35, 0.47 +/- 0.50 and 3.96 +/- 5.71 in supine position for C, T and OA, respectively, and 2.09 +/- 2.17, 7.22 +/- 6.82 and 12.04 +/- 10.36 in upright position for C, T and OA, respectively). The changes in HRV indexes induced by the upright posture were greater in T than in OA. The shape of the Poincare plots allowed the distinction between the three groups, with wide and narrow shapes in T and OA, respectively, compared with C. As Poincare plot parameters are easy to compute and associated with the 'width' of the scatter gram, they corroborate the traditional time- and frequency-domain analysis. We suggest that they could be used to indicate fatigue and/or prevent OT.

Is muscle power output a key factor in the age-related decline in physical performance? A comparison of muscle cross section, chair-rising test and jumping power

Abstract: Ageing compromises locomotor capacity and is associated with an increased risk of falls. Several lines of evidence indicate that both changes in muscle mass and performance are causative. Most studies, however, do not discern between effects of ageing, sedentarism and comorbidity. The present study compares the age effects in muscle cross section, force and power in physically competent self-selected subjects of different age groups. A total of 169 women and 89 men between 18 and 88 years, without any disease, impairment or medication affecting the musculoskeletal system were enrolled in this study. Calf muscle cross-sectional area was assessed by computed tomography. Muscle force and power were assessed by jumping mechanography. No significant correlation between muscle cross section and age was found in the men. A weak correlation in the women disappeared after correction for height. Close correlations with age, however, were found for peak force and peak power. Correction for muscle cross section or body weight further increased these correlation coefficients, particularly for peak power specific to body weight (r = 0.81 in women and r = 0.86 in men). The non-sedentarian population investigated here depicted a reduction of >50% between the age of 20 and 80 without a reduction in muscle cross section. This suggests a crucial role for muscular power in the ageing process. Possibly, the jumping mechanography as a measurement of anti-gravitational power output is a promising extension of the chair-rising test, known to be predictive for immobilization and the risk of falls.

Reliability of isokinetic strength imbalance ratios measured using the Cybex NORM dynamometer.

Abstract: The main aim of this study was to examine the absolute and relative reliability of some commonly used strength imbalance indices such as concentric hamstring-to-concentric quadriceps ratio, eccentric hamstring-to-concentric quadriceps ratio and bilateral concentric and eccentric strength ratios. An additional aim was to examine the reliability of the peak torque and work of the knee extensor and flexor muscles measured using the Cybex NORM dynamometer. Eighteen physically active healthy subjects (mean +/- standard deviation, age 23 +/- 3 years, height 176 +/- 5 cm, body mass 74 +/- 8 kg) were tested three times with 96 h between sessions. Peak torque, average work, unilateral and bilateral ratios were determined at 60, 120, 180 and -60 degrees s(-1). Low (0.34) to moderate (0.87) relative reliability (intraclass correlation coefficient, ICC) was found for strength imbalance ratios with eccentric hamstring-to-concentric quadriceps ratio showing the greater ICC (>0.80). High ICC values (0.90-0.98) were found for peak torque and average work. Absolute reliability (standard error of measurement) ranged from 3.2% to 8.7% for strength imbalance ratios and from 4.3% to 7.7% for peak torque and average work measurements. This study established the reliability of the most common strength imbalance ratios and of absolute isokinetic muscle strength assessed using the Cybex NORM.