Influence of acute eccentric exercise on the H:Q ratio.

The purpose of the present study was to examine the effects of an acute bout of eccentric exercise on maximal isokinetic concentric peak torque (PT) of the leg flexors and extensors and the hamstrings-to-quadriceps (H:Q) strength ratio. Sixteen male (mean±SD: age=20.9±2 years; stature=177.0±4.4 cm; mass=76.8±10.0 kg) volunteers performed maximal, concentric isokinetic leg extension and flexion muscle actions at 60°·sec - 1 before and after (24-72 h) a bout of eccentric exercise. The eccentric exercise protocol consisted of 4 sets of 10 repetitions for the leg press, leg extension, and leg curl exercises at 120% of the concentric one repetition maximum (1-RM). The results indicated that the acute eccentric exercise protocol resulted in a significant (P<0.05) decrease in isokinetic leg flexion (13-19%) and leg extension (11-16%) PT 24-72 h post-exercise. However, the H:Q ratios were unaltered by the eccentric exercise protocol. These findings suggest that an acute bout of eccentric exercise utilizing both multi - and single - joint dynamic constant external resistance (DCER) exercises results in similar decreases in maximal isokinetic strength of the leg flexors and extensors, but does not alter the H:Q ratio.

The relationship between passive stiffness and evoked twitch properties: the influence of muscle CSA normalization.

Passive stiffness measurements are often used as a clinical tool to examine a muscle's passive lengthening characteristics. The purpose of this study was to examine the relationship between passive stiffness and evoked twitch properties prior to and following normalization of passive stiffness to muscle cross-sectional area (CSA). Ten healthy volunteers (mean ± SD age = 23 ± 3 year) performed passive range of motion, evoked twitch, and muscle CSA assessments of the plantar flexor muscles. Passive stiffness was determined from the slope of the final 5° of the angle-torque curve. Peak twitch torque (PTT) and rate of torque development (RTD) were determined via transcutaneous electrical stimulation, and muscle CSA was assessed using a peripheral quantitative computed tomography scanner. Pearson product moment correlation coefficients (r) were used to assess the relationships between passive stiffness and PTT and RTD and normalized passive stiffness (passive stiffness ⋅ muscle CSA(-1)) and PTT and RTD. Significant positive relationships were observed between passive stiffness and PTT (P = 0.003, r = 0.828) and RTD (P = 0.003, r = 0.825). There were no significant relationships between normalized passive stiffness and PTT (P = 0.290, r = 0.372) or RTD (P = 0.353, r = 0.329) demonstrating that stiffness did not account for a significant portion of the variance in twitch properties. Passive stiffness was largely influenced by the amount of muscle tissue in this study. Future studies that examine muscle stiffness and its relationship with performance measures, among different populations, and following various interventions may consider normalizing stiffness measurements to muscle CSA.

Wernicke-Korsakoff amnestic syndrome secondary to malnutrition in a patient with schizoaffective disorder.

OBJECTIVE: The authors identify a rare case of Wernicke-Korsakoff amnestic syndrome and highlight its occurrence in the absence of alcohol dependence. METHOD: A longitudinal case history of a patient with schizoaffective disorder who developed Wernicke-Korsakoff syndrome secondary to malnutrition. RESULTS: Refusal to eat based on persecutory delusions in chronic psychotic patients can cause malnutrition and result in Wernicke-Korsakoff syndrome. CONCLUSIONS: With increasing managed-care demands for outpatient treatment of chronic psychotic patients, physicians may see more cases of Wernicke-Korsakoff syndrome in psychiatric populations.

Fractal dimension and approximate entropy of heart period and heart rate: awake versus sleep differences and methodological issues.

1. Investigations that assess cardiac autonomic function include non-linear techniques such as fractal dimension and approximate entropy in addition to the common time and frequency domain measures of both heart period and heart rate. This article evaluates the differences in using heart rate versus heart period to estimate fractal dimensions and approximate entropies of these time series.2. Twenty-four-hour ECG was recorded in 23 normal subjects using Holter records. Time series of heart rate and heart period were analysed using fractal dimensions, approximate entropies and spectral analysis for the quantification of absolute and relative heart period variability in bands of ultra low (<0.0033 Hz), very low (0. 0033-0.04 Hz), low (0.04-0.15 Hz) and high (0.15-0.5 Hz) frequency.3. Linear detrending of the time series did not significantly change the fractal dimension or approximate entropy values. We found significant differences in the analyses using heart rate versus heart period between waking up and sleep conditions for fractal dimensions, approximate entropies and absolute spectral powers, especially for the power in the band of 0.0033-0.5 Hz. Log transformation of the data revealed identical fractal dimension values for both heart rate and heart period. Mean heart period correlated significantly better with fractal dimensions and approximate entropies of heart period than did corresponding heart rate measures.4. Studies using heart period measures should take the effect of mean heart period into account even for the analyses of fractal dimension and approximate entropy. As the sleep-awake differences in fractal dimensions and approximate entropies are different between heart rate and heart period, the results should be interpreted accordingly.

Decreased heart-period variability in patients with panic disorder: a study of Holter ECG records.

This study investigated cardiac autonomic function in patients with panic disorder and normal controls using Holter ECG records. A decrease in ultra-low frequency power (< 0.0033 Hz) is known to be associated with an increased risk for cardiovascular mortality in humans. Twenty-four-hour ECG was recorded in 29 patients with panic disorder and 23 normal controls using Holter records. Data for 20 h and also 20000 s of awake and 20000 s of sleep periods were analyzed using spectral analysis to quantify absolute and relative heart-period variability in ultra low (ULF: < 0.0033 Hz), very low (VLF: 0.0033-0.04 Hz), low (LF: 0.04-0.15 Hz) and high (HF: 0.15-0.5 Hz) frequency bands. The patients with panic disorder had significantly lower total and absolute ULF power, which was more pronounced during sleep. The patients also had significantly lower relative ULF power and significantly higher relative LF power during sleep. There was a significant increase of relative LF power from awake to sleep period only in the patient group. The decrease in total and ULF power may increase the risk of mortality and sudden arrhythmic death in patients with panic disorder if they experience a cardiac event. The higher relative LF power during sleep also suggests a possible higher sympathetic drive in the patients during sleep.

Effect of age on long-term heart rate variability.

OBJECTIVE: Previous studies on short-term time series of heart rage suggest an inverse relationship between age and spectral powers of heart rate variability in various frequency bands. In this study, we examined the relationship between age (6-61 years) and long-term heart rate variability. METHODS: We obtained 24-h Holter ECG in 33 healthy human subjects (11 children and 22 adults). The heart rate data were analyzed by using spectral analysis and fractal dimensions of the time series. RESULTS: We found a significant negative correlation between age and very low frequency (VLF, 0.0033-0.04 Hz), low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.5 Hz) powers and fractal dimensions during awake as well as sleep periods, and a positive correlation between age and LF/HF ratios. Age and ultra-low frequency (ULF, < 0.0033 Hz) were modestly and negatively correlated only during the awake period. CONCLUSIONS: Sleep ULF power is not significantly affected by age, whereas VLF, LF and HF powers and fractal dimensions of heart rate significantly decrease with age during awake as well as sleep periods.

Analysis of 24-hour ECG in patients with panic disorder.

Previous evidence suggests an increased cardiovascular morbidity in patients with panic disorder. In this study, we compared 24-hour ECG in patients with panic disorder (n = 22; age: 36.1 +/- 7.6 years) and healthy controls (n = 21; age: 34.6 +/- 10.0 years). The QTc intervals during the day or night were not significantly different between patients and controls. Ventricular ectopic beats were also not significantly different between the two groups. These results do not suggest any overt cardiac arrhythmias in this age group of patients with panic disorder.