Post-dynamic Resistance Exercise Hypotension: Exploring Individual Responses and Predictors

Background: Post-dynamic resistance exercise hypotension (PREH) has been largely demonstrated. However, little is known regarding the interindividual variation of PREH magnitude and its predictors (i.e. factors of influence).Aims: To assess the interindividual variation of PREH and its predictors related to the characteristics of the individuals and the exercise protocol.Methods: This study retrospectively analysed data from 131 subjects included in seven controlled trials about PREH (including at least one dynamic resistance exercise and one control session) conducted by two research laboratories. The interindividual variation was assessed by the standard deviation of the individual responses (SDIR), and linear regression analyses were conducted to explore the predictors.Results: PREH showed moderate interindividual variation for systolic (SBP, SDIR=4.4mmHg; 0.35 standardised units) and diastolic blood pressures (DBP, SDIR=3.6mmHg; 0.32 standardised units). For systolic PREH, multivariate regression analysis (R2=0.069) revealed higher baseline SBP (B=−0.157, p=0.008) and higher number of sets (B=−3.910, p=0.041) as significant predictors. For diastolic PREH, multivariate regression analysis (R2=0.174) revealed higher baseline DBP (B=−0.191, p=0.001) and higher exercise volume (i.e. number of exercises *sets per exercise *repetitions per sets >150; B=−4.212, p=0.001) as significant predictors.Conclusion: PREH has a considerable interindividual variation. Greater PREH magnitude is observed in individuals with higher baseline blood pressure and after exercise protocols that comprehend higher number of sets and exercise volume.

Personality does not predict individual niche variation in a freshwater fish

Animal populations can exhibit considerable interindividual variation in both behavioral traits and niche use, but the potential connections between these characteristics are rarely compared for the same individuals. We aimed to test whether behavioral syndromes were predictive of individual diet or microhabitat in a native New Zealand freshwater fish, Gobiomorphus cotidianus. We carried out laboratory behavioral assays and repeated habitat and diet measurements in a seminatural mesocosm system. We found considerable repeatability in individual behavior, largely consistent with a proactive/reactive behavioral syndrome. We also found modest individual repeatability in microhabitat use and relatively strong individual specialization in diet. However, no measure of niche use in the mesocosms was significantly predicted by individual personality. Further studies of this type will be needed to assess whether links between individual behavior and resource use are more important in other species or ecological contexts.

Express yourself: bold individuals induce enhanced morphological defences

Organisms display an impressive array of defence strategies in nature. Inducible defences (changes in morphology and/or behaviour within a prey's lifetime) allow prey to decrease vulnerability to predators and avoid unnecessary costs of expression. Many studies report considerable interindividual variation in the degree to which inducible defences are expressed, yet what underlies this variation is poorly understood. Here, we show that individuals differing in a key personality trait also differ in the magnitude of morphological defence expression. Crucian carp showing risky behaviours (bold individuals) expressed a significantly greater morphological defence response when exposed to a natural enemy when compared with shy individuals. Furthermore, we show that fish of different personality types differ in their behavioural plasticity, with shy fish exhibiting greater absolute plasticity than bold fish. Our data suggest that individuals with bold personalities may be able to compensate for their risk-prone behavioural type by expressing enhanced morphological defences.

Increase of Urinary 5-Hydroxyindoleacetic Acid Excretion but Not Serum Chromogranin a Following Over-The-Counter 5-Hydroxytryptophan Intake

BACKGROUND: 5-hydroxyindoleacetic acid (5-HIAA) excretion is commonly measured for biochemical detection of carcinoid tumours. A 77-year-old woman was referred for elevated 24 h urine 5-HIAA excretion (510 μmol/day; normal is less than 45 μmol/day) and serum chromogranin A (CgA) (72.1 U/L; normal is less than 18 U/L), both subsequently normalized after discontinuation of 5-hydroxytryptophan (5-HTP). 5-HTP, a precursor of serotonin, is not commonly listed as a substance that increases 5-HIAA levels in urine. The effect of 5-HTP on CgA has not been previously described.OBJECTIVES: To determine whether, and to what extent, oral 5-HTP increases urine 5-HIAA excretion and serum CgA levels in healthy volunteers.PATIENTS AND METHODS: A randomized, prospective, double-blind, placebo-controlled crossover study, with a four-day washout period, was performed in a general community setting. Eight healthy subjects aged 22 to 58 years were recruited by advertising. Bedtime ingestion of 5-HTP 100 mg/day was compared with placebo ingestion for 10 days. Twenty-four hour urine excretion of 5-HIAA and serum CgA were the main outcome measures.RESULTS: Median (range) urinary 5-HIAA excretion was 204 μmol/day (22 μmol/day to 459 μmol/day) during 5-HTP intake, compared with 18 μmol/day (12 μmol/day to 36 μmol/day) during placebo intake (P=0.017). 5-HTP did not affect clinical symptoms or serum CgA levels.CONCLUSIONS: Oral 5-HTP increases urinary 5-HIAA excretion with considerable interindividual variation. In a small number of subjects, oral 5-HTP did not affect serum CgA levels. Therefore, increased 5-HIAA levels with normal CgA levels may suggest 5-HTP ingestion. The use of over-the-counter 5-HTP should be excluded as the cause of increased urinary 5-HIAA levels before initiating diagnostic tests to search for a carcinoid tumour. 5-HTP should be added to popular references as a substance that may cause increased 5-HIAA excretion.

Interindividual variation in hypoxic ventilatory response: potential role of carotid body

There is considerable interindividual variation in ventilatory response to hypoxia in humans but the mechanism remains unknown. To examine the potential contribution of variable peripheral chemorecptor function to variation in hypoxic ventilatory response (HVR), we compared the peripheral chemoreceptor and ventilatory response to hypoxia in 51 anesthetized cats. We found large interindividual differences in HVR spanning a sevenfold range. In 23 cats studied on two separate days, ventilatory measurements were correlated (r = 0.54, P less than 0.01), suggesting stable interindividual differences. Measurements during wakefulness and in anesthesia in nine cats showed that although anesthesia lowered the absolute HVR it had no influence on the range or the rank of the magnitude of the response of individuals in the group. We observed a positive correlation between ventilatory and carotid sinus nerve (CSN) responses to hypoxia measured during anesthesia in 51 cats (r = 0.63, P less than 0.001). To assess the translation of peripheral chemoreceptor activity into expiratory minute ventilation (VE) we used an index relating the increase of VE to the increase of CSN activity for a given hypoxic stimulus (delta VE/delta CSN). Comparison of this index for cats with lowest (n = 5, HVR A = 7.0 +/- 0.8) and cats with highest (n = 5, HVR A = 53.2 +/- 4.9) ventilatory responses showed similar efficiency of central translation (0.72 +/- 0.06 and 0.70 +/- 0.08, respectively). These results indicate that interindividual variation in HVR is associated with comparable variation in hypoxic sensitivity of carotid bodies. Thus differences in peripheral chemoreceptor sensitivity may contribute to interindividual variability of HVR.