Increasing Physical Activity Through Principles of Habit Formation in New Gym Members: a Randomized Controlled Trial

Background

The promotion of physical activity (PA) is paramount to public health, yet interventions in the social cognitive tradition have yielded negligible improvements. The limited progression may be due to an overreliance on intention as the proximal determinant of behavior and a lack of consideration of implicit/automatic processes. The purpose of this study was to examine the impact of a habit formation intervention on PA over 8 weeks in a two-arm parallel design, randomized controlled trial.

Methods

Participants (n = 94) were new gym members with the intention to engage in PA but below international PA guidelines at baseline, who were randomized into a control or habit experimental group. The experimental group attended a workshop (at baseline) and received a follow-up booster phone call at week 4. The primary outcome of the study was minutes of moderate-vigorous intensity PA (MVPA) at week 8. The secondary outcome was a manipulation check to determine if the experimental group effectively incorporated habit-building constructs (cues and practice consistency).

Results

The experimental group showed a significant increase in MVPA after 8 weeks in both accelerometry (d = 0.39, p = .04) and self-report (d = 0.53, p = .01) compared with the control group. The experimental group also showed an increase in use of cues (d = 0.56, p < .001) and practice consistency (d = 0.40, p = .01) at week 8.

Conclusion

The results contribute to the initial validity of increasing PA through a focus on preparation cues and practice consistency. Future research should replicate these findings and extend the duration of assessment to evaluate whether PA changes are sustained. Registered Trial Number NCT02785107

     

Composition of perineuronal nets in the adult rat cerebellum and the cellular origin of their components

The decrease in plasticity that occurs in the central nervous system during postnatal development is accompanied by the appearance of perineuronal nets (PNNs) around the cell body and dendrites of many classes of neuron. These structures are composed of extracellular matrix molecules, such as chondroitin sulfate proteoglycans (CSPGs), hyaluronan (HA), tenascin-R, and link proteins. To elucidate the role played by neurons and glial cells in constructing PNNs, we studied the expression of PNN components in the adult rat cerebellum by immunohistochemistry and in situ hybridization. In the deep cerebellar nuclei, only large excitatory neurons were surrounded by nets, which contained the CSPGs aggrecan, neurocan, brevican, versican, and phosphacan, along with tenascin-R and HA. Whereas both net-bearing neurons and glial cells were the sources of CSPGs and tenascin-R, only the neurons expressed the mRNA for HA synthases (HASs), cartilage link protein, and link protein Bral2. In the cerebellar cortex, Golgi neurons possessed PNNs and also synthesized HASs, cartilage link protein, and Bral2 mRNAs. To see whether HA might link PNNs to the neuronal cell surface by binding to a receptor, we investigated the expression of the HA receptors CD44, RHAMM, and LYVE-1. No immunolabelling for HA receptors on the membrane of net-bearing neurons was found. We therefore propose that HASs, which can retain HA on the cell surface, may act as a link between PNNs and neurons. Thus, HAS and link proteins might be key molecules for PNN formation and stability.     

Rat estrous cycle influences the sexual diergism of HPA axis stimulation by nicotine

We previously reported that female rats had significantly greater hypothalamic-pituitary-adrenal (HPA) axis responses to cholinergic stimulation by nicotine (NIC) than did male rats. Females in defined estrous cycle stages, however, were not studied because of sample size limitations. We further explored this finding by determining HPA axis responses to two doses of NIC in female rats (N = 101) during different estrous cycle stages, and in males (N = 69). NIC doses were: 0.3 mg/kg, which provided the greatest female-male difference in the earlier study, and 0.5 mg/kg, which stimulated the HPA axis similarly in the two sexes. Plasma AVP, ACTH, and corticosterone were measured. Proestrous and estrous females had higher ACTH responses to NIC (0.3 mg/kg) compared to metestrous and diestrous females, and compared to males. ACTH responses to NIC (0.5 mg/kg) were similar, regardless of estrous cycle stage or sex. Males had higher AVP responses to both NIC doses compared to females in all estrous cycle stages. Corticosterone responses followed the ACTH responses, except that females in all estrous stages started from a higher corticosterone baseline compared to males. These results are similar to our earlier findings across the estrous cycle with non-specific cholinergic stimulation by physostigmine and suggest that the nicotinic system contributes to the differential HPA axis responses to cholinergic challenge across the estrous cycle.     

Motor Axonal Neuropathy During Treatment With Simvastatin

Simvastatin is a cholesterol-lowering drug that acts by inhibiting hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in cholesterol synthesis. Abnormal laboratory findings include transient increases in serum creatine kinase (CK) due to a myopathic syndrome. Rarely, neurological side effects include axonal sensory-motor peripheral neuropathy, characterized in some cases by a prevalent motor involvement accompanied by subclinical sensory damage. We report a case of purely motor axonal neuropathy associated with simvastatin. A 72-year-old woman, after five years of treatment with simvastatin, developed progressive weakness, cramps and fasciculations mainly involving proximal muscles in the lower limbs, though without sensory symptoms or signs. Deep reflexes were lost in the lower limbs. There was no sign of upper motor-neuron involvement. CK was elevated (up to 2000 U/l). EMG showed marked neurogenic damage with fibrillations and fasciculations in the lower limbs. ENG showed motor fiber loss within the lower limb nerves without involvement of sensory fibers. CSF examination was normal. Deltoid muscle biopsy showed neurogenic changes and some ragged-red fibers. One year after simvastatin withdrawal the patient's state of weakness improved and the cramps resolved. The CK level dropped to 700 U/l.     

A subcutaneous glucose sensor with improved longevity, dynamic range, and stability of calibration

OBJECTIVE: To evaluate the lifetime, response time, linearity, glucose range, and calibration stability of two different types of continuous glucose sensor implants in a dog model. RESEARCH DESIGN AND METHODS: Glucose sensors based on the enzyme electrode principle that are coupled to a radio transmitter were evaluated on the bench top, sterilized, and then implanted subcutaneously in nondiabetic mongrel dogs. A multichannel radio receiver and PC data processor were used to record the sensor glucose data. Initial early reliable sensor responsivity was recognized by a vigorous hyperglycemic excursion after an intramuscular injection of glucagon. Periodically the dogs were made temporarily diabetic by blocking pancreatic insulin secretion by subcutaneous injection of a synthetic somatostatin (octreotide). By using exogenous insulin injection followed by intravenous glucose infusion, glucose levels were manipulated through the entire clinical range of interest: 2.2-38.9 mmol/l (40-700 mg/dl). Every 5-10 min, reference blood glucose samples were obtained and run in our hospital clinical laboratory. The glucose sensor data was evaluated by linear least squares optimization and by the error grid method. RESULTS: Beginning as early as postimplant day 7, the in vivo performances of sensors were evaluated by using glucose infusion studies performed every 1-4 weeks. Bench-top and in vivo 90% response-time sensors were in the range of 4-7 min during sensor lifetime. Best-performing sensors from both types are summarized as follows. The earlier-stage technology was less linear with a dynamic range of no more than 22 mmol/l glucose, had a best-case recalibration interval of 18 days, and had a maximum lifetime of 94 days. The improved later-stage technology sensors, which were constructed with the addition of bioprotective and angiogenic membranes, were linear over the full extended range of clinical interest (2.2-38.9 mmol/l [40-700 mg/dl glucose]), had a best-case recalibration interval of 20 days, and had a maximum lifetime of >160 days. CONCLUSIONS: Stable clinically useful sensor performance was demonstrated as early as 7 days after implantation and for a sensor lifetime of 3-5 months. This type of subcutaneous glucose sensor appears to be promising as a continuous and painless long-term method for monitoring blood glucose. Specifically sensors with top-layer materials that stimulate angiogenesis at the sensor/tissue interface may have better dynamic measurement range, longer lifetimes, and better calibration stability than our previously reported sensors.     

Impact of low body weight on frequency of pediatric cardiac catheterization complications

The overall risk of pediatric cardiac catheterization remains low despite the enormous new complexity and potential for complications brought on by the growth of interventional catheterization techniques. For all patients aged < 21 years, balloon interventions carry the highest risk, diagnostic procedures carry more risk than non-balloon interventions, and although weight < or = 5 kg is a significant risk factor for complications, irrespective of the type of procedure performed, weight < or = 2.5 kg did not alter that risk.     

Maternal predictors of fetal demise in trauma during pregnancy

Trauma complicates 6 to 7 per cent of all pregnancies, but fetal demise secondary to maternal trauma occurs much less frequently. This study was done to analyze the incidence of fetal demise as a function of 21 maternal characteristics determined within the first 24 hours after trauma. Nine instances of fetal demise were identified from 73 pregnant patients with trauma admitted to four Level I trauma centers from a combined data base of 30,000 patients. Maternal factors examined by logistic regression were Injury Severity Score (ISS), Trauma Score (TS), Abbreviated Injury Scale (AIS), fluid requirements in the initial 24 hours, systolic blood pressure (SBP), heart rate (HR), hemoglobin, hematocrit and arterial blood gas analysis. Fetal demise was found to be associated with increasing ISS, increasing face and abdominal AIS, increasing fluid requirements, maternal acidosis and maternal hypoxia. Standard maternal laboratory and physiologic parameters, such as hemoglobin and hematocrit, oxygen and hemoglobin saturation, partial pressure of carbon dioxide, SBP and HR were not predictive. The TS was also found to be nonpredictive.