Neural and muscular contributions to the age-related loss in power of the knee extensors in men and women.

The mechanisms for the loss in limb muscle power in old (60-79 years) and very old (≥80 years) adults and whether the mechanisms differ between men and women are not well-understood. We compared maximal power of the knee extensor muscles between young, old, and very old men and women and identified the neural and muscular factors contributing to the age-related loss of power. 31 young (22.9±3.0 years, 15 women), 83 old (70.4±4.9 years, 39 women), and 16 very old adults (85.8±4.2 years, 9 women) performed maximal isokinetic contractions at 14 different velocities (30-450°/s) to identify peak power. Voluntary activation (VA) and contractile properties were assessed with transcranial magnetic stimulation to the motor cortex and electrical stimulation of the femoral nerve. The age-related loss in power was ~6.5 W·year-1 for men (R2=0.62, p<0.001), which was a greater rate of decline (p=0.002) than the ~4.2 W·year-1 for women (R2=0.77, p<0.001). Contractile properties were the most closely associated variables with power output for both sexes, such as the rate of torque development of the potentiated twitch (men: R2=0.69, p<0.001; women: R2=0.57, p<0.001). VA was weakly associated with power in women (R2=0.13, p=0.012) but not men (p=0.191), whereas neuromuscular activation (EMG amplitude) during the maximal power contraction was not associated with power in men (p=0.347) or women (p=0.106). These data suggest that the age-related loss in power of the knee extensor muscles is due primarily to factors within the muscle for both sexes, although neural factors may play a minor role in older women.

Physical Therapy Provider Continuity Predicts Functional Improvements in Inpatient Rehabilitation.

BACKGROUND AND PURPOSE: Health care continuity has been linked to improved patient outcomes in a variety of professions and settings. Patients in inpatient rehabilitation receive a consistent dosage of physical therapy (PT) treatment; however, the providing physical therapist may vary. Despite the potential influence of PT provider continuity on functional outcomes in the inpatient rehabilitation setting, this association has not yet been studied. METHODS: An observational retrospective chart review was conducted on 555 discharged inpatient rehabilitation patients. The relationship between the number of PT providers from whom a patient received care and Quality Indicator (QI) Mobility discharge scores was examined with Pearson product-moment correlation coefficients, initially with the entire patient group and secondarily with distinct diagnostic groups. Data from subgroups for whom a significant relationship was established were then included in a hierarchical linear regression analysis accounting for relevant covariates. RESULTS: The number of PT providers correlated negatively with QI Mobility discharge scores ( r = -0.41, P ≤ 0.001). When controlling for QI Mobility admission scores, the "Stroke" (partial r = -0.17, P = 0.02), "Spinal Cord Injury" (partial r = -0.28, P = 0.002), and "Other Neuromuscular" (partial r = -0.35, P = 0.03) groups demonstrated significant inverse relationships. A hierarchical linear regression incorporating these 3 diagnostic groups revealed that the number of PT providers remained a significant predictor of QI Mobility discharge scores ( B = -1.50, P ≤ 0.001) when accounting for covariates. DISCUSSION AND CONCLUSIONS: PT provider continuity is related to the functional improvement of neurologically impaired patients in inpatient rehabilitation.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A405 , which discusses the findings of this work in a narrative format).

Neutralization Assay with SARS-CoV-1 and SARS-CoV-2 Spike Pseudotyped Murine Leukemia Virions

Antibody neutralization is an important prognostic factor in many viral diseases. To easily and rapidly measure titers of neutralizing antibodies in serum or plasma, we developed pseudovirion particles composed of the spike glycoprotein of SARS-CoV-2 incorporated onto murine leukemia virus capsids and a modified minimal MLV genome encoding firefly luciferase. These pseudovirions provide a practical means of assessing immune responses under laboratory conditions consistent with biocontainment level 2.

Recurrent Paenibacillus infection.

The genus Paenibacillus includes Gram-positive bacteria that are rarely known to cause infection in humans. Here we report a case of recurrent Paenibacillus macerans infection in an otherwise healthy 66-year-old man following environmental exposure decades prior to presentation to our clinic. Despite numerous attempts at surgical debridement, Paenibacillus was repeatedly cultured from the soft tissue of the lower extremity wound site over a period of years. Post-operative antibiotic treatment prevented recurrence; however, upon antibiotic discontinuation, Paenibacillus was again cultured from the wound. After multiple rounds of debridement and antibiotic therapy, the patient was started on indefinite, low-dose trimethoprim-sulfamethoxazole therapy to suppress infection resulting from transition of Paenibacillus spores to vegetative cells. This case adds to the limited number of case reports describing Paenibacillus species infection in healthy adults and presents a unique case of bona fide P. macerans infection requiring life-long antibiotic therapy.