Accuracy of the VO2peak prediction equation in firefighters

Background: A leading contributing factor to firefighter injury and death is lack of fitness. Therefore, the Fire Service Joint Labor Management Wellness-Fitness Initiative (WFI) was established that includes a focus on providing fitness assessments to all fire service personnel. The current fitness assessment includes a submaximal exercise test protocol and associated prediction equation to predict individual VO2peak as a measure of fitness. There is limited information on the accuracy, precision, and sources of error of this prediction equation. This study replicated previous research by validating the accuracy of the WFI VO2peak prediction equation for a group of firefighters and further examining potential sources of error for an individual firefighters’ assessment. Methods: The sample consisted of 22 firefighters who completed a maximal exercise test protocol similar to the WFI submaximal protocol, but the test was terminated when firefighters reached a maximal level of exertion (i.e., measured VO2peak). We then calculated the predicted VO2peak based on the WFI prediction equation along with individual firefighters’ body mass index (BMI) and 85% of maximum heart rate. The data were analyzed using paired samples t-tests in SPSS v. 21.0. Results: The difference between predicted and measured VO2peak was -0.77 ± 8.35 mL•kg-1•min-1. However, there was a weak, statistically non-significant association between measured VO2peak and predicted VO2peak (R2 = 0.09, F(1,21) = 2.05, p = 0.17). The intraclass correlation coefficient (ICC = 0.215, p > 0.05) and Pearson (r = 0.31, p = 0.17) and Spearman (ρ = 0.28, p = 0.21) correlation coefficients were small. The standard error of the estimate (SEE) was 8.5 mL•kg-1•min-1. Further, both age and baseline fitness level were associated with increased inaccuracy of the prediction equation. Conclusions: We provide data on the inaccuracy and sources of error for the WFI VO2peak prediction equation for predicting fitness level in individual firefighters, despite apparently accurate predictions for a group of firefighters. These results suggest that the WFI prediction equation may need to be reevaluated as a means of precisely determining fitness for individual firefighters, which may affect employment status, duty assignment, and overall life safety of the firefighter.This study was supported by a research grant from the Department of Homeland Security through a Federal Emergency Management Agency Assistance to Firefighters Grant (FEMA-AFG) (EMW-2010-FP-01606).Ope

Clinical Study Oxygen Cost of Walking in Persons with Multiple Sclerosis: Disability Matters, but Why?

Background. The oxygen cost (O 2 cost) of walking is elevated in persons with MS, particularly as a function of increasing disability status. Objective. The current study examined symptomatic (i.e., fatigue, pain, anxiety, and depression) and gait (i.e., velocity, cadence, and step length) variables that might explain why disability status is associated with O 2 cost of walking in persons with MS. Materials and Methods. 82 participants completed the Patient-Determined Disease Steps, Fatigue Severity Scale, McGill Pain Questionnaire, and Hospital Anxiety and Depression Scale and undertook 2 trials of walking on a GAITRite electronic walkway. Participants then completed a six-minute walk test with concurrent assessment of expired gases for quantifying oxygen consumption and O 2 cost of walking. Results. Disability ( = 0.55) as well as fatigue ( = 0.22), gait velocity ( = −0.62), cadence ( = −0.73), and step length ( = −0.53) were associated with the O 2 cost of walking. Cadence ( = −0.67), but not step length ( = −0.14) or fatigue ( = −0.10), explained the association between disability and the O 2 cost of walking. Conclusions. These results highlight cadence as a target of rehabilitation for increasing metabolic efficiency during walking among those with MS, particularly as a function of worsening disability

Egress Efficacy of Persons with Multiple Sclerosis During Simulated Evacuations

Expedited evacuation of commercial and residential structures in the event of an emergency may be more difficult for persons with physical movement disorders. There is a need to better characterize the impact of such disorders and provide movement data to improve evacuee and responder safety. We undertook a pilot, feasibility study that investigated the ability of persons with multiple sclerosis (MS) and controls without MS to walk along a 48 m long path that included five different door configurations with various opening hardware and closure mechanisms, both before and after a six-minute walk, simulating a long evacuation path. Persons with MS took longer to complete the evacuation circuit (102 vs. 31 s) and to pass through each door (average 4.8 vs. 1.4 s) compared to controls. During the six-minute walk, persons with MS had decreased walking speed (0.7 vs. 1.9 m/s). The MS population demonstrated more conservative gait biomechanics throughout the simulation, i.e., wider, shorter and slower steps. Timing and biomechanical differences between populations and the potential fatigue induced through an extended evacuation can be used to improve understanding of movement in populations with disabilities, and incorporate these data into estimation of flow rates during evacuation.Funding support for MB was provided by the National Science Foundation Engineering Research Center for Compact and Efficient Fluid Power (0540834), with additional support from the Foundation of the Consortium of Multiple Sclerosis Centers’ Multiple Sclerosis Workforce of the Future program.Ope

Oxygen Cost of Walking in Persons with Multiple Sclerosis: Disability Matters, but Why?

Background. The oxygen cost (O2 cost) of walking is elevated in persons with MS, particularly as a function of increasing disability status. Objective. The current study examined symptomatic (i.e., fatigue, pain, anxiety, and depression) and gait (i.e., velocity, cadence, and step length) variables that might explain why disability status is associated with O2 cost of walking in persons with MS. Materials and Methods. 82 participants completed the Patient-Determined Disease Steps, Fatigue Severity Scale, McGill Pain Questionnaire, and Hospital Anxiety and Depression Scale and undertook 2 trials of walking on a GAITRite electronic walkway. Participants then completed a six-minute walk test with concurrent assessment of expired gases for quantifying oxygen consumption and O2 cost of walking. Results. Disability (r=0.55) as well as fatigue (r=0.22), gait velocity (r=-0.62), cadence (r=-0.73), and step length (r=-0.53) were associated with the O2 cost of walking. Cadence (β=-0.67), but not step length (β=-0.14) or fatigue (β=-0.10), explained the association between disability and the O2 cost of walking. Conclusions. These results highlight cadence as a target of rehabilitation for increasing metabolic efficiency during walking among those with MS, particularly as a function of worsening disability

Mobility disability and the pattern of accelerometer-derived sedentary and physical activity behaviors in people with multiple sclerosis

Objective: Low physical activity and high sedentary behavior levels are major concerns in persons with multiple sclerosis (MS) and these differ depending on the level of mobility disability. However, the manner in which daily activity is accumulated is currently unknown in this population. Methods: A secondary analysis was performed on a combined data set of persons with MS from two previous investigations of physical activity and symptomatic or quality of life outcomes in the United States over a two year period (2007–2009). Mobility disability status was determined using the Patient Determined Disease Steps (PDDS) while activity behavior was objectively monitored using an ActiGraph accelerometer for 7 days. Results: Persons with MS who have mobility disability were involved in sedentary behavior, light and moderate intensity activity for 65%, 34% and 1% of the day, respectively compared to 60%, 37%, and 3%, respectively in those without mobility disability (p < 0.05). Breaks in sedentary time did not differ by mobility disability status. Compared to those without mobility disability, the average number of sedentary bouts longer than 30 min was greater in those with mobility disability (p = 0.016). Conclusion: Persons with MS with mobility disability are less active, engage in more sedentary behavior and accumulate prolonged sedentary bouts

Objectively Measured Physical Activity Is Associated with Brain Volumetric Measurements in Multiple Sclerosis

Background. Little is known about physical activity and its association with volumes of whole brain gray matter and white matter and deep gray matter structures in persons with multiple sclerosis (MS). Purpose. This study examined the association between levels of physical activity and brain volumetric measures from magnetic resonance imaging (MRI) in MS. Method. 39 persons with MS wore an accelerometer for a 7-day period and underwent a brain MRI. Normalized GM volume (NGMV), normalized WM volume (NWMV), and deep GM structures were calculated from 3D T1-weighted structural brain images. We conducted partial correlations (pr) controlling for demographic and clinical variables. Results. Moderate-to-vigorous physical activity (MVPA) was significantly associated with NGMV (pr=0.370, p<0.05), NWMV (pr=0.433, p<0.01), hippocampus (pr=0.499, p<0.01), thalamus (pr=0.380, p<0.05), caudate (pr=0.539, p<0.01), putamen (pr=0.369, p<0.05), and pallidum (pr=0.498, p<0.01) volumes, when controlling for sex, age, clinical course of MS, and Expanded Disability Status Scale score. There were no associations between sedentary and light physical activity with MRI outcomes. Conclusion. Our results provide the first evidence that MVPA is associated with volumes of whole brain GM and WM and deep GM structures that are involved in motor and cognitive functions in MS

Effects of exercise in a relapsing-remitting model of experimental autoimmune encephalomyelitis

Previous research has examined the effects of exercise in experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis. However, all previous studies have utilized a chronic model of EAE, with exercise delivered prior to or immediately after induction of EAE. To our knowledge, no study has examined the effects of exercise delivered during a remission period after initial disease onset in a relapsing-remitting model of EAE (RR-EAE). The current study examines the effects of both voluntary wheel running and forced treadmill exercise on clinical disability and hippocampal brain-derived neurotrophic factor (BDNF) in SJL mice with RR-EAE. The results demonstrate no significant effects of exercise delivered during remission after initial disease onset on clinical disability scores or levels of hippocampal BDNF in mice with RR-EAE. Furthermore, our results demonstrate no significant increase in citrate synthase activity in the gastrocnemius and soleus muscles of mice in the running wheel or treadmill conditions compared with the sedentary condition. These results suggest that the exercise stimuli might have been insufficient to elicit differences in clinical disability or hippocampal BDNF among treatment conditions. © 2016 Wiley Periodicals, Inc

A modified SCBA facepiece for accurate metabolic data collection from firefighters

<div><p>To better assess the energy expenditure and exertion of firefighters during simulated firefighting activities, a commercial firefighter self-contained breathing apparatus (SCBA) facepiece was modified to interface with a portable metabolic monitoring device (Cosmed K4b²) while still functioning as a positive pressure SCBA air supply. To validate the device, standard National Fire Protection Association 1981 SCBA function tests were conducted and 14 subjects performed variable-workload assessments using all combinations of two test devices (Cosmed K4b² and metabolic cart) and two masks (modified SCBA facepiece and stock manufacturer-supplied breath collection). Metabolic data collected with the Cosmed K4b² via the modified facepiece were found to be accurate when compared to a ParvoMedics Truemax 2400 metabolic cart (average per cent difference: 4.6%). This modified facepiece design is suitable for use in metabolic studies requiring the utilisation of an SCBA system. Furthermore, the well-established overestimation of oxygen consumption from the Cosmed K4b² system was replicated.</p></div