The impact of inter-limb leg lean tissue mass asymmetry on stair climb performance in career firefighters.

The purpose of this study was to examine the influence of inter-limb leg lean tissue mass (LTM) asymmetry on stair climb (SC) performance in firefighters. Forty-one career firefighters (age = 32.3 ± 8.2 years, body mass = 92.1 ± 18.6 kg, stature = 178.3 ± 7.9 cm) visited the laboratory on one occasion and completed a whole body and leg composition assessment followed by a timed and weighted SC task. Percent body fat (%BF) and leg LTM were determined during a DEXA scan and regional thigh analysis. Asymmetry was assessed by the percent difference between limbs (dominant limb LTM - non-dominant limb LTM)/dominant limb LTM × 100) and a ± 3% cut-off for asymmetry classification. Participants ascended and descended 26 stairs four times as quickly as possible while wearing a weighted (22 kg) vest. Point biserial correlations were used to assess the relationship of inter-limb leg LTM asymmetry and SC performance before and after controlling for age and %BF. Results indicated that inter-limb leg LTM asymmetry was associated with longer SC task time (poorer performance) both before (r = 0.432, P = 0.005) and after (r = 0.502, P = 0.001) controlling for age and %BF. Our findings indicated that inter-limb leg LTM asymmetry negatively impacts firefighter SC performance, which may be improved with appropriate exercise interventions.

This study examined the influence of leg inter-limb lean tissue mass (LTM) asymmetry on SC performance in career firefighters. We found that inter-limb leg LTM asymmetry was associated with reduced SC performance, prior to and after controlling for age and percent body fat. Interventions that mitigate these asymmetries may improve occupational performance.

The feasibility of workload monitoring among law enforcement officers: A multi-methodological approach.

This study examined the feasibility of workload monitoring to assess internal workload in law enforcement officers (LEO) using a multi-methodological approach. Fifty front-line LEO completed workload surveys on workdays for eight weeks. Retention and adherence were assessed across the survey period. LEO completed usability and likelihood to continue questionnaires, while departmental administrators (n = 8) received workload reports and completed utility and sustainability questionnaires. A subsample of LEO and administrators participated in semi-structured interviews, following consensual qualitative research design. LEO retention (96%), survey adherence (94%), and usability scores (88.3/100) were high, with a moderate likelihood to continue to use the survey. Administration reported high utility and sustainability. The high adherence rates and usability scores, coupled with strong administrative support, suggest that workload monitoring may be a feasible strategy among LEO to monitor occupational workloads. The LEO and administration feedback highlight areas of improvement (e.g., data transparency, departmental collaboration) to inform future implementation.

Impact of Age on the Affective Responses Following Worksite Resistance Exercise in Career Firefighters.

INTRODUCTION: The purpose of this study was to examine the impact of age on the affective responses (attitude, feelings, self-efficacy, intention, enjoyment, and fondness) after a worksite circuit-style resistance exercise routine in career firefighters. METHODS: Nineteen young (25.5 ± 3.3 yr) and 19 middle-aged male career firefighters (50.3 ± 3.5 yr) completed 2 d of physical testing at local fire stations. Participants were familiarized with the resistance training exercises (deadlift, shoulder press, lunge, and upright row) at visit 1 and performed a multirepetition maximum (RM) assessment to prescribe the appropriate loads for the resistance exercise bout on visit 2. The resistance training session included three sets of 8 to 10 repetitions per exercise at 80% 1-RM. Participants completed a postexercise questionnaire examining affective responses and a rating of perceived exertion (RPE). Mann-Whitney U tests and an independent t-test were used to determine differences between the young and middle-aged firefighters' affective responses and RPE, respectively. RESULTS: There were no significant differences between groups for any of the six affective responses ( P = 0.062-0.819) or RPE ( P = 0.142). CONCLUSIONS: Age did not influence the perceived effort or affective responses following an acute bout of worksite resistance exercise. Firefighters reported overall positive attitudes, feelings, and fondness paired with high self-efficacy and intention at a training frequency of twice per week. However, confidence, intention, and enjoyment decreased at higher training frequencies (i.e., 3-4x per week). Circuit-style resistance training performed twice per week may be a feasible and practical worksite exercise routine across ages in the fire service.

The Time Course of Health, Fitness, and Occupational Performance Changes in Recruits across a Fire Academy.

PURPOSE: The purpose of this study was to examine the time course of health, fitness, and occupational performance changes in firefighter recruits across a fire academy. METHODS: Nineteen recruits (24.9 ± 4.3 yr; 26.7 ± 3.1 kg·m -2 ) had their body composition, balance, vertical jump (VJ) performance, cardiorespiratory fitness (CRF), upper and lower body strength, hamstrings-to-quadriceps (H/Q) ratio, lower back endurance, and weighted stair climb (SC) performance assessed at the beginning (week 1 [W1]), midpoint (week 15 [W15]), and end (week 30 [W30]) of a fire academy. RESULTS: The fire academy improved body composition, balance, CRF, leg extension strength, and SC performance from W1 to W15 ( P ≤ 0.042) which then plateaued at W30 ( P ≥ 0.314). Leg flexion strength and the H/Q ratio decreased from W1 to W15 ( P ≤ 0.035) and plateaued at W30 ( P ≥ 0.947). Upper body strength was similar at W1 and W15 ( P ≥ 0.999), but decreased at W30 ( P ≤ 0.033). However, no significant changes occurred across the academy for VJ performance or lower back endurance ( P ≥ 0.090). CONCLUSIONS: These findings highlight the positive effect of the academy on body composition, CRF, balance, SC performance, and leg extension strength. However, the decreases in upper body and leg flexion strength, the H/Q ratio, and lack of changes in VJ performance and low back endurance may highlight key areas of need to maximize injury prevention and performance enhancement efforts in the academy. Further, the varied time course of changes may help fire departments identify opportunities to modify exercise programming across their academies.

Test-Retest Reliability and Minimum Difference Values of a Novel and Portable Upright Row Strength Assessment in Probation Officers.

Upper body (UB) strength is important for occupational tasks and injury prevention in law enforcement officers (LEOs). Portable, reliable, and cost-effective assessments are needed to examine UB strength among LEOs in field settings. The purpose of this study was to examine the test-retest reliability and minimum difference (MD) values of a novel and portable isometric upright row assessment in probation officers. Thirty certified probation officers (18 women; age = 38.9 ± 9.0 years, body mass = 98.8 ± 27.1 kg, stature = 171.4 ± 14.0 cm) volunteered for this investigation. Testing occurred on-site across two sessions (2-5 days apart). Participants stood upon an aluminum plate with a chain attached to a handle and dynamometer. They grasped the handle with a pronated grip, two cm below the umbilicus, and performed three isometric maximal voluntary contractions. Intraclass correlation coefficient (ICC2,1), standard error of the measurement (SEM), and MD values were calculated. Results indicated no significant systematic error (p = 0.080) across sessions. The ICC2,1, SEM, and MD values for UB strength were 0.984, 27.20 N (4.1% of the mean), and 75.38 N (11.3% of the mean), respectively. These data suggest this isometric upright row assessment is a reliable, portable, and cost-effective measure of UB strength to assess and monitor LEOs in field settings.

Examining the Usability of Workload Monitoring in Firefighter Recruits.

OBJECTIVE: Although workload monitoring is commonly used in athletic settings to mitigate injury risk, we are unaware of previous studies examining its feasibility among firefighters. METHODS: Nineteen firefighter recruits completed a short online workload survey at the end of each training day (Monday-Friday) for 26 weeks during the academy. A modified System Usability Scale was provided at midtesting (3 months into the academy) and posttesting (end of the academy). RESULTS: The recruits perceived the survey to be user-friendly throughout the academy (83.6 ± 13.6). However, questions 1 (survey frequency) and 6 (survey consistency) decreased and increased from midtesting to posttesting, respectively. Adherence was overall poor, decreasing from midtesting to posttesting. CONCLUSIONS: Our findings suggest that workload monitoring is a user-friendly tool within tactical populations; however, future research should consider optimal survey frequency to enhance compliance.

Segmental bioelectrical impedance spectroscopy: A novel field assessment of muscle size and quality in normal weight and obese older men.

The purpose of this study was to determine if segmental bioelectrical impedance spectroscopy characteristic frequency (fc) and phase angle (Pa) were reflective of differences in quadriceps muscle size and quality, respectively, in normal weight and obese older men, and to assess the impact of hydration status on these measurements. Forty-one healthy older men volunteered for this study and were recruited by age (65-74 years) and two body mass index groups: normal weight and obese. Participants visited the laboratory on one occasion where they underwent a hydration status assessment via urine specific gravity, a percent body fat assessment via dual-energy X-ray absorptiometry, a segmental bioelectrical impedance spectroscopy thigh assessment to determine fc and Pa, and resting ultrasonography to assess superficial quadriceps cross-sectional area and echo intensity as a proxy for muscle quality. Urine specific gravity was not different between the groups (P = 0.116); however, echo intensity, cross-sectional area, and percent body fat were greater in the obese group (P < 0.001), and both fc and Pa were greater in the normal weight group (P < 0.001). Larger muscle cross-sectional area was associated with lower fc (r = -0.597, P < 0.001), but was not associated with Pa (P = 0.469). Poorer muscle quality (higher echo intensity) was associated with lower Pa (r = -0.765, P < 0.001), but not associated with fc (P = 0.244). There was no association between fc and Pa (P = 0.449). All group differences and associations remained unchanged after controlling for urine specific gravity. Segmental bioelectrical impedance spectroscopy may offer an inexpensive, time efficient, and portable assessment of quadriceps muscle size and quality in older men.

Neuromuscular determinants of simulated occupational performance in career firefighters.

PURPOSE: Although firefighters are required to perform various high-intensity critically essential tasks, the influence of neuromuscular function on firefighter occupational performance is unclear. The primary aim of the current study was to identify the key neuromuscular determinants of stair climb (SC) performance in firefighters. METHODS: Leg extension isometric peak torque (PT), peak power (PP), torque steadiness at 10% (Steadiness10%) and 50% (Steadiness50%) of PT, fatigability following 30 repeated isotonic concentric contractions at 40% of PT, percent body fat (%BF), and a weighted and timed SC task were examined in 41 (age: 32.3 ± 8.2 yrs; %BF: 24.1 ± 7.9%) male career firefighters. RESULTS: Faster SC times (74.7 ± 13.4 s) were associated with greater PT and PP, less fatigability, younger age, and lower %BF (r = -0.530-0.629; P ≤ 0.014), but not Steadiness10% or Steadiness50% (P ≥ 0.193). Stepwise regression analyses indicated that PP and Steadiness50% were the strongest predictors of SC time (R2 = 0.442, P < 0.001). However, when age and %BF were included in the model, these variables became the only significant predictors of SC time (R2 = 0.521, P < 0.001) due to age and %BF being collectively associated with all the neuromuscular variables (excluding Steadiness10%). CONCLUSIONS: Lower extremity neuromuscular function, specifically PP and steadiness, and %BF are important modifiable predictors of firefighter SC performance, which becomes increasingly important in aging firefighters.

The impact of repeated bouts of shiftwork on rapid strength and reaction time in career firefighters.

The purpose of this study was to examine the influence of repeated bouts of shiftwork on lower extremity maximal and rapid strength and reaction time in career firefighters. Thirty-five firefighters (3 females; 34.3 ± 9.1 years) performed a psychomotor vigilance test (PVT) and reactive maximal isometric strength assessment prior to and following a full shift rotation (three 24-hr on-off shifts). Reaction time (RT), maximal, absolute and normalised rapid strength (50, 100, 150, 200 ms), and PVT measures were assessed on-site. Separate linear regression models were used to evaluate the POST-PRE change in variables adjusted for BMI, age, sleep, and call duration. Early (50 ms) absolute rapid strength was the only variable significantly reduced (-25.9%; p = 0.031) following the full shift rotation. Our findings indicate that early rapid strength may be a sensitive measure in detecting work-related fatigue, despite minimal changes in sleep between work and non-work nights and a low call duration. Practitioner summary: We examined the impact of repeated shiftwork on changes in reaction time and neuromuscular function. Early rapid strength was a sensitive, portable lab assessment that feasibly measured work-related fatigue in career firefighters. Interventions that mitigate work-related fatigue may be impactful at preventing falls and/or risk of musculoskeletal injury.

The Influence of Sonographer Experience on Skeletal Muscle Image Acquisition and Analysis.

The amount of experience with ultrasonography may influence measurement outcomes while images are acquired or analyzed. The purpose of this study was to identify the interrater reliability of ultrasound image acquisition and image analysis between experienced and novice sonographers and image analysts, respectively. Following a brief hands-on training session (2 h), the experienced and novice sonographers and analysts independently performed image acquisition and analyses on the biceps brachii, vastus lateralis, and medial gastrocnemius in a sample of healthy participants (n = 17). Test-retest reliability statistics were computed for muscle thickness (transverse and sagittal planes), muscle cross-sectional area, echo intensity and subcutaneous adipose tissue thickness. The results show that image analysis experience generally has a greater impact on measurement outcomes than image acquisition experience. Interrater reliability for measurements of muscle size during image acquisition was generally good-excellent (ICC2,1: 0.82-0.98), but poor-moderate for echo intensity (ICC2,1: 0.43-0.77). For image analyses, interrater reliability for measurements of muscle size for the vastus lateralis and biceps brachii was poor-moderate (ICC2,1: 0.48-0.70), but excellent for echo intensity (ICC2,1: 0.90-0.98). Our findings have important implications for laboratories and clinics where members possess varying levels of ultrasound experience.

The influence of age on the recovery from worksite resistance exercise in career firefighters.

Resistance exercise is an important strategy to reduce injuries and improve performance in the fire service. However, given the large age range of firefighters, it is important to determine if age influences their recovery following an acute bout of resistance exercise. PURPOSE: To examine the changes in indirect markers of muscle damage in young and older firefighters following a feasible worksite resistance exercise routine. METHODS: Nineteen young (25.5 ± 3.4 years) and 19 older male career firefighters (50.3 ± 3.5 years) completed pre-testing, an acute bout of resistance exercise, and post-testing at 24, 48, and 72 h post-exercise at their fire station. Prior to all testing, firefighters completed a work-related fatigue (WRF) questionnaire to account for potential unanticipated differences in previous shift workloads. Testing included perceived muscle soreness, ultrasonography to quantify muscle size and echo intensity (EI) of the vastus lateralis (VL) and biceps brachii (BB), countermovement jump (CMJ) height and velocity, upper body (UB) peak force (PF), lower body (LB) PF and rapid force, and electromyographic (EMG) amplitude of the VL. The resistance training session included 3 sets of 8-10 repetitions of a deadlift, shoulder press, lunge, and upright row exercise at 80% 1-RM. All recovery variables were analyzed using a linear mixed model, controlling for WRF. RESULTS: There was no interaction (age × time) for any of the variables and a similar training volume were completed between groups (P ≥ 0.171). Muscle soreness, CMJ height and velocity, UB PF, LB rapid force and EMG amplitude at later time intervals (100-200 ms), and VL and BB muscle size were altered from baseline (P ≤ 0.044) for 48, 24, 48, 72, and 72 h post-exercise, respectively. Young firefighters exhibited greater CMJ height and velocity, LB PF, LB rapid force (200 ms), and lower VL EI values than the older firefighters (P ≤ 0.047). CONCLUSIONS: Age did not influence the recovery from an acute bout of worksite resistance exercise in firefighters. However, UB muscle strength, CMJ performance, and LB rapid force production were reduced 24-72 h post-exercise. Appropriately scheduled and chronic on-duty resistance training may mitigate these decrements.

Measuring muscle quality: associations between echo intensity and normalized strength and power.

Objective. Muscle quality has received considerable attention within the literature due to its influence on health and performance. However, it has been assessed by various measures (e.g. ultrasound imaging, normalized strength), contributing to a lack of a consensus definition. The purpose of this study was to investigate the association between common muscle quality measures: vastus lateralis echo intensity (EI) and peak torque (PT) and power (PP) normalized to thigh lean mass (TLM) and thigh fat mass (TFM).Approach. Participants' (n = 39; age = 32.7 ± 8.2 years; %BF = 24.1% ±8.1%) whole body and leg composition was assessed via dual-energy x-ray absorptiometry and custom thigh analyses. Subcutaneous fat-corrected muscle EI was assessed via ultrasonography. Maximal PT and PP of the dominant leg extensors were examined on a calibrated dynamometer and were normalized to both TLM and TFM, respectively. Pearson product-moment correlations were used to examine the associations between EI and PT/TLM, PT/TFM, PP/TLM, and PP/TFM.Main results. Greater muscle EI was significantly related with lower PT/TFM and PP/TFM (r = -0.74 to -0.70,P < 0.001), but unrelated to PT/TLM or PP/TLM (P ≥ 0.205).Significance. These findings suggest that ultrasound imaging (muscle EI) and normalized strength and power may not be used interchangeably to define muscle quality, and muscle EI may be more sensitive to the adiposity of the limb than TLM. Future research should consider using separate and consistent definitions when referring to imaging-derived or normalized strength and power values of muscle quality.

The Acute Effects of a Multi-Ingredient Herbal Supplement on Performance Fatigability: A Double-Blind, Randomized, and Placebo-Controlled Trial.

The purpose of the present study was to examine the acute effects of an herbal supplement containing a 70:30 blend of Rhaponticum carthamoides extract and Rhodiola rosea extract, respectively, on performance fatigability and the affective responses prior to and following exercise. Thirty men (age = 22.3 ± 4.1 years) volunteered for this randomized, placebo-controlled, double-blind, cross-over study. Following familiarization, participants visited the laboratory on three separate occasions where they consumed one 350 mg dose, a 175 mg dose of the supplement plus 175 mg of maltodextrin, or a placebo. Participants completed feeling, arousal, and mood surveys at supplement ingestion and following testing. Ninety minutes following ingestion, participants performed five sets of 30 maximal, concentric, leg extension muscle actions at 180°/sec, with one minute of rest between sets. Peak torque, average torque, and total work were calculated for each set, and the rating of perceived exertion (RPE) was assessed after each set. Data were analyzed with a repeated measures analysis of variance and intent-to-treat approach. For the performance variables, there was no interaction (p ≥ 0.317) or treatment effect (p ≥ 0.660), however, all torque variables decreased across sets and plateaued at sets 4-5, whereas RPE increased across sets (p < 0.001). For the affective responses, there was no interaction (p ≥ 0.781) or treatment effect (p ≥ 0.314); however, participants felt better, had an improved mood, and felt more aroused following testing (p < 0.047). This combination of herbal extracts likely does not acutely influence performance fatigability during high-intensity, repeated muscle actions.

The Influence of Age and Obesity-Altered Muscle Tissue Composition on Muscular Dimensional Changes: Impact on Strength and Function.

The purpose of this study was to determine if muscular dimensional changes with increases in torque production are influenced by age- and obesity-related increases in intramuscular fat, and its relationship to percent body fat (%BF), echo intensity (EI), strength, and maximum walking speed. Sixty-six healthy men were categorized into 3 groups based on age and body mass index status (young normal weight [YNW], older normal weight [ONW], and older obese [OB]). Participants underwent %BF assessments, resting ultrasonography to determine muscle size (cross-sectional area [CSA]) and EI of the superficial quadriceps, and a 10-m maximum walking speed assessment. Maximal and submaximal (rest-100% MVC in 10% increments) isometric leg extension strength was assessed while changes in rectus femoris (RF) CSA, width, and depth were obtained with ultrasonography. Echo intensity and %BF were different among all groups (p ≤ .007), with the YNW and OB groups exhibiting the lowest and highest %BF and EI values, respectively. The RF increased in depth and decreased in width with increases in torque intensity for all groups. The ONW group demonstrated no change (-0.08%) in RF CSA across torque intensities, whereas the YNW group (-11.5%) showed the greatest decrease in CSA, and the OB group showed a more subtle decrease (-4.6%). Among older men, a greater change in RF CSA was related to poorer EI (r = -0.355) and higher %BF (r = -0.346), while a greater decrease in RF width was associated with faster walking speeds (r = -0.431). Examining muscular dimensional changes during contraction is a unique model to investigate the influence of muscle composition on functional performance.

Influence of Demographic Characteristics and Muscle Strength on the Occupational Fatigue Exhaustion Recovery Scale in Career Firefighters.

OBJECTIVE: Little is known regarding how individual characteristics and changes in muscle strength across a shift cycle are associated with the Occupational Fatigue Exhaustion Recovery scale in career firefighters. METHODS: Thirty-two career firefighters completed lower body maximal strength testing prior to and following three 24-hour on-off shifts. Demographic data were collected prior to the first shift and the OFER15 questionnaire was completed following the last shift. RESULTS: Increased age was associated with greater acute and chronic fatigue and poorer recovery. A positive percent change in strength following a shift cycle was related to better recovery. Age was the only significant predictor of acute and chronic fatigue, while age and the change in strength were significant predictors of inter-shift recovery. CONCLUSIONS: Increased age influences all dimensions of work-related fatigue, with changes in muscle strength influencing inter-shift recovery in career firefighters.

Muscle cross-sectional area and motor unit properties of the medial gastrocnemius and vastus lateralis in normal weight and overfat children.

NEW FINDINGS: What is the central question of this study? Are differences in muscle size and motor unit properties between normal weight and overfat children muscle specific? What is the main finding and its importance? Muscle cross-sectional area and motor unit action potential amplitudes and firing rates were similar between overfat and normal weight children for both the medial gastrocnemius and vastus lateralis muscles. There was no evidence that the chronic mechanical overload provided by the greater body mass resulted in significant hypertrophy of contractile tissue or motor units that would be used during lower-to-moderate intensity activities. ABSTRACT: This study examined the possible differences in muscle cross-sectional area (mCSA), motor unit action potential amplitudes (MUAPAMPS ) and interspike intervals (ISIs) of the firing instances of the medial gastrocnemius (MG) and vastus lateralis (VL) between normal weight (NW) and overfat (OF) children aged 7-10 years. Fourteen NW (age = 8.6 ± 1.1 years, BMI = 15.8 ± 1.4 kg m-2 ) and 12 OF (age = 8.8 ± 0.9 years, BMI = 21.8 ± 2.4 kg m-2 ) children performed isometric trapezoidal muscle actions at 40% of maximal voluntary contraction of the plantar flexors and knee extensors. Surface electromyography was recorded from the MG and VL and decomposed into the firing events of motor units (MUs). Statistical procedures were performed on the composite recruitment thresholds (RTs), ISIs and MUAPAMPS of recorded MUs collapsed across subjects and the y-intercepts and slopes calculated from each subject's ISI and MUAPAMP vs. RT relationships. Ultrasound was used to assess mCSA, echo intensity (mEI), and subcutaneous fat (sFAT) of the MG and VL. The OF had greater mCSAs, mEI and sFAT (P = 0.004-0.024), but there were no differences in mCSA when accounting for mEI for the MG (P = 0.506) and VL (P = 0.326). The NW children had significantly greater composite MUAPAMPS for the VL and MG (P < 0.001), but only significantly larger MUAPAMPS of the VL remained for the NW (P < 0.001) when subjects were matched for sFAT. There were no differences between groups for the ISI or MUAPAMP vs. RT relationships (P > 0.05). These findings suggest that the OF children did not undergo significant muscle or MU hypertrophy that would be routinely activated during activities of daily living.

Age-related changes in the passive properties of the plantarflexors: Influence of tissue size and quality.

BACKGROUND: Limited research exists examining the influence of age on the passive mechanical properties of the muscle-tendon unit. The purpose of the present study was to 1) investigate the age-related differences in maximum range of motion (MRoM), stretch tolerance (maximal tolerable torque), and the dissipation coefficient (DC), and 2) examine the influence of plantarflexor muscle size and quality on the age-related differences in the DC. METHODS: Twenty-one young and 14 older men completed a MRoM assessment to determine peak torque (PTpass), energy stored (area under the loading curve), energy restituted (area under the unloading curve), and the DC (normalized hysteresis) from the angle-torque curve. Ultrasonography was used to determine muscle cross-sectional area (CSA) and subcutaneous fat corrected echo intensity (EI) of the gastrocnemii. FINDINGS: The PTpass, MRoM, and energy restituted were greater (P ≤ 0.046) in the young men, whereas the DC and EI were greater (P ≤ 0.024) in the older men. When accounting for CSA, differences between groups for the DC remained (P = 0.028), while there were no longer differences between groups when accounting for EI (P = 0.120). PTpass was also strongly related to MRoM (r = 0.755, P < 0.001). INTERPRETATION: Older men exhibited lower dorsiflexion MRoM and a greater DC, which may be explained by an altered stretch tolerance and qualitative changes (i.e., non-contractile tissue infiltration) in aged skeletal muscle leading to greater energy dissipated, respectively.

Obesity Prevalence and Musculoskeletal Injury History in Probation Officers.

PURPOSE: The purpose of the present investigation was to identify 1) the prevalence of overweight and obesity and 2) factors associated with previous work-related musculoskeletal injury, and physical activity (PA) levels in North Carolina probation officers. METHODS: North Carolina probation officers (N = 1866) were sent a questionnaire on demographics, work history, injury history, and PA. A multivariable logistic regression model estimated the odds of reporting work-related musculoskeletal injury history within the past year, and multivariable ordinal logistic regression estimated the odds of reporting lower PA levels in the previous month. Odds ratios (OR) with 95% confidence intervals (CI) excluding 1.00 were deemed significant. RESULTS: Complete data were available for 1323 probation officers (70.9% completion rate; 46.5% female; mean ± SD age, 39.9 ± 10.0 yr). Officers that were classified as overweight and obese were 80.8% (body mass index [BMI] ≥ 25 kg·m), with 49.9% and 9.5% categorized as obese (BMI ≥ 30 kg·m) and severely obese (BMI ≥ 40 kg·m), respectively. Being older (1-yr increase; OR, 1.06; 95% CI, 1.04-1.09) and severely obese (compared to normally weighted; OR, 2.56; 95% CI, 1.19-5.51) was associated with a greater odds of sustaining a work-related musculoskeletal injury in the past year. A higher number of years of employment (1-yr increase; OR, 1.03; 95% CI, 1.01-1.04), being overweight or obese (compared to normal weight; OR, 1.57-3.22) and being female (compared with male: OR, 0.38; 95% CI, 0.31-0.47) was associated with the greater odds of lower PA levels in the previous month. CONCLUSIONS: The prevalence of obesity is alarmingly high in probation officers, and is associated with a greater likelihood of sustaining previous work-related musculoskeletal injury and engaging in lower amounts of PA. Public safety administrators may consider worksite exercise/diet interventions and annual physical employment standards to combat obesity.

Relationships Between Neuromuscular Function and Functional Balance Performance in Firefighters.

The purpose of the present study was to examine the relationships between neuromuscular function and functional balance performance in firefighters. Fifty career firefighters (35.1 ± 7.5 yr) performed isometric leg extension and flexion muscle actions to examine peak torque (PT), and absolute (aTQ) and normalized (nTQ; %PT) rapid torque variables at 50, 100, 150, and 200 ms. A performance index (PI) was determined from the functional balance assessment completion time. Partial correlations were used to examine the relationship between the PI and the maximal and rapid TQ variables for each muscle and the composite value, while controlling for demographic data related to the PI. Multiple regression analyses examined the relative contributions of the maximal and rapid aTQ variables, and demographic data on the PI. After controlling for age and %BF, the majority of the later aTQ and nTQ variables (100-200 ms) and PT were associated with the PI (r = -0.501--0.315). Age, %BF, and aTQ100 explained 42-50% of the variance in the PI. Lower rapid strength, increased age, and poorer body composition were related to worse performance during the functional balance assessment. Strategies to improve rapid strength and %BF, especially in aging firefighters may impact dynamic balance abilities in firefighters.