Force and Neuromuscular Responses During a Handgrip Hold to Failure Anchored to a Moderate Perceptual Intensity in Males.

OBJECTIVES: The current study investigated performance fatigability (PF) and time course of changes in force, electromyographic amplitude (EMG AMP) and frequency (EMG MPF), and neuromuscular efficiency (NME) during a sustained, isometric, handgrip hold to failure (HTF) using the rating of perceived exertion (RPE)-Clamp Model. METHODS: Twelve males performed a handgrip HTF anchored to RPE=5. The time to task failure (Tlim), force (N), EMG AMP and MPF, and NME (normalized force/ normalized EMG AMP) were recorded. Analyses included a paired samples t-test for PF at an alpha of p<0.05, 1-way repeated measures ANOVA across time and post-hoc t-tests (p<0.0025) for force, EMG AMP and MPF, and NME responses. RESULTS: The PF (pre- to post- maximal force % decline) was 38.2±11.5%. There were decreases in responses, relative to 0% Tlim, from 40% to 100% Tlim (force), at 30%, 60%, and 100% Tlim (EMG AMP), from 10% to 100% Tlim(EMP MPF), and from 50% to 65%, and 80% to 100% Tlim (NME) (p<0.0025). CONCLUSIONS: The RPE-Clamp Model in this study demonstrated that pacing strategies may be influenced by the integration of anticipatory, feedforward, and feedback mechanisms, and provided insights into the relationship between neuromuscular and perceptual responses, and actual force generating capacity.

The Influence of Emergency Call Volume on Occupational Workload and Sleep Quality in Urban Firefighters.

OBJECTIVE: To determine the impact of emergency call volume on exertion, autonomic activity, and sleep among urban structural firefighters. METHODS: Thirty-four firefighters wore a wrist-based monitor to track sleep and autonomic parameters and rated their level of perceived exertion (RPE) and subjective sleepiness after a 24-hour shift. Predictive variables included total run time and total run time after 11:59 PM. RESULTS: Total run time and sleep duration accounted for RPE and subjective sleepiness; while total run time and total run time after 11:59 PM accounted for sleep durations on-duty. CONCLUSIONS: The current results suggest emergency call volume is associated with indicators of exertion and sleep. As such, call volume tracking is an important consideration for departments to ensure personnel readiness and wellness and provide a method of tracking the occupational demands experienced by firefighters on-duty.

Firefighter Health: A Narrative Review of Occupational Threats and Countermeasures.

Structural firefighters are responsible for protecting properties and saving lives during emergency operations. Despite efforts to prepare firefighters for these hazardous occupational demands, the unfortunate reality is that the incidence of health morbidities is increasing within the fire service. Specifically, cardiovascular disease, cancer, and mental health disorders are among the most documented morbidities in firefighters. Pubmed and Google Scholar search engines were used to identify peer-reviewed English language manuscripts that evaluated firefighters' occupational health threats, allostatic factors associated with their occurrence, and evidence-based strategies to mitigate their impact. This narrative review provides fire departments, practitioners, and researchers with evidence-based practices to enhance firefighters' health.

Etiology of Exercise Injuries in Firefighters: A Healthcare Practitioners' Perspective.

The purpose of this study was to query healthcare practitioners (HCPs) who treat firefighter injuries to identify risk factors and mechanisms associated with musculoskeletal injuries during exercise. A phenomenological design was utilized to understand the experiences of HCPs while treating firefighters' musculoskeletal injuries due to exercise. Semi-structured interviews were conducted with 14 HCPs. Two interviews were pilot-tested with HCPs to ensure reliability and validity. Interviews were transcribed and uploaded to a qualitative analysis software program. Although the study inquired about injuries incurred by any exercise modality (e.g., endurance and resistance training), injuries induced during resistance training were prominent among HCPs as resistance training emerged as a primary exercise injury mechanism. HCPs indicated that the back and shoulder were prevalent anatomical exercise injury locations. Risk factors for exercise injuries included age, immobility, movement proficiency, and factors associated with fatigue. Exercise injury mechanisms included poor resistance training technique and overexertion. These findings could guide exercise program design, use of movement assessments, and the identification of other countermeasures to decrease the risk of resistance training exercise injuries among firefighters.

Evaluation of Work Efficiency in Structural Firefighters.

ABSTRACT: Langford, EL, Bergstrom, HC, Lanham, S, Eastman, AQ, Best, S, Ma, X, Mason, MR, and Abel, MG. Evaluation of work efficiency in structural firefighters. J Strength Cond Res 37(12): 2457-2466, 2023-To perform occupational tasks safely and effectively, firefighters (FF) must work quickly and consume air provided by the self-contained breathing apparatus (SCBA) efficiently. However, most literature only factors work rate into performance, neglecting the inherent time limitation imposed by the SCBA. The purpose of this article was to (a) evaluate the reliability and variability in a "work efficiency" (WE) performance metric reflective of both work rate and air consumption; (b) explore the relationship between WE and established measures of metabolic strain; and (c) identify fitness, anthropometric, and demographic correlates of WE. About 79 structural FF completed an air consumption drill while breathing through an SCBA. Self-paced work duration and air consumption were entered into the WE equation. A subsample of FF (n = 44) completed another randomized trial while breathing through a portable gas analyzer. Anthropometric and fitness data were collected separately. Correlations were performed between WE vs. fitness, anthropometric, demographic, and metabolic outcomes. Multiple linear regression was used to identify the strongest predictors of WE. WE was reliable (intraclass correlation coefficient = 0.71) and yielded inter-FF variability {0.79 ± 0.25 ([lb·in-2·min]-1) × 104; coefficient of variation = 31.6%}. WE was positively correlated to oxygen consumption (V̇O2) (L·minute-1, mL·kg-1·minute-1) and tidal volume and negatively correlated to V̇E/V̇O2 and respiratory frequency. Height, upper-body endurance, and aerobic endurance were identified as the strongest predictors of WE (adjusted R2 = 0.59, RMSE = 0.16). WE is a reliable and occupationally relevant method to assess FF performance because it accounts for work rate and air consumption. Firefighters may enhance WE through a training intervention focused on improving metabolic tolerance, upper-body endurance, and aerobic endurance.

Responses to Exercise at the Critical Heart Rate vs. the Power Output Associated With the Critical Heart Rate.

ABSTRACT: Succi, PJ, Dinyer-McNeely, TK, Voskuil, CC, Abel, MG, Clasey, JL, and Bergstrom, HC. Responses to exercise at the critical heart rate vs. the power output associated with the critical heart rate. J Strength Cond Res 37(12): 2362-2372, 2023-This study examined the physiological (volume of oxygen consumption [V̇ o2 ], heart rate [HR], power output [PO], respiration rate [RR], muscle oxygen saturation [%SmO 2 ]), neuromuscular (electromyographic and mechanomyographic amplitude [EMG AMP and MMG AMP] and mean power frequency [EMG MPF and MMG MPF]), and perceptual (rating of perceived exertion [RPE]) responses during exercise anchored at the critical heart rate (CHR) vs. the PO associated with CHR (PCHR). Nine subjects (mean ± SD ; age = 26 ± 3 years) performed a graded exercise test and 4 constant PO trials to exhaustion at 85-100% of peak PO (PP) to derive CHR and PCHR on a cycle ergometer. Responses were recorded during trials at CHR (173 ± 9 b·min -1 , time to exhaustion [T Lim ] = 45.5 ± 20.2 minutes) and PCHR (198 ± 58 W, T Lim = 21.0 ± 17.8 minutes) and normalized to their respective values at PP in 10% intervals. There were significant ( p ≤ 0.05) mode (CHR vs. PCHR) × time (10%-100% T Lim ) interactions for all variables ( p < 0.001-0.036) except MMG AMP ( p > 0.05). Post hoc analyses indicated differences across time for CHR V̇ o2 (%change = -22 ± 16%), PCHR V̇ o2 (19 ± 5%), CHR RR (24 ± 23%), PCHR RR (45 ± 14%), CHR PO (-33 ± 11%), PCHR HR (22 ± 5%), CHR RPE (22 ± 14%), PCHR RPE (39 ± 6%), CHR %SmO 2 (41 ± 33%), PCHR %SmO 2 (-18 ± 40%), CHR EMG AMP (-13 ± 15%), PCHR EMG AMP (13 ± 13%), CHR EMG MPF (9 ± 8%), CHR MMG MPF (7 ± 11%), and PCHR MMG MPF (-3 ± 14%). The critical heart rate was more sustainable than PCHR but required adjustments in PO which traversed intensity domains and caused dissociations of the responses previously observed in exercise anchored to PO. These dissociations indicated the demands to exercise varied with anchoring scheme and provides an important consideration for practitioners prescribing endurance exercise.

Comparison of Acute Arterial Responses Following a Rescue Simulation and Maximal Exercise in Professional Firefighters.

Cardiovascular events are the leading cause of on-duty deaths among firefighters. Screening firefighters for risk of sudden cardiac event is a critical element of a comprehensive medical program. Although intense physical exertion has been shown to trigger sudden cardiac events in the general population, it is unclear how hemodynamic responses following clinical exercise testing compare to that of performing firefighting tasks in personal protective equipment. Therefore, the purpose of this study was to compare hemodynamic responses following rescue simulation (RS) and maximal exercise in firefighters. This was a cross-over repeated measures study. Thirty-eight professional firefighters (31.8 ± 5.2 yr; VO2peak: 57.9 mL/kg/min) completed a maximal aerobic exercise test (MAET) and an RS. Pulse wave velocity (PWV), pulse pressure (PP), and brachial and central mean arterial pressure (MAP) were measured before and 5 and 15 min post-exercise. The findings indicated that femoral PWV decreased after MAET and RS at both time points (p < 0.005). No significant differences were found in aortic and carotid PWV over time or between conditions (p ≥ 0.05). Significant increases in brachial and central PP and MAP were noted 5 min post-MAET and RS (p = 0.004). In conclusion, the present study demonstrated that peripheral arterial stiffness (AS) decreased in firefighters following both conditions, with no differences in central AS. Our findings provide valuable information on hemodynamic responses similar between RS and MAET, and are important for controlling CVD risk and the AS response.

The Acute Effect of High-Intensity Resistance Training on Subsequent Firefighter Performance.

ABSTRACT: Mason, MR, Heebner, NR, Abt, JP, Bergstrom, HC, Shapiro, R, Langford, EL, and Abel, MG. The acute effect of high-intensity resistance training on subsequent firefighter performance. J Strength Cond Res 37(7): 1507-1514, 2023-High-intensity resistance training (HIRT) is commonly performed by structural firefighters on duty to enhance occupational readiness. However, exercise-induced fatigue may negatively impact subsequent occupational performance. Therefore, the purpose of this study was to assess the acute effect of HIRT on subsequent occupational physical ability in structural firefighters and to determine the time course of recovery. Seven resistance-trained male firefighters performed a timed maximal effort simulated fireground test (SFGT) in 3 randomized conditions: baseline (SFGT baseline ), 10 minutes post HIRT (SFGT 10min ), and 60 minutes post HIRT (SFGT 60min ). Work efficiency and air depletion were assessed during the SFGT. The timed HIRT session consisted of a standardized set of exercises using absolute training loads. Repeated measures analysis of variance and minimal difference (MD) analysis assessed group and individual effects between the conditions, respectively. The level of significance was set at p < 0.05. SFGT 10min completion time was greater than SFGT baseline (430 ± 137 vs. 297 ± 69 seconds, p < 0.01), with no difference between SFGT baseline and SFGT 60min (297 ± 69 vs. 326 ± 89 seconds, p = 0.08). The MD analysis indicated that all firefighters' SFGT 10min times exceeded the MD (±26.4 seconds) compared with SFGT baseline . However, 43% of firefighters still exceeded the MD at SFGT 60min . Air depletion during SFGT 10min was greater than that during SFGT baseline (2,786 ± 488 vs. 2,186 ± 276 lb·in -2 , p = 0.02), with no difference between SFGT baseline and SFGT 60min ( p = 0.25). Work efficiency during SFGT 10min was 40% lower than that during SFGT baseline ( p < 0.01), with no difference between SFGT baseline and SFGT 60min ( p = 0.25). These findings indicate that an acute bout of HIRT decreases multiple descriptors of firefighters' occupational performance 10 minutes post exercise with varied responses at 60 minutes post exercise.

The Impact of Gloves and Occupational Tasks on Handgrip Strength in Structural Firefighters.

Adequate handgrip strength (HGS) is important to safely perform fireground tasks. However, there is limited research describing the deleterious impact of glove use and fatigue from occupational tasks on HGS. Therefore, the aims of this investigation were to quantify the impact of glove use and occupational tasks on HGS, to explore the relationship between HGS versus the glove and task-induced decrement in HGS, and to evaluate the relationship between HGS and decrement in HGS versus occupational performance. Fourteen (Male: n = 13) career structural firefighters (Age: 35.5 ± 7.2 yr) performed a maximal isometric HGS assessment with and without gloves before and immediately following completion of a simulated fireground test (SFGT). General linear model with written contrast was used to identify significant differences in HGS between conditions. Pearson Correlations were used to describe bivariate relationships between the decrements in HGS and occupational task times. Significance was set at p < 0.05. There were significant main effects indicating that gloves, performing occupational tasks, and their combined effects decreased HGS (p < 0.001 for all). There were strong inverse relationships between baseline (barehanded) HGS versus the decrement in HGS from donning gloves (r = -0.82, p < 0.001) and from performing occupational tasks with gloves (r = -0.61, p = 0.021). Baseline HGS and the decrement in HGS due to wearing gloves and performing occupational tasks were not correlated to the timed completion of occupational tasks (p ≥ 0.27). These findings suggest that the use of regulation fire gloves and work-induced fatigue reduces HGS and these decrements are related to HGS. Practitioners are encouraged to utilize training strategies to optimize HGS among structural firefighters.

Implementation of High Intensity Interval Training and Autoregulatory Progressive Resistance Exercise in a Law Enforcement Training Academy.

The purpose of this investigation was to assess the feasibility and efficacy of implementing autoregulatory progressive resistance exercise (APRE) and high intensity interval training (HIIT) methodologies to improve physical fitness and occupational physical ability in police cadets. Two law enforcement academy classes were stratified into a standard care academy training cohort (SC; n=32, m=27, f=5) and a high performance cohort (HP; n=31; m=27, f=4) that utilized APRE and HIIT methodologies during a 17-week academy training program. Demographic, internal loading parameters, anthropometric, fitness outcomes (i.e., 1.5-mile run, 1-repetition maximum bench press, sit-up repetitions, push-up repetitions, & 300m run) and timed completion of a occupation physical ability test (OPAT) were collected at three academy time points (entrance, mid-point and exit). Mixed factor (time vs. group) repeated measures ANOVA were used to evaluate the effects of the training intervention on performance outcomes. Significance was set at p<0.05. Both groups demonstrated significant improvements in all fitness outcomes except the OPAT from entrance to exit tests (p<0.05). The HP experienced greater improvements in push-up performance compared to the SC (p<0.001). OPAT time decreased in both groups from entrance to midpoint, but significantly increased from baseline to exit (p<.05). Despite similar inter-group fitness improvements, the HP reported lower session RPE values (p<0.01), indicating fitness adaptations occurred at a lower internal load. This study demonstrated the feasibility of successfully implementing APRE and HIIT methodologies within a cadet population. Furthermore, these methodologies produced similar improvements in cadet fitness and occupational performance at a lower internal load.

Unilateral Handgrip Holds to Failure Result in Sex-Dependent Contralateral Facilitation.

This study examined changes in maximal voluntary isometric contraction (MVIC) force following dominant (Dm) and nondominant (NDm) unilateral, handgrip isometric holds to failure (HTF) for the exercised ipsilateral (IPS) and non-exercised contralateral (CON) limbs and determined if there are sex- and hand- (Dm vs NDm) dependent responses in the HTF time, performance fatigability (PF) for the exercised IPS limb, and changes in MVIC force for the CON limb after unilateral fatigue. Ten men and 10 women (Age = 22.2 years) completed an isometric HTF at 50% MVIC for the Dm and NDm hand on separate days. Prior to, and immediately after the HTF, an MVIC was performed on the IPS and CON limbs, in a randomized order. The Dm (130.3 ± 36.8 s) HTF (collapsed across sex) was significantly longer (p = 0.002) than the NDm (112.1 ± 34.3 s). The men (collapsed across hand) demonstrated IPS (%Δ = 22.9 ± 10.8%) PF and CON facilitation (%Δ = -6.1 ± 6.9%) following the HTF, while the women demonstrated differences in PF between the Dm and NDm hands for the IPS (%Δ Dm = 28.0 ± 9.4%; NDm = 32.3% ± 10.1%; p = 0.027), but not the CON limb (%Δ Dm = -1.6 ± 5.7%; NDm = 1.7 ± 5.9%). The cross-over facilitation of the CON limb for men, but not women, following a unilateral, isometric handgrip HTF may be related to post-activation potentiation.

Quadriceps electromyography during flywheel-based inertial training (FIT) and dynamic constant external resistance (DCER) squats at similar tempo.

Flywheel-based iso-inertial training (FIT) has been purported to provide enhanced adaptations to muscle overload compared to dynamic constant external resistance (DCER), but previous studies have not controlled for exercise intensity. We compared quadriceps electromyography (EMG) amplitude between FIT- and DCER-squats with similar tempo. Eleven (5 M and 6F) resistance-trained participants completed sets of five maximal velocity FIT (0.025 kg∙m2) and DCER (55 ± 15 %1RM) squats. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were measured. Repetition time and peak knee angles were similar between FIT and DCER squats. Mean knee angular velocity during the concentric (122.2 ± 23.6 vs. 108.9 ± 22.9, p = 0.022, Cohen's D: 0.820), but not eccentric, phase was significantly greater during FIT. Peak VM (210.4 ± 49.3 vs. 177.5 ± 56.3 %MVIC, p = 0.001; Cohen's D: 1.416), but not VL or RF, EMG amplitude was significantly greater in FIT compared to DCER. Mean EMG amplitude was significantly (p < 0.001) greater during the concentric than the eccentric phase for the VL and VM but not RF. Mean EMG amplitude was not significantly different between modes during either the concentric or eccentric phase. Quadriceps EMG amplitude is largely similar between FIT and DCER squats when matched for movement velocity.

The Effect of Tactical Tasks and Gear on Muscle Activation of SWAT Officers.

ABSTRACT: Keeler, JM, Pohl, MB, Bergstrom, HC, Thomas, JM, and Abel, MG. The effect of tactical tasks and gear on muscle activation of SWAT officers. J Strength Cond Res 36(1): 238-244, 2022-Special Weapons and Tactics (SWAT) officers perform a variety of tactical operations while wearing tactical gear. Load carriage has been shown to alter muscle activation in the torso and is also associated with lower back pain, which is a prevalent musculoskeletal injury suffered by SWAT Officers. The purpose of this study was to quantify the effect of tactical gear on muscle activation of torso musculature while performing occupational tasks. Twenty male SWAT Officers (age: 34.7 ± 4.5 years; height: 1.79 ± 0.1 m; body mass: 91.5 ± 17.3 kg) performed 4 tasks (standing, rifle walk, sitting, and shield walk) with and without gear (mass of gear: 13.8 ± 1.9 kg). Mean electromyographic amplitude was evaluated bilaterally for the erector spinae, rectus abdominis, and external oblique muscles during the trials and expressed relative to maximal voluntary isometric contraction (MVIC). Addition of gear significantly increased erector spinae mean muscle activation during the rifle walk task (mean delta: +0.16%). However, no differences in muscle activation were identified for any other muscles between gear conditions (effect size ≤ 0.15). The shield walk produced the highest mean activation for each muscle during different tasks. The dynamic tasks yielded (0.24-4.18% MVIC) greater muscle activation levels than sitting and standing tasks. Despite minimal increases in muscle activation levels with the addition of gear, load carriage is known to increase the risk of acute and chronic injury. Collectively, these findings indicate that SWAT Officers should perform most skills without gear during tactical training to simulate task-specific movement patterns but reduce the risk of musculoskeletal injury.

Predictors of Arterial Stiffness in Law Enforcement Officers.

BACKGROUND: Compare arterial stiffness among law enforcement officers (LEOs) versus general population normative values and identify predictors of arterial stiffness in LEOs. METHODS: Seventy male LEOs (age: 24-54 years) completed body composition, blood pressures, physical activity level, and carotid-femoral pulse wave velocity (cfPWV) measurements. T-tests and regression analyses were utilized to compare LEO data to normative data and predict cfPWV, respectively. RESULTS: Compared to similar age strata within the general population, cfPWV was lower among LEO's under 30-years (mean difference = -0.6 m·s-1), but higher among LEOs 50-55-years (mean difference = 1.1 m·s-1). Utilizing regression, age, relative body fat, and diastolic blood pressure explained the greatest variance in LEO's cfPWV (adj. R2 = 0.56, p < 0.001). CONCLUSION: This investigation demonstrated that arterial stiffness may progress more rapidly in LEOs and LEOs' relative body fat and blood pressure may primarily affect arterial stiffness and risk of CVD.

Predictors of Work Efficiency in Structural Firefighters.

OBJECTIVE: Develop a novel work efficiency (WE) metric to quantify firefighter physical ability and identify correlates of WE. METHODS: Physical fitness and anthropometric measurements were taken on 19 male firefighters. Firefighters performed a timed maximal effort simulated fireground test (SFGT). WE was quantified as: (1/[Air depletion × SFGT completion time]) × 10,000. Regression analyses were used to identify predictors of WE. RESULTS: WE was significantly correlated to age, relative body fat, fat mass, occupational experience, jump height, inverted row repetitions, relative bench press and squat strength, treadmill time to exhaustion, relative ventilatory threshold, and relative peak oxygen consumption. Treadmill time to exhaustion and relative lower body strength accounted for the greatest variance in WE (R2 = 0.72, root mean square error = 0.07). CONCLUSION: Aerobic endurance and relative lower body strength were related to an occupationally-specific assessment of firefighter physical ability.

Impact of Time Restricted Feeding on Fitness Variables in Professional Resistance Trained Firefighters.

Firefighters are at an elevated risk for cardiometabolic disease and sudden cardiac death due to physiological and psychological stressors. Research suggests time restricted feeding (TRF) may improve health and performance variables. OBJECTIVE: This study investigated the effects of a 7-week TRF (14-hour fasting:10-hour eating window) on fitness variables related to physical health and performance among professional, resistance-trained firefighters. METHODS: Several fitness variables were assessed pre- and post-TRF intervention. RESULTS: Relative and absolute ventilatory threshold (VT) increased (P < 0.05), relative and absolute , decreased (P < 0.05), and muscular strength, endurance, and power were not affected pre- versus post-intervention. CONCLUSION: Although , decreased, all other performance variables were not negatively impacted by TRF. Improvements in VT may be associated with improvements to markers of endurance exercise performance in firefighters, but more data are needed to confirm this hypothesis.

Effect of a Law Enforcement Academy Training Program on Validated Fitness Outcomes of Cadets.

ABSTRACT: Martinez, GJ and Abel, MG. Effect of a law enforcement academy training program on validated fitness outcomes of cadets. J Strength Cond Res 35(4): 955-962, 2021-The purpose of this investigation was to assess the efficacy of a law enforcement training program on physical fitness outcomes in police cadets. A convenience sample of 138 male and 8 female police cadets participated in a 23-week law enforcement training academy with validated fitness assessments conducted at entrance, midpoint, and exit from the academy. Demographic, anthropometric, and fitness data (i.e., 1.5-mile run, 1 repetition maximum bench press, sit-up repetitions, push-up repetitions, and 300-m run) were retrospectively collected. Analysis of variance was used to identify the influence of training on fitness outcomes over time and between cadet subgroup stratifications. Statistical significance for this study was set at p ≤ 0.05. All cadet subgroups (specialty-stratified and sex-stratified cohorts) exceeded the validated fitness standards on academy entrance and exit (p ≤ 0.01). The entire cohort significantly improved all fitness outcomes throughout the training program. Furthermore, improvements in all fitness outcomes were significantly greater from entrance to midpoint (4.4-35.7%, p ≤ 0.001) vs. midpoint to exit (1.2-15.4%, p < 0.05). Specifically, there were greater relative improvements in push-ups and sit-ups (57.5 and 28.7%, respectively; p < 0.001) compared with bench press (13.8%, p < 0.001), 300-m run (5.8%, p < 0.001), and 1.5-mile run (12.1%, p < 0.001). Regarding female cadets, the average relative improvement in fitness outcomes from entrance to exit assessments was superior compared to male counterparts for all fitness tests except sit-ups. Moreover, the specialty cadets produced lower 1.5-mile run times than nonspecialty cadets throughout the academy. Overall, the academy improved occupationally relevant fitness outcomes, with greater improvements occurring earlier in the academy.

Methodological Considerations for the Determination of the Critical Load for the Deadlift.

ABSTRACT: Moss, AC, Dinyer, TK, Abel, MG, and Bergstrom, HC. Methodological considerations for the determination of the critical load for the deadlift. J Strength Cond Res 35(2S): S31-S37, 2021-This study determined whether performance method during conventional deadlifting affects critical load (CL) estimates derived from the linear work limit (Wlim) vs. repetitions relationship. Eleven subjects completed 1-repetition maximum (1RM) deadlift testing followed by separate visits, to determine the number of repetitions to failure at 50, 60, 70, and 80% 1RM for both reset (RS) and touch-and-go (TG) methods. The CL was the slope of the line of total work completed (load [kg] × repetitions) vs. total repetitions for 4 intensities (50-80% 1RM). The number of repetitions to failure were determined at CLRS and CLTG. The kg values and repetitions to failure at CLRS and CLTG, and total repetitions at each intensity (50-80%) for each method (RS and TG) were compared. There were no significant mean differences (±SD) in kg values (-0.4 ± 7.9 kg, range = -8.8 to 17 kg, p = 0.856), %1RM (-1.2 ± 5.6%, p = 0.510), or total repetitions completed (2.8 ± 15.7 reps, range = -15 to 37 reps, p = 0.565) for CLRS and CLTG. These findings indicated that performance method did not affect mean estimation of CL or number of repetitions completed at submaximal loads. Thus, the estimates of CL from the modeling of total work vs. repetitions were relatively robust to variations in deadlifting methodologies. However, individual variability (range of scores) in kg values and repetition to failure at CLRS and CLTG indicated that deadlifting methods may differ in anatomical region of fatigue. The CL is an individually derived threshold that may be used to examine and describe performance capabilities.

Construct Validity, Test-Retest Reliability, and Repeatability of Performance Variables Using a Flywheel Resistance Training Device.

Bollinger, LM, Brantley, JT, Tarlton, JK, Baker, PA, Seay, RF, and Abel, MG. Construct validity, test-retest reliability, and repeatability of performance variables using a flywheel resistance training device. J Strength Cond Res 34(11): 3149-3156, 2020-Power production is highly associated with physical performance; however, the ability to quantitatively measure power output during resistance exercise is lacking. The purpose of this study was to determine the validity and test-retest reliability of flywheel-based performance testing. Twelve young, resistance trained subjects completed 2 bouts of resistance exercise using a flywheel resistance training device (Exxentric kbox 4 Pro). Each session consisted of 3 sets of 3 exercise (bent-over row, Romanian deadlift, and biceps curl) with varying moments of inertia (0.050, 0.075, and 0.100 kg·m, respectively) in random order. Each set consisted of 5 maximal effort repetitions with 3-minute recovery between sets. Average power, peak concentric and eccentric power, average force, average speed, and total work for each set were recorded. Regression analysis revealed a near-perfect relationship between measured and predicted power, force, and work at given workloads. Pearson's r between trials 1 and 2 revealed good (≥0.70) to excellent (≥0.90) test-retest reliability for all outcomes with the exception of peak eccentric power for biceps curls (r = 0.69), which narrowly missed the cutoff for acceptable reliability. Bland-Altman plots revealed small (approximately 5-15%), but statistically significant bias between the 2 trials for some measures. Coefficient of repeatability for all outcomes was relatively high, indicating poor repeatability. Flywheel-based performance testing provides valid data. However, reliability varies between individual lifts and specific outcomes. Given the poor repeatability between trials, it is likely that subjects who are unaccustomed to this modality may require multiple testing sessions or a thorough familiarization period to ensure accurate measures of power, force, speed, and work during flywheel-based performance testing.

Effects of Curcumin and Fenugreek Soluble Fiber on the Physical Working Capacity at the Fatigue Threshold, Peak Oxygen Consumption, and Time to Exhaustion.

Herrick, LP, Goh, J, Menke, W, Campbell, MS, Fleenor, BS, Abel, MG, and Bergstrom, HC. Effects of curcumin and fenugreek soluble fiber on the physical working capacity at the fatigue threshold, peak oxygen consumption, and time to exhaustion. J Strength Cond Res 34(12): 3346-3355, 2020-The purpose of this study was to examine the effects of curcumin in combination with fenugreek soluble fiber (CUR + FEN) or fenugreek soluble fiber alone (FEN) on the neuromuscular fatigue threshold (PWCFT), peak oxygen consumption (V˙o2peak), and time to exhaustion (Tlim) on a graded exercise test (GXT), in untrained subjects. The PWCFT estimates the highest power output that can be maintained without evidence of neuromuscular fatigue. Forty-seven untrained, college-aged subjects were randomly assigned to one of 3 supplementation groups; placebo (PLA, n = 15), CUR + FEN (500 mg·d, n = 18), or FEN (300 mg·d, n = 14). The subjects completed a maximal GXT on a cycle ergometer to determine the PWCFT, V˙o2peak, and Tlim before (PRE) and after (POST) 28 days of daily supplementation. Surface electromyographic signals were recorded from a bipolar electrode arrangement on the vastus lateralis of the right leg during each test. Separate one-way analysis of covariances were used to determine if there were between-group differences for adjusted POST-PWCFT, POST-V˙o2peak, and POST-Tlim values, covaried for the respective PRE-test scores. The adjusted POST-PWCFT for the CUR + FEN group (mean ± SD: 196 ± 58 W) was greater (p = 0.016) than the PLA group (168 ± 49 W) but the FEN group (185 ± 32 W) was not different from the CUR + FEN or PLA groups (p > 0.05). There were no differences for adjusted POST-V˙o2peak (p = 0.612) or POST-Tlim (p = 0.508) among the groups. These findings suggested curcumin combined with fenugreek soluble fiber might delay neuromuscular fatigue.