Karl Friedl | US Army (original) (raw)

Papers by Karl Friedl

BMJ Nutrition, Prevention & Health, Oct 27, 2023

Women's roles in the US military have progressively changed over the past several decades. Previo... more Women's roles in the US military have progressively changed over the past several decades. Previously women were barred from combat roles. Recent change in policy allow women into combat roles in the Marine Corps, and this has led to women being trained for combat specialties. Objectives This observational cross-sectional study describes body composition and performance values for modern Marine Corps women. Methods Volunteers were 736 Marine women who were assessed for body composition and physical performance; (age 29.5±7.3 (18-56) years; height 163.6±6.8 (131.0-186.1) cm; body mass 68.3±9.2 (42.0-105.3) kg; years in the military 8.9±6.8 (0.5-37) years-in-service). Body composition measures were obtained using dual-energy X-ray absorptiometry and single-frequency bioelectrical impedance analyses. Performance measures were obtained from official physical and combat fitness test scores (PFT; CFT) as well as from data on measured countermovement jumps (CMJ) on a calibrated force platform. Results Mean body composition metrics for Marine women were: 47.5±5.7 fat free mass (FFM) (kg), 30.1%±6.4% body fat (%BF), 2.6±0.3 bone mineral content (kg), and 25.5±2.8 body mass index (kg/m 2); performance metrics included 43.4±3.2 maximal oxygen uptake (VO2max; mL. kg. min), 22.4±7.1 CMJ height (cm) and 2575±565.2 CMJ peak power (W). Data showed strong correlations (r) (≥0.70) between PFT and VO2max scores (0.75), and moderate correlations (≥0.50) between CFT and VO2max scores (0.57), CFT and PFT scores (0.60), FFM and CMJ peak power (W) (0.68), and %BF to VO2max (−0.52), PFT (−0.54), CMJ-Ht (−0.52) and CMJ relative power (W/kg) (−0.54). Conclusion Modern Marine women are both lean and physically high performing. Body composition is a poor predictor of general physical performance. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY ⇒ Study establishes 'ideal' body fat for healthy active women. ⇒ These values cannot be simply extrapolated from men.

BMJ Military Health, 2020

Journal of Science and Medicine in Sport, 2018

Objective: In the British Army, fitness is assessed by a load carriage test (Annual Fitness Test,... more Objective: In the British Army, fitness is assessed by a load carriage test (Annual Fitness Test, AFT) and by a three event Personal Fitness Assessment (PFA). Body composition based on body mass index (BMI) and abdominal circumference (AC) is also part of a mandatory annual assessment. This study examined the influence of BMI and AC on fitness test results within a comprehensive sample of British Army personnel. Design: Secondary analyse were carried out on data obtained from the 2011 Defence Analytical Services and Advice (DASA) database for 50,635 soldiers (47,173 men and 3,462 women). Methods: Comparisons using loglinear analysis were made between groups of individuals classified by body mass index as obese (≥30 kg/m2) and not obese (<30 kg/m2), and further classified using combined BMI and AC for obesity-related health risks to compare "no risk" with "increased risk." Results: Not obese or "no risk" soldiers had a significant relationship with success in the AFT (p < 0.01) and PFA (p < 0.01). Of those soldiers who attempted the AFT, 99% of men and 92% of women passed; for the PFA, 92% of men and 91% of women passed. Obese or "at risk" soldiers were more likely to fail and far less likely to take both tests (p < 0.05). Compared to older obese soldiers, young obese soldiers were more likely to attempt the tests. Conclusions: We conclude that BMI and AC are useful indicators of fitness test outcome in the British Army.

Military Medicine, 1997

Each of the military services classifies individuals in their weight control programs using perce... more Each of the military services classifies individuals in their weight control programs using percent body fat predicted by circumference-based equations. Although derived independently from service-specific samples, each of the male. equations relies on waist circumference adjusted by a neck circumference. In this study, the authors examined the performance of the equations in 496 young «40 years) male soldiers, compared to percent body fat measured by dual-energy X-ray absorptiometry. The strength of the relati~nship.to~ercent bo~y fat improved from body mass index (weight/height), to a Waist circumference alone, to the difference between waist and neck circumferences. Overweight men who were misclassified by overestimation of total percent body fat using the equations (2.6% of the total sample) had normal neck circumferences and height but large waistlines, indicating that they were still classified appropriately to the goals of the weight control programs, all of which center on abdominal adiposity. The authors demonstrate that each of the service equations yield substantially similar results and discuss why a single equation could be easily agreed to and used by the Department of Defense for male body fat prediction.

Military Medicine, 2017

Background: Many people are unaware of the science underlying the biophysical properties of Soldi... more Background: Many people are unaware of the science underlying the biophysical properties of Soldier clothing and personal protective equipment, yet there is a well-refined biomedical methodology initiated by Army physiologists in World War II. This involves a methodical progression of systematic material testing technologies, computer modeling, and human testing that enables more efficient development and rapid evaluation of new concepts for Soldier health and performance. Sophisticated manikins that sweat and move are a central part of this testing continuum. This report briefly summarizes the evolution and use of one specialized form of the manikin technologies, the thermal hand model, and its use in research on Soldier hand-wear items that sustain dexterity and protect the hand in extreme environments. Methods: Thermal manikin testing methodologies were developed to provide an efficient and consistent analytical tool for the rapid evaluation of new clothing concepts. These methods have been upgraded since the original World War II and Korean War eras to include articulation and sweating capabilities, as characterized and illustrated in this article. The earlier "retired" versions of thermal hand models have now been transferred to the National Museum of Health and Science. Findings: The biophysical values from manikin testing are critical inputs to the U.S. Army Research Institute of Environmental Medicine mathematical models that provide predictions of soldier comfort, duration of exposure before loss of manual dexterity, and time to significant risk of freezing (skin temperature <−1°C) and nonfreezing cold injuries (skin temperature <5°C). The greater thickness of better insulated handwear reduces dexterity and also increases surface area which makes added insulation increasingly less effective in retaining heat. Measurements of both thermal resistance (insulation) and evaporative resistance (permeability) collectively characterize the biophysical properties and enable mathematical modeling of the human thermophysiological responses. This information can help guide the hand-wear development and selection process which often requires trade-offs between factors such as material, cost, and sizing. Impact: Soldier hands provide fine motor dexterity in tactical functions, ranging from pulling a trigger to pulling a parachute ripcord; thus, protecting hand function is critical to soldier readiness. Also, the importance of protection against nonbattle cold injuries was highlighted during World War II in northern Europe, in the Aleutian Islands, and later in Korea. The U.S. Army has been on the forefront of the biophysical analysis of clothing including gloves since environmental research was established at the Armored Medical

This report summarizes the research findings that led to the policy decisions for development of ... more This report summarizes the research findings that led to the policy decisions for development of the body fat content screening procedures and equations that are currently under consideration for inclusion in the Department of Defense (DoD) Instruction (DoDI) 1308.3, Physical Fitness and Body Fat Programs. At a DoD meeting on 21 May 1998, results of a review by the Committee on Body Composition, Nutrition and Health, Military Nutrition Committee, Institute of Medicine were presented. It was recommended that a tiered body fat content standard be adopted. A weightfor-height screen would be adopted based on the recommendations of the Healthy People 2000 Committee: Healthy weights are represented by body mass index (BMI) values between 19 and 25, irrespective of gender. Service members exceeding the weight-for-height standards would have their body fat content determined. Men with body fat content values less than 20% body weight and women with values less than 30% body weight would be considered within standards. Men with values greater than 20% fat, but less than or equal to 26% fat, would be in a "cautionary zone" and acceptability of their body fat content would depend on performance on the Service's physical fitness test. For women, the cautionary zone values would be 30 to 36% fat.

American Journal of Clinical Nutrition

ABSTRACT

Biobehavioral Resilience to Stress, 2008

Journal of Diabetes Science and Technology, 2007

BMJ Military Health

BackgroundThe creation of highly muscled and strong fighters is a recurring theme in human perfor... more BackgroundThe creation of highly muscled and strong fighters is a recurring theme in human performance enhancement concepts. Physical readiness standards, intended to prevent obesity in the military, produce contradictory objectives, hounding large individuals to lose weight because of confusion between body size and body composition. Through selection, specialised training and policy exceptions the US Marine Corps has successfully developed a unique group of large (body mass index (BMI) >30 kg/m2) and strong individuals, the body bearers (BB) who carry coffins of Marines to their final resting place.MethodsWe examined the relationship between adiposity and body size from nine male BB (age 25.0±2.1, height: 1.84±0.04 (1.80–1.92) m, BMI: 33.0±2.1 (30–37) kg/m2). Body composition was assessed by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance (BIA) and tape measured abdominal circumference (AC)-based equations and from three-dimensional scanning (3DS).ResultsMeasure...

Physiological Measurement, 2021

Objectives.To investigate the validity of different devices and algorithms used in military organ... more Objectives.To investigate the validity of different devices and algorithms used in military organizations worldwide to assess physical activity energy expenditure (PAEE) and heart rate (HR) among soldiers. Design. Device validation study. Methods. Twenty-three male participants serving their mandatory military service accomplished, firstly, nine different military specific activities indoors, and secondly, a normal military routine outdoors. Participants wore simultaneously an ActiHeart, Everion, MetaMax 3B, Garmin Fenix 3, Hidalgo EQ02, and PADIS 2.0 system. The PAEE and HR data of each system were compared to the criterion measures MetaMax 3B and Hidalgo EQ02, respectively. Results. Overall, the recorded systematic errors in PAEE estimation ranged from 0.1 (±1.8) kcal.min−1 to −1.7 (±1.8) kcal.min−1 for the systems PADIS 2.0 and Hidalgo EQ02 running the Royal Dutch Army algorithm, respectively, and in the HR assessment ranged from −0.1 (±2.1) b.min−1 to 0.8 (±3.0) b.min−1 for the ...

IEEE Open Journal of Engineering in Medicine and Biology, 2020

Journal for the Measurement of Physical Behaviour, 2018

ECTemp™ is a heart rate (HR)-based core temperature (CT) estimation algorithm mainly used as a re... more ECTemp™ is a heart rate (HR)-based core temperature (CT) estimation algorithm mainly used as a real-time thermal-work strain indicator in military populations. ECTemp™ may also be valuable for resting CT estimation, which is critical for circadian rhythm research. This investigation developed and incorporated a sigmoid equation into ECTemp™ to better estimate resting CT. HR and CT data were collected over two calorimeter test trials from 16 volunteers (age, 23 ± 3 yrs; height, 1.72 ± 0.07 m; body mass, 68.5 ± 8.1 kg) during periods of sleep and inactivity. Half of the test trials were combined with ECTemp™’s original development dataset to train the new sigmoid model while the other was used for model validation. Models were compared by their estimation accuracy and precision. While both models produced accurate CT estimates, the sigmoid model had a smaller bias (−0.04 ± 0.26°C vs. −0.19 ± 0.29°C) and root mean square error (RMSE; 0.26°C vs. 0.35°C). ECTemp™ is a validated HR-based ...

Temperature, 2019

Physiological responses to work in cold water have been well studied but little is known about th... more Physiological responses to work in cold water have been well studied but little is known about the effects of exercise in warm water; an overlooked but critical issue for certain military, scientific, recreational, and professional diving operations. This investigation examined core temperature responses to fatiguing, fully-immersed exercise in extremely warm waters. Twenty-one male U.S. Navy divers (body mass, 87.3 ± 12.3 kg) were monitored during rest and fatiguing exercise while fully-immersed in four different water temperatures (Tw): 34.4, 35.8, 37.2, and 38.6°C (Tw 34.4 , Tw 35.8 , Tw 37.2 , and Tw 38.6 respectively). Participants exercised on an underwater cycle ergometer until volitional fatigue or core temperature limits were reached. Core body temperature and heart rate were monitored continuously. Trial performance time decreased significantly as water temperature increased (Tw 34.4 , 174 ± 12 min; Tw 35.8 , 115 ± 13 min; Tw 37.2 , 50 ± 13 min; Tw 38.6 , 34 ± 14 min). Peak core body temperature during work was significantly lower in Tw 34.4 water (38.31 ± 0.49°C) than in warmer temperatures (Tw 35.8 , 38.60 ± 0.55°C; Tw 37.2 , 38.82 ± 0.76°C; Tw 38.6 , 38.97 ± 0.65°C). Core body temperature rate of change increased significantly with warmer water temperature (Tw 34.4 , 0.39 ± 0.28°C•h −1 ; Tw 35.8 , 0.80 ± 0.19°C•h −1 ; Tw 37.2 , 2.02 ± 0.31°C•h −1 ; Tw 38.6 , 3.54 ± 0.41°C•h −1). Physically active divers risk severe hyperthermia in warmer waters. Increases in water temperature drastically increase the rate of core body temperature rise during work in warm water. New predictive models for core temperature based on workload and duration of warm water exposure are needed to ensure warm water diving safety.

BMJ Nutrition, Prevention & Health

Bioelectrical impedance analysis (BIA) provides a practical method of body composition estimation... more Bioelectrical impedance analysis (BIA) provides a practical method of body composition estimation for field research and weight management programmes, with devices and algorithms that have improved in recent years. We compared suitability of a commercial BIA system that uses multi-frequency-based proprietary algorithms (InBody 770, Cerritos, California, USA) and a laboratory-based validated single-frequency system (Quantum IV, RJL Systems, Clinton Township, Michigan, USA) with dual-energy X-ray absorptiometry (DXA) (iDXA, GE Lunar, Madison, Wisconsin, USA). Volunteers included fit non-obese active duty US Marines (480 men; 315 women), assessed by DXA and the two BIA systems. Both RJL and InBody BIA devices predicted DXA-based fat-free mass (FFM) (mean absolute error (MAE) 2.8 and 3.1 kg, respectively) and per cent body fat (%BF) (MAE 3.4% and 3.9%, respectively), with higher correlations from the InBody device (r2=0.96 (%BF) and 0.84 (FFM)) versus the RJL (r2=0.92 (%BF) and 0.72 (FF...

BMJ Nutr Prev Med, 2023