Body Mass Bias and Occupational Relevance of Military Physical Fitness Tests Paul M. Vanderburgh, EdD Professor & Chair Department of Health and Sport Science University of Dayton, Dayton, Ohio

BLUF The Evidence Suggests: Military Physical Fitness Tests 1.Are not potent indicators of performance of typical, loaded military tasks 2.Impose a systematic bias against larger, not fatter, service members 3.1. and 2. are interrelated Solutions 1.Scaled Values 2.Correction Factors 3.Balanced Fitness Tests (validation needed)

Military Physical Fitness

How Fitness is Assessed (Army, Air Force, Navy) Sit-ups or Curl-ups Push-upsDistance Run

Military Physical Fitness Tests Conducive to mass testing No special equipment needed Body weight is the primary resistance

Typical Physically Demanding Military Tasks Light Load Carriage Heavy Load Carriage Heavy Handling

Light Load Carriage

Heavy Load Carriage

Heavy Handling

Occupational Relevance

Free Carry and Stretcher Carry Performance Strongest correlates of free carry and stretcher carry performance: –High LBM to dead mass (FM + plus casualty mass) ratio –Standing broad jump –Upright pull (Bilzon Occup Med ‘02)

Load Carriage Determinants Time to exhaustion on 18kg Load Carriage (LC) test was: –Not correlated with relative VO 2max –Positively correlated with LBM Simplified aerobic physical fitness tests (e.g., 2.4 km run) did not predict ability to perform LC tasks (Bilzon Occup Med ‘01)

Absolute VO 2max and LBM/DM were the most potent predictors of %VO 2max during heavy (40 kg) LC tasks Absolute VO 2max, LBM/DM, gradient, and load accounted for 89% of variance in %VO 2max (Lyons Occup Med ’05) Load Carriage Determinants

PF Tests as Predictors of Military Performance Body size, muscle strength, and aerobic fitness (L/min) differentially predicted lifting and load carriage task performance –Not push-ups –Sit-ups generally weak –Relative VO 2max only for light load carriage (Rayson Ergonomics ‘00)

PU, SU, 2MR Military Task Performance, 18 kg loaded 30m sprint to and from prone position –Vertical jump and 2MR 400M sprint –2MR and vertical jump Obstacle course –Long jump, SU, vertical jump Casualty recovery –Body mass, vertical jump, and 2MR (Harman MSSE (abstract) 2007)

Occupational Relevance and Physical Fitness Tests Conclusions Military physical fitness test performance is generally not a potent predictor of loaded task performance LBM, LBM/DM, upright pull, 1RM lift, and absolute VO 2max are more predictive of load carriage performance

Body Mass Bias

Body Mass Bias 101 Defined as the non-zero correlation between body mass and a physical performance measure –Push-ups, sit-ups –Distance run –1RM strength Free of the confounding effects of effort, body fat, or physical activity level Theoretical basis

Example – 5K Run data from Crecelius MSSE ’07 (abstract)

Comparison of Runners B is 8.5% slower than A A B

Comparison considering body mass Distance from the best-fit curve B is 8.6% faster than A A B

Body Mass Bias Example Powerlifting TOTAL (data from IPF website: 5/07)

TOTAL per M Ratio Method

TOT per M 2/3

Scale Modeling of Body Mass Bias A 25% increase in mass (exact replica): 1RM bench press is 16.0% greater VO 2max (L/min) is 16.0% greater Run Time is 7.7% slower Push-ups and Sit-ups Reps are 7.2% fewer

Body Mass (M) and Strength Theory Strength α muscle CSA Muscle CSA α M 2/3 Therefore strength α M 2/3 Fair comparison: 1RM/M 2/3 (Astrand & Rodahl, Textbook of Work Physiology ’86)

M Bias and Strength Evidence MeasureSubjectsNExponentsSource Powerlifting Elite Women Elite Women 36 world record holders 36 world record holders Vanderburgh MSSE ‘00 Powerlifting Elite Men 30 world record holders 0.49 – 0.68 Dooman JSCR ‘00 Olympic Lifting Elite M & W * Batterham, JAP ‘97 Bench Press M college-age PE students Markovic EJAP ‘04 Leg Strength Young M & W Jaric JSMPF ‘02 Exponents are somewhat variable Not all confidence intervals contain 0.67 but none contain 1.0 or 0 *Found simple allometric model problematic

Body Mass and VO 2max Theory VO 2max (L) α M Time α M 1/3 VO 2max (L/min) α M/M 1/3 Therefore VO 2max (L/min) α M 2/3 Fair index: ml O 2 /(kg 2/3. min) (Astrand & Rodahl Textbook of Work Physiology ’86)

Body Mass and VO 2max Evidence SubjectsN M Exponent Source Young W (LBM exp = 1.04) Vanderburgh MSSE ‘96 M, yr 1, * (LBM exp = 0.97) Batterham, JAP ‘99 Young fit M & W Nevill EJAP ‘92 M & W, yr ** Heil MSSE ‘97 *Found the simple allometric model problematic **Controlling for age, gender, %fat and SR-PA score

Body Mass and Distance Run Time (RT) Theory 5K run speed (RS) α VO 2max (ml/kg. min) But VO 2max (L/min) α M 2/3 So RS α M 2/3 /M or RS α M/ -1/3 Given that RT α RS -1 RT α M 1/3 Fair index: RT/M 1/3 (Nevill JAP ’92, Vanderburgh MPEES ‘07)

Body Mass and Distance Run Time (RT) Evidence MeasureSubjectsNExponentsSource 2-mile RT M USMA cadets (FFW exp. = 0.31) Vanderburgh JSCR ‘95 2-mile RT M USMA cadets (LBM exp = 0.24) Crowder MSSE (abstract ’96) 5K Run Young fit M & W * Nevill EJAP ‘92 5K Run 5K M Runners ** Crecelius JSCR ’08 Exponents not diff. from 0.33 but diff. from 0 *Indirectly calculated from: run speed = f(VO 2max, body mass) equation **calculated using subjects with RPE > 16

Body Mass and Push-ups/Sit-ups REPS Theory Muscle force α M 2/3 REPS α M 2/3 /M or M -1/3 Push-up, Sit-up REPS α M -1/3 Fair index: REPS. M 1/3 (Markovic EJAP ‘04)

Body Mass and Push-ups/Sit-ups REPS Evidence MeasureSubjectsNExponentsSource Push-ups M USMA cadets (LBM exp = -0.28) Crowder MSSE (abstract ’96) Sit-ups M USMA cadets (LBM exp = -0.24)* Crowder MSSE (abstract ’96) Push-ups M college-age PE students Markovic EJAP ’04 Push-ups M college-age PE students Markovic EJAP ’04 Only exponent diff. from and only slightly No studies on women

Run Time, Effort and %Fat Age & Wt 5K Handicap Model –Penalty for fat > credit for extra weight (Vanderburgh MPEES ’07) –With RT/M 1/3, small remaining bias is accounted for by RPE and % fat (Crecelius JSCR ’08)

Body Mass Bias Conclusions for Military Physical Fitness Tests Military physical fitness test events favor lighter individuals, independent of body fatness Distance Run –RT α M 1/3 –Fair index = RT/T 1/3 Push-up, Sit-ups –REPS α M -1/3 –Fair index = REPS. M 1/3

Implications/Solutions

Body Mass Bias Penalty - Navy (Vanderburgh, Mil Med, 2006)

Body Mass Bias and Occupational Relevance Connection The more potent predictors of loaded military task performance (LBM, LBM/DM, upright pull, 1RM lift, and absolute VO 2max ) tend to favor heavier individuals (LBM, LBM/DM, upright pull, 1RM lift, and absolute VO 2max ) Empirical and theoretical evidence suggests that common physical fitness test events favor lighter individuals Middle ground?

Occupational Relevance and Body Mass Bias BW Resistance Only Fixed W Resistance Only Heavy equipment or supplies lifting/carriage Light load carriage over distance Heavy load carriage over distance P’ups, S’ups, Distance Runs Most physical military tasks Fitness tests

Backpack Run Test (Vanderburgh Mil Med ’00) 59 USMA male cadets –Lean, fit –Two-mile run times Modeled effects of alterations in backpack weight (BW) via ACSM equations on two-mile run times Backpack weights of kg: –No body mass bias –Reflected load carriage weights expected of combat support and/or combat arms service members Eliminating bias may be congruent with occupational relevance

Solution 1: Scaled Values Requires calculator Creates strange currency SubjectPush-ups Body Mass REPS. M 1/3 A67 80 kg B70 68 kg 281.7

Solution 2: Correction Factors Correction Factor (CF) : a dimensionless number multiplied by raw score –Based on body mass –Uses weight standard (e.g., 50 kg) Example: woman, 172 lbs, 16:08 RT –CF = (125/172) 1/3 = 0.90 –RTadj = 14:31 (Vanderburgh Mil Med ’07)

Correction Factors Push-ups and Sit-ups (Vanderburgh Mil Med ‘07)

Correction Factors – Effect (Vanderburgh Mil Med ‘07)

Solution 3: Balanced Tests Balance of body mass bias via events. Example: –1RM Bench press –Distance run time Logistics challenges Has not been empirically evaluated

2005 Pump and Run 5K run time minus (30 x Bench Press Reps) = adjusted score Bench Press weight a % of BW and age-adjusted Despite intent, imposes a substantial body mass bias Proposal: correction factors or everyone lifts the same absolute weight (Vanderburgh JSCR 2008)

Conclusions Current physical fitness tests of the Army, Navy, and Air Force: –Are not potent determinants of physical military task performance –Impose a physiological bias against heavier service members Eliminating body mass bias may be more occupationally relevant – must be tested empirically Solutions –Scaled values require no change to fitness test protocol but create strange currency –Correction factors provide ease of calculation, preservation of original units, and require no equipment –Balanced fitness tests require equipment but no calculations – need validation

References 1. Astrand PO, Rodahl K. Textbook of Work Physiology. New York, NY: McGraw Hill, Batterham AM, George KP: Allometric modeling does not determine a dimensionless power function ratio for maximal muscular function. J Appl Physiol 1997; 83: Batterham AM, Vanderburgh PM, Mahar MT, Jackson AS. Modeling the influence of body size on VO2peak: Effects of model choice and body composition. J Appl Physiol 1999; 87: Bilzon JL, Scarpello EG, Bilzon E, Allsop J. Generic task-related occupational requirements for Royal Navy personnel. Occup Med 2002; 52: Bilzon JL, Allsopp AJ, Tipton MJ. Assessment of physical fitness for occupations encompassing load-carriage tasks. Occup Med 2001; 51: Crecelius A, Vanderburgh PM, Laubach LL. Contributions of body composition and effort in the 5K run age and body weight handicap model. J Strength Cond Res 2008;22: Crowder T,. Yunker C: Scaling of push-up, sit-up and two-mile run performances by body weight and fat-free weight in young, fit men. [Abstract.]. Med Sci Sports Exercise 1996; 28: S Dooman CS, Vanderburgh PM. Allometric modeling of the bench press and squate: Who is the strongest regardless of body mass? Journal of Strength and Conditioning Research 2000; 14: Harman EA, Frykman PN, Gutekunst DJ, Nindl BC. Med Sci Sports Exerc 2007 (abstract); 39: S Heil DP. Body mass scaling of peak oxygen uptake in 20- to 79-yr-old adults. Med Sci Sport Exerc 1997; 29: Jaric S, Ugarkovic D, Kukolj M. Evaluation of methods of normalizing muscle strength in elite and young athletes. J Sports Med Phys Fit 2002; 42: Lyons J, Allsopp A, Bilzon J. Influences of body composition upon the relative metabolic and cardiovascular demands of load-carriage. Occup Med 2005; 55:

References 13. Markovic G, Jaric S. Movement performance and body size: The relationship for different groups of tests. Eur J Appl Physiol 2004; 92: Nevill AM, Ramsbottom R, Williams C. Scaling physiological measurements for individuals of different body size. Eur J Appl Physiol 1992; 65: Rayson MP, Holliman D, Belyavin A. Development of physical selection procedures for the British Army. Phase 2: Relationship between physical performance tasks and criterion standards. Ergonomics 2000; 43: U.S. Air Force Instruction Fitness Program. January 2004; pp U.S. Army Field Manual Physical Fitness Training. October 1998; pp – U.S. Navy OPSNAVINST G. Physical Readiness Test (PRT). October 2002; p Vanderburgh PM, Mahar MT. Scaling of 2-mile run times by body weight and fat-free weight in college-age men. J Strength Cond Res 1995; 9: Vanderburgh PM, Katch FI: Ratio scaling of VO2max penalizes women with larger percent body fat, not lean body mass. Med Sci Sport Exercise 1996; 28: Vanderburgh PM, Dooman C: Considering body mass differences, who are the world’s strongest women? Med Sci Sports Exercise 2000; 32: Vanderburgh PM, Flanagan S. The Backpack Run Test: A model for a fair and occupationally relevant military fitness test. Mil Med 2000; 165: Vanderburgh PM, Crowder TA. Body weight penalties in the physical fitness tests of the Army, Air Force, and Navy. Mil Med 2006; 171: Vanderburgh PM. Correction factors for body mass bias in military physical fitness tests. Mil Med 2007; in press. 25. Vanderburgh PM, Laubach LL. Derivation of an age and weight handicap for the 5K run. Meas Phys Ed Exerc Sci 2007; 11: Vanderburgh PM, Laubach LL. Body mass bias in a competition of muscle strength and aerobic power. J Strength Cond Res 2008;22: