Body Mass Bias and Body Mass Bias and Occupational Relevance of Occupational Relevance of

Military Physical Fitness TestsMilitary Physical Fitness Tests

Paul M. Vanderburgh, EdDPaul M. Vanderburgh, EdDProfessor & ChairProfessor & Chair

Department of Health and Sport ScienceDepartment of Health and Sport Science

University of Dayton, Dayton, OhioUniversity of Dayton, Dayton, Ohio

BLUFBLUFThe Evidence Suggests:The Evidence Suggests:

Military Physical Fitness TestsMilitary Physical Fitness Tests1.1. Are not potent indicators of performance of Are not potent indicators of performance of

typical, loaded military taskstypical, loaded military tasks

2.2. Impose a systematic bias against larger, not Impose a systematic bias against larger, not fatter, service membersfatter, service members

3.3. 1. and 2. are interrelated1. and 2. are interrelated

Solutions Solutions 1.1. Scaled ValuesScaled Values

2.2. Correction Factors Correction Factors

3.3. Balanced Fitness Tests (validation needed)Balanced Fitness Tests (validation needed)

Military Physical FitnessMilitary Physical Fitness

How Fitness is Assessed How Fitness is Assessed (Army, Air Force, Navy)(Army, Air Force, Navy)

Sit-ups or Curl-ups

Push-ups Distance Run

Military Physical Fitness TestsMilitary Physical Fitness Tests Upper Body

Muscular Strength/Endurance

Trunk Muscular Strength/Endurance

Aerobic Capacity

Army 2 min Push-ups 2 min Sit-ups 2 Mile Run Air Force 1 min Push-ups 1 min Sit-ups 1.5 Mile Run Navy 2 min Push-ups 2 min Curl-ups 1.5 Mile Run

• Conducive to mass testing

• No special equipment needed

• Body weight is the primary resistance

Typical Physically Demanding Typical Physically Demanding Military TasksMilitary Tasks

Light Load CarriageLight Load Carriage

Heavy Load CarriageHeavy Load Carriage

Heavy HandlingHeavy Handling

Light Load CarriageLight Load Carriage

Heavy Load CarriageHeavy Load Carriage

Heavy HandlingHeavy Handling

Occupational RelevanceOccupational Relevance

Free Carry and Stretcher Carry Free Carry and Stretcher Carry PerformancePerformance

Strongest correlates of Strongest correlates of free carryfree carry and and stretcher carrystretcher carry performance: performance: – High LBM to dead mass (FM + plus casualty High LBM to dead mass (FM + plus casualty

mass) ratiomass) ratio– Standing broad jump Standing broad jump – Upright pullUpright pull

(Bilzon (Bilzon Occup MedOccup Med ‘02) ‘02)

Load Carriage DeterminantsLoad Carriage Determinants

Time to exhaustion on 18kg Load Carriage Time to exhaustion on 18kg Load Carriage (LC) test was:(LC) test was:– Not correlated with relative VONot correlated with relative VO2max2max

– Positively correlated with LBMPositively correlated with LBM

Simplified aerobic physical fitness tests Simplified aerobic physical fitness tests (e.g., 2.4 km run) did not predict ability to (e.g., 2.4 km run) did not predict ability to perform LC tasksperform LC tasks

(Bilzon (Bilzon Occup MedOccup Med ‘01) ‘01)

Absolute VOAbsolute VO2max2max and LBM/DM were the most and LBM/DM were the most

potent predictors of %VOpotent predictors of %VO2max2max during heavy (40 during heavy (40

kg) LC taskskg) LC tasks

Absolute VOAbsolute VO2max2max, LBM/DM, gradient, and load , LBM/DM, gradient, and load

accounted for 89% of variance in %VOaccounted for 89% of variance in %VO2max2max

(Lyons (Lyons Occup MedOccup Med ’05) ’05)

Load Carriage DeterminantsLoad Carriage Determinants

PF Tests as Predictors of Military PF Tests as Predictors of Military PerformancePerformance

Body size, muscle strength, and aerobic Body size, muscle strength, and aerobic fitness (L/min) differentially predicted lifting fitness (L/min) differentially predicted lifting and load carriage task performanceand load carriage task performance– Not push-upsNot push-ups– Sit-ups generally weakSit-ups generally weak

– Relative VORelative VO2max2max only for light load carriage only for light load carriage

(Rayson Ergonomics ‘00)

PU, SU, 2MR Military Task PU, SU, 2MR Military Task Performance, 18 kg loadedPerformance, 18 kg loaded

30m sprint to and from prone position30m sprint to and from prone position– Vertical jump and 2MRVertical jump and 2MR

400M sprint400M sprint– 2MR and vertical jump2MR and vertical jump

Obstacle courseObstacle course– Long jump, SU, vertical jumpLong jump, SU, vertical jump

Casualty recoveryCasualty recovery– Body mass, vertical jump, and 2MRBody mass, vertical jump, and 2MR

(Harman (Harman MSSEMSSE (abstract) 2007) (abstract) 2007)

Occupational Relevance and Occupational Relevance and Physical Fitness Tests ConclusionsPhysical Fitness Tests Conclusions

Military physical fitness test performance is Military physical fitness test performance is generally not a potent predictor of loaded task generally not a potent predictor of loaded task performanceperformance

LBM, LBM/DM, upright pull, 1RM lift, and LBM, LBM/DM, upright pull, 1RM lift, and absolute VOabsolute VO2max2max are more predictive of load are more predictive of load

carriage performancecarriage performance

Body Mass BiasBody Mass Bias

Body Mass Bias 101Body Mass Bias 101

Defined as the non-zero correlation Defined as the non-zero correlation between body mass and a physical between body mass and a physical performance measureperformance measure– Push-ups, sit-upsPush-ups, sit-ups– Distance runDistance run– 1RM strength1RM strength

Free of the confounding effects of effort, Free of the confounding effects of effort, body fat, or physical activity levelbody fat, or physical activity levelTheoretical basisTheoretical basis

Example – 5K RunExample – 5K Run

600

1100

1600

100.0 150.0 200.0 250.0

Body Weight (lbs)

5K

Ru

n T

ime

(s

ec

)

data from Crecelius MSSE ’07 (abstract)data from Crecelius MSSE ’07 (abstract)

Comparison of RunnersComparison of Runners

600

1100

1600

100.0 150.0 200.0 250.0

Body Weight (lbs)

5K

Ru

n T

ime

(s

ec

)

B is 8.5% slower than A

AB

Comparison considering body mass Comparison considering body mass Distance from the best-fit curveDistance from the best-fit curve

600

1100

1600

100.0 150.0 200.0 250.0

Body Weight (lbs)

5K

Ru

n T

ime

(s

ec

)

B is 8.6% faster than A

AB

Body Mass Bias ExampleBody Mass Bias ExamplePowerlifting TOTALPowerlifting TOTAL

(data from IPF website: www.powerlifting-ipf.com, 5/07)

500

600

700

800

900

1000

1100

40 60 80 100 120 140

Body Mass (kg)

To

tal W

t L

ifte

d (

SQ

+B

P+

DL

, in

kg

)

TOTAL per MTOTAL per MRatio MethodRatio Method

7

8

9

10

11

12

13

40 60 80 100 120 140

Body Mass (kg)

To

tal L

ifte

d /

Bo

dy

Ma

ss

TOT per MTOT per M2/32/3

30

35

40

45

50

55

40 60 80 100 120 140

Body Mass (kg)

TO

T/M

^2/

3

Scale Modeling of Body Mass BiasScale Modeling of Body Mass Bias

A 25% increase in mass (exact replica):• 1RM bench press is 16.0% greater

• VO2max (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 StrengthBody Mass (M) and StrengthTheoryTheory

Strength Strength αα muscle CSA muscle CSA

Muscle CSA Muscle CSA αα M M2/32/3

Therefore strength Therefore strength αα MM2/32/3

Fair comparison: Fair comparison: 1RM/M1RM/M2/32/3

(Astrand & Rodahl, Textbook of Work Physiology ’86)

M Bias and StrengthM Bias and StrengthEvidenceEvidence

MeasureMeasure SubjectsSubjects NN ExponentsExponents SourceSource

PowerliftingPowerlifting Elite WomenElite Women 36 world 36 world record holdersrecord holders

0.63 - 0.87 Vanderburgh Vanderburgh MSSEMSSE ‘00 ‘00

PowerliftingPowerlifting Elite MenElite Men 30 world 30 world record holdersrecord holders

0.49 – 0.68 Dooman Dooman JSCRJSCR ‘00 ‘00

Olympic Olympic LiftingLifting Elite M & WElite M & W 5757 0.47* Batterham, Batterham,

JAPJAP ‘97 ‘97

Bench PressBench Press M college-age M college-age PE studentsPE students 7777 0.69 Markovic Markovic

EJAPEJAP ‘04 ‘04

Leg StrengthLeg Strength Young M & WYoung M & W 401401 0.67 Jaric Jaric JSMPFJSMPF ‘02‘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 VOBody Mass and VO2max2max TheoryTheory

VOVO2max2max (L) (L) αα M M

Time Time αα M M1/31/3

VOVO2max2max (L/min) (L/min) αα M/M M/M1/31/3

Therefore VOTherefore VO2max2max (L/min) (L/min) αα MM2/32/3

Fair index: Fair index: ml Oml O22/(kg/(kg2/3.2/3.min)min)

(Astrand & Rodahl Textbook of Work Physiology ’86)

Body Mass and VOBody Mass and VO2max2max EvidenceEvidence

SubjectsSubjects NN M ExponentM Exponent SourceSource

Young WYoung W 94940.61 (LBM exp =

1.04)Vanderburgh Vanderburgh

MSSEMSSE ‘96 ‘96

M, 17-66 yrM, 17-66 yr 1,3141,3140.65* (LBM exp =

0.97)Batterham, Batterham, JAPJAP

‘99‘99

Young fit M & WYoung fit M & W 308308 0.67 Nevill Nevill EJAPEJAP ‘92 ‘92

M & W, 20-79 yrM & W, 20-79 yr 440440 0.65** Heil Heil MSSEMSSE ‘97 ‘97

*Found the simple allometric model problematic

**Controlling for age, gender, %fat and SR-PA score

Body Mass and Distance Run Time (RT) Body Mass and Distance Run Time (RT)

TheoryTheory

5K run speed (RS) 5K run speed (RS) αα VO VO2max2max (ml/kg (ml/kg..min)min)

But VOBut VO2max2max (L/min) (L/min) αα M M2/32/3

So RS So RS αα M M2/32/3/M or RS /M or RS αα M/ M/-1/3-1/3

Given that RT Given that RT αα RS RS-1-1

RT RT αα MM1/31/3

Fair index: Fair index: RT/MRT/M1/31/3

(Nevill JAP ’92, Vanderburgh MPEES ‘07)

Body Mass and Distance Run Time (RT) Body Mass and Distance Run Time (RT) EvidenceEvidence

MeasureMeasure SubjectsSubjects NN ExponentsExponents SourceSource

2-mile RT2-mile RT M USMA M USMA cadetscadets 5959

0.40 (FFW exp. = 0.31)

Vanderburgh Vanderburgh JSCRJSCR ‘95‘95

2-mile RT2-mile RT M USMA M USMA cadetscadets 238238

0.26 (LBM exp = 0.24)

Crowder Crowder MSSEMSSE (abstract ’96)(abstract ’96)

5K Run5K Run Young fit M & Young fit M & WW

308308 0.33* Nevill Nevill EJAPEJAP ‘92 ‘92

5K Run5K Run 5K M Runners5K M Runners 5656 0.30** Crecelius JSCR ’08Crecelius JSCR ’08

• Exponents not diff. from 0.33 but diff. from 0

• *Indirectly calculated from: run speed = f(VO2max, body mass) equation

• **calculated using subjects with RPE > 16

Body Mass and Push-ups/Sit-ups REPSBody Mass and Push-ups/Sit-ups REPSTheoryTheory

Muscle force Muscle force αα M M2/32/3

REPS REPS αα M M2/32/3/M or M/M or M-1/3-1/3

Push-up, Sit-up REPS Push-up, Sit-up REPS αα M M-1/3-1/3

Fair index: REPSFair index: REPS..MM1/31/3

(Markovic EJAP ‘04)(Markovic EJAP ‘04)

Body Mass and Push-ups/Sit-ups REPSBody Mass and Push-ups/Sit-ups REPSEvidenceEvidence

MeasureMeasure SubjectsSubjects NN ExponentsExponents SourceSource

Push-upsPush-ups M USMA M USMA cadetscadets 238238

-0.38 (LBM exp = -0.28)

Crowder Crowder MSSEMSSE (abstract ’96)(abstract ’96)

Sit-upsSit-ups M USMA M USMA cadetscadets 238238

-0.26 (LBM exp = -0.24)*

Crowder Crowder MSSEMSSE (abstract ’96)(abstract ’96)

Push-upsPush-ups M college-age M college-age PE studentsPE students 7777 -0.42 Markovic Markovic EJAPEJAP ’04 ’04

Push-upsPush-ups M college-age M college-age PE studentsPE students 7777 -0.30 Markovic Markovic EJAPEJAP ’04 ’04

• Only exponent diff. from -0.33 and only slightly

• No studies on women

Run Time, Effort and %FatRun Time, Effort and %Fat

Age & Wt 5K Handicap ModelAge & Wt 5K Handicap Model– Penalty for fat > credit for extra weightPenalty for fat > credit for extra weight

(Vanderburgh MPEES ’07)(Vanderburgh MPEES ’07)

– With RT/MWith RT/M1/31/3, small remaining bias is , small remaining bias is accounted for by RPE and % fat accounted for by RPE and % fat

(Crecelius JSCR ’08)(Crecelius JSCR ’08)

Body Mass Bias Conclusions for Body Mass Bias Conclusions for Military Physical Fitness TestsMilitary Physical Fitness Tests

Military physical fitness test events favor lighter Military physical fitness test events favor lighter individuals, independent of body fatnessindividuals, independent of body fatness

Distance RunDistance Run– RT RT αα M M1/31/3

– Fair index = Fair index = RT/TRT/T1/31/3

Push-up, Sit-upsPush-up, Sit-ups– REPS REPS αα M M-1/3-1/3

– Fair index = Fair index = REPSREPS..MM1/31/3

Implications/SolutionsImplications/Solutions

Body Mass Bias Penalty - NavyBody Mass Bias Penalty - Navy

Male Female

60 kg 90 kg 45 kg 75 kg Event

Maximum Equivalent Maximum Equivalent

Push-ups 2 min 84 (100) 73 (85) 46 (100) 39 (80)

Curl-ups 2 min 101 (100) 88 (80) 101 (100) 85 (75)

1.5 mi run time 8:55 (100) 10:12 (85) 10:17 (100) 12:11 (85)

Total points (%diff.)

300 250 (16.7%) 300 240 (20%)

(Vanderburgh, Mil Med, 2006)

Body Mass Bias and Occupational Body Mass Bias and Occupational Relevance ConnectionRelevance Connection

The more potent predictors of loaded military The more potent predictors of loaded military task performance (LBM, LBM/DM, upright pull, task performance (LBM, LBM/DM, upright pull, 1RM lift, and absolute VO1RM lift, and absolute VO2max2max) tend to favor ) tend to favor

heavier individuals (LBM, LBM/DM, upright pull, heavier individuals (LBM, LBM/DM, upright pull, 1RM lift, and absolute VO1RM lift, and absolute VO2max2max))

Empirical and theoretical evidence suggests that Empirical and theoretical evidence suggests that common physical fitness test events favor lighter common physical fitness test events favor lighter individualsindividuals

Middle ground?Middle ground?

Occupational Relevance and Body Occupational Relevance and Body Mass BiasMass 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 TestBackpack Run Test(Vanderburgh Mil Med ’00)(Vanderburgh Mil Med ’00)

59 USMA male cadets59 USMA male cadets– Lean, fitLean, fit– Two-mile run timesTwo-mile run times

ModeledModeled effects of alterations in backpack effects of alterations in backpack weight (BW) via ACSM equations on two-mile weight (BW) via ACSM equations on two-mile run timesrun timesBackpack weights of 20-50 kg:Backpack weights of 20-50 kg:– No body mass biasNo body mass bias– Reflected load carriage weights expected of combat Reflected load carriage weights expected of combat

support and/or combat arms service memberssupport and/or combat arms service members

Eliminating bias may be congruent with Eliminating bias may be congruent with occupational relevanceoccupational relevance

Solution 1: Scaled ValuesSolution 1: Scaled Values

Requires calculatorRequires calculatorCreates strange currencyCreates strange currency

SubjectSubject Push-upsPush-ups Body MassBody Mass REPSREPS..MM1/31/3

AA 6767 80 kg80 kg 284.5284.5

BB 7070 68 kg68 kg 281.7281.7

Solution 2: Correction FactorsSolution 2: Correction Factors

Correction Factor (CF) : a dimensionless Correction Factor (CF) : a dimensionless number multiplied by raw scorenumber multiplied by raw score– Based on body massBased on body mass– Uses weight standard (e.g., 50 kg)Uses weight standard (e.g., 50 kg)

Example: woman, 172 lbs, 16:08 RTExample: woman, 172 lbs, 16:08 RT– CF = (125/172)CF = (125/172)1/3 1/3 = 0.90= 0.90– RTadj = 14:31RTadj = 14:31

(Vanderburgh (Vanderburgh Mil MedMil Med ’07) ’07)

Correction Factors Correction Factors Push-ups and Sit-upsPush-ups and Sit-ups

Women 120 130 140 150 160 170 180 190 200 0 1.00 1.01 1.04 1.06 1.08 1.11 1.13 1.15 1.17 1 1.00 1.02 1.04 1.06 1.09 1.11 1.13 1.15 1.17 2 1.00 1.02 1.04 1.07 1.09 1.11 1.13 1.15 1.17 3 1.00 1.02 1.05 1.07 1.09 1.11 1.13 1.15 1.17 4 1.00 1.02 1.05 1.07 1.09 1.12 1.14 1.16 1.18 5 1.00 1.03 1.05 1.07 1.10 1.12 1.14 1.16 1.18 6 1.00 1.03 1.05 1.08 1.10 1.12 1.14 1.16 1.18 7 1.01 1.03 1.05 1.08 1.10 1.12 1.14 1.16 1.18 8 1.01 1.03 1.06 1.08 1.10 1.12 1.14 1.16 1.18 9 1.01 1.04 1.06 1.08 1.10 1.13 1.15 1.17 1.18

(Vanderburgh Mil Med ‘07)

Correction Factors – EffectCorrection Factors – EffectWomen

82 82

69

85 8780

88 91 90

0

25

50

75

100

Push-ups = 35 Sit-ups = 65 2MRT = 19:28

AP

FT

Po

ints

Usi

ng

Ad

just

ed S

core

s

120 lb

150 lb

180 lb

(Vanderburgh Mil Med ‘07)

Solution 3: Balanced TestsSolution 3: Balanced Tests

Balance of body mass bias via events. Balance of body mass bias via events. Example:Example:– 1RM Bench press1RM Bench press– Distance run timeDistance run time

Logistics challengesLogistics challenges

Has not been empirically evaluatedHas not been empirically evaluated

2005 Pump and Run2005 Pump and Run5K run time minus (30 x Bench Press Reps) = adjusted score5K run time minus (30 x Bench Press Reps) = adjusted scoreBench Press weight a % of BW and age-adjustedBench Press weight a % of BW and age-adjustedDespite intent, imposes a substantial body mass biasDespite intent, imposes a substantial body mass biasProposal: correction factors or everyone lifts the same absolute Proposal: correction factors or everyone lifts the same absolute weightweight

(Vanderburgh JSCR 2008)

0

500

1000

1500

2000

35 60 85 110 135

Body Mass (kg)

Ad

just

ed R

un

Tim

e (s

ec)

Women

Men

ConclusionsConclusionsCurrent physical fitness tests of the Army, Navy, and Air Current physical fitness tests of the Army, Navy, and Air Force:Force:– Are not potent determinants of physical military task Are not potent determinants of physical military task

performanceperformance– Impose a physiological bias against heavier service membersImpose a physiological bias against heavier service members

Eliminating body mass bias may be more occupationally Eliminating body mass bias may be more occupationally relevant – must be tested empiricallyrelevant – must be tested empiricallySolutionsSolutions– Scaled valuesScaled values require no change to fitness test protocol but require no change to fitness test protocol but

create strange currencycreate strange currency– Correction factorsCorrection factors provide ease of calculation, preservation of provide ease of calculation, preservation of

original units, and require no equipmentoriginal units, and require no equipment– Balanced fitness testsBalanced fitness tests require equipment but no calculations – require equipment but no calculations –

need validationneed validation

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