Duncan Macfarlane IHP, HKU Parts of this lecture were based on lecture notes provided by the Lindsay Carter Anthropometric Archive, AUT, NZ

Transcription

1 Body composition assessment issues in athletes 1 Duncan Macfarlane IHP, HKU Parts of this lecture were based on lecture notes provided by the Lindsay Carter Anthropometric Archive, AUT, NZ

2 LEARNING OUTCOMES: 1. Why examine body composition 2. Understand the different levels of assessment of body composition 3. Limitations/benefits of using skinfolds 4. Limitations/benefits of using bioelectric impedance (BIA) 5. Limitations/benefits of using of DXA

3 WHY ASSESS BODY COMPOSITION: 1. Body composition is a component of fitness 2. It can be a screening tool to assess health risk factors 3. To monitor progress and effectiveness of a training program 4. It can be a screening tool to determine what sport someone is most suited to (???)

4 My SomatoMac ipad project 4

5 Basic Two compartment model TBM = FM + LBM 5 FM = dissectible adipose tissue + fat, including subcutaneous adipose tissue & deep adipose tissue in stores like large intestine & that surrounding joints. LBM = all other tissue + small amount of fat contained within.

6 Does fat free mass = lean body mass? 6 NO, FFM implies all other tissue minus all fat. But practically this is not possible to achieve since fat is present inside tissues such as bone & between fibres & fasciculi of muscle.

7 Models of body composition Two-compartment model is used for sport science fat mass and fat-free mass

8 Methods to assess body fat Direct methods: Dissection 8 Indirect methods: Hydrostatic weighing Dual energy x-ray absorptiometry (DEXA, DXA) Doubly indirect methods: Body mass index (BMI) = yuck! Bioelectrical impedance analysis (BIA) Skinfold/circumference method

9 BMI Mass (kg) / square of Height (m) Does NOT distinguish FAT v MUSCLE 9

10 Body Mass=75 kg Height= 1.66m BMI= 27.2 Overweight?? 10

11 Levels of assessment 11

12 Jan Clarys et al. LEVEL 1: DIRECT ASSESSMENT Direct anatomical evidence of individual differences. The adipose tissue free tissue mass from 7 female and 6 male unembalmed cadavers dissected 48 hours after demise. Muscle % Bone % Residual %

13 Level III Skinfold regression equations 13 Follow protocol carefully. Between 150 & 200 equations available. Choose an equation carefully based on correct population.

14 Skinfold assumptions (lead to prediction errors) Constant compressibility of skin/tissues. Two identical skinfolds can have markedly difference subcutaneous fat due in part to different compressibility (eg. front thigh, but supraspinale Brussels cadaver study) Skin thickness is constant (within/between people). There is fixed adipose tissue patterning across limbs (and people). Subject 1 Subject SScap Abd SSpin Tri Bic Thi Calf Constant fat fraction in adipose tissue. Fixed proportion of internal to external fat deposits. 14

15 Anthropometry Uses multiple measures. Skinfolds, girths, lengths of bones, breadths of bones, height and weight together. Restricted (15) and Full profile (42) measures. Can take time (10-30min). 15

16 It does matter where you take the skinfolds! Patria Hume and Mike Marfell-Jones

17 Hume et al study

18 Methods Cross-sectional quantitative 12 subjects 27.1 ± 6.5 years ± 7.4 cm 77.8 ± 12.7 kg 8 ISAK-specified skinfold sites 8 points about ISAK = 9 points in 1-cm grid pattern 3 x each grid point 2 x ISAK Criterion Level 4 measurers (TEM<1%) Harpenden skinfold 0.1 mm accuracy

19 Hume et al study

20 Hume et al study

21 Triceps Biceps Subscapular Red shows significant differences Subscapular showed least # of differences Size of the circle is the size of the Cohen effect Iliac crest Supraspinale Abdominal Abdominal showed most # of differences Iliac crest shows an anterior trend Thigh Calf

22 Data on HK Young Adults Body Fat Equa,on Mean Pred %BF Mean DXA (NH) B_A Bias B_A LoA PE % CV % Effect Size Males Sloan Wilmore Katch Durnin Withers 1987a Lean 1996a Lean 1996b Peterson Garcia MACFARLANE Females Sloan Katch Wilmore Durnin Pollock 1975a Lewis Jackson 1980a Jackson 1980b Thorland Withers 1987b Withers 1987c/d Lean 1996a Lean 1996b Peterson MACFARLANE

23 Level III Anthropometry 23 Advantages: Convenient and cheap method. Equipment is portable. Relatively non-invasive? Quite good for follow-up analysis Disadvantages: Numerous assumptions - Can take a lot of time for 42 Full sites even for 15 Restricted sites Many equations they do not agree (%Body Fat equations = wrong; keep as a simple Sum of Skin-Folds) Requires a GOOD measurer (ISAK L1)

24 Level III Bioelectrical Impedance 24 Measures total body water, not body fat. Uses relationship between H20 and fat. Depends on equation in black box.

25 Level III Bioelectrical impedance 25 Hand to foot lying. Hand to hand standing. Foot to foot standing. Muscle electrical activity filtered out?

26 Level III Bioelectrical impedance 26 Passes electrical current through electrodes placed on hand, wrist, ankle, and foot. Measures resistance to current. Muscle holds more water so resistance is less than in fat. Measures total body water which can be used to measure fat free mass based on assumption percentage of total body water in fat free mass (73%).

27 Level III Bioelectrical impedance 27 Advantages: Convenient and rapid method. Equipment is portable. Non-invasive. Correlates well with hydrostatic weighing (0.93). Disadvantages: Subject must be normally hydrated. Software is not uniform across machines (racial norms?) 3-5 % error? even higher? - does it monitor changes over time? (eg. v DXA?)

28 Are BIA machines reliable? - Yes but MUST be under identical conditions 28

29 Macfarlane study: DXA v BIA to track changes over 3 months 29! Table!2.!!Baseline,!change1score!after!intervention!and!statistics!for!BIA!and!DXA! measurements,!as!well!as!comparisons!of!change1scores!(delta)!between!devices:! means!±!sd.!!! Baseline,! g! Change!after! intervention,! g,!(%)! Change:!! p1value!! (t1test)! Change:! Effect!size! Weight!(g)! 65287!±! 13603! 1313!±!1500! (10.5%)! 0.008! 0.20! (small)! Fat!DXA!(g)! 21981!±! 1802!±!1096! <0.001! 0.16! 6589! (13.6%)! (small)! Fat!BIA!(g)! 19554!±! 1485!±!1539! <0.001! 0.17! 6898! (12.5%)! (small)! delta1fat!!! 0.003! 0.72! (DXA!v!BIA)! (large)! Muscle!DXA! 42561!±! 477!±!966! <0.001! 0.09! (g)! 9485! (+1.1%)! (trivial)! Muscle!BIA! 43255!±! 84!±!1201! 0.425! 0.08! (g)! 9967! (+0.2%)! (trivial)! delta1muscle!!! <0.001! 0.79! (DXA!v!BIA)! (large)! Bone!DXA!(g)! 2143!±! 7!±!41! 0.052! 0.08! 392! (+0.3%)! (trivial)! Bone!BIA!(g)! 2543!±! 14!±!91! 0.074! 0.11! 496! (+0.6%)! (trivial)! delta1bone!!! 0.392! 0.93! (DXA!v!BIA)! (large)!! Correlation,! r! (p1value)!!!! 0.511! (<0.001)!!! 0.362! (<0.001)!!! 0.172! (0.047)! Baseline: %BF by DXA = 33.7% %BF by BIA = 30.0% = 3.7% higher by DXA %muscle by DXA = 65.2% %muscle by BIA = 66.3% = 1.1% lower by DXA

30 Macfarlane study: DXA v BIA to track changes over 3 months 30! Table!2.!!Baseline,!change1score!after!intervention!and!statistics!for!BIA!and!DXA! measurements,!as!well!as!comparisons!of!change1scores!(delta)!between!devices:! means!±!sd.!!! Baseline,! g! Change!after! intervention,! g,!(%)! Change:!! p1value!! (t1test)! Change:! Effect!size! Weight!(g)! 65287!±! 13603! 1313!±!1500! (10.5%)! 0.008! 0.20! (small)! Fat!DXA!(g)! 21981!±! 1802!±!1096! <0.001! 0.16! 6589! (13.6%)! (small)! Fat!BIA!(g)! 19554!±! 1485!±!1539! <0.001! 0.17! 6898! (12.5%)! (small)! delta1fat!!! 0.003! 0.72! (DXA!v!BIA)! (large)! Muscle!DXA! 42561!±! 477!±!966! <0.001! 0.09! (g)! 9485! (+1.1%)! (trivial)! Muscle!BIA! 43255!±! 84!±!1201! 0.425! 0.08! (g)! 9967! (+0.2%)! (trivial)! delta1muscle!!! <0.001! 0.79! (DXA!v!BIA)! (large)! Bone!DXA!(g)! 2143!±! 7!±!41! 0.052! 0.08! 392! (+0.3%)! (trivial)! Bone!BIA!(g)! 2543!±! 14!±!91! 0.074! 0.11! 496! (+0.6%)! (trivial)! delta1bone!!! 0.392! 0.93! (DXA!v!BIA)! (large)!! Correlation,! r! (p1value)!!!! 0.511! (<0.001)!!! 0.362! (<0.001)!!! 0.172! (0.047)! NOTE: Mass dropped only 313g, but Fat loss was 802g, with Muscle gain 477g = do not use weight scales alone! BIA only measured 61% of the Fat losses seen by DXA BIA only measured 18% of the Muscle gains seen by DXA

31 WHY is BIA different to DXA: All mainly due to different assumptions and different calibrations lack of Direct Level 1 criterion comparisons Eg. Max car speed = distance/time ; eg. 1km in 18sec = 200kph Pat Fox + = 250kph? NO the car s speedometer was not calibrated correctly

32 Level II methods: Indirect measurement and use of assumptions based on qualitative measures 32 Underwater weighing - accurate, cheaper, uncomfortable, current gold standard? Medical imaging, CT scan, MRI accurate, $! DXA - accurate but $!, future gold standard?

33 Dual energy X-ray absorptiometry (DEXA) 33 Primarily used to determine bone mineral density (BMD). Can measure regional or total body composition (often using a Fan Beam X- ray very low dose) With further research, could be new gold standard? some say it already is the gold standard?

34 Advantages: +/-2% error fat, +/-1% error bone? better now? Directly gives % fat without relying on assumed density. Low radiation dose. Minimal effort by subject. Minimal amount of time needed to perform. Gives total or regional values. Dual energy X-ray absorptiometry (DXA) Technician does not have to be trained extensively. Disadvantages: Costs HK$600,000 per scanner. Computer software is not uniform for every scanner. Software values do not account for extremes of % body fat. Software is based on adult values, not all races have norms Very obese hard to fit on table (mirror half of them?) 34

35 Example of Output 35

36 Details of Output (BMC/BMD) 36

37 Details of Output (fracture risk) 37

38 Details of Output (body comp) 38

39 How reliable is DXA? 39

40 But differences can be seen between two scans 40 Female Athlete scanned twice within 15 minutes: 1 st scan: % Body Fat = 22.5% 2 nd scan: % Body Fat = 21.5% In comparison her InBody BIA value = 12% = Huge difference (and very few elite females are at 12%!!) Myself scanned twice within 15 minutes: 1 st scan: % Body Fat = 22.8% 2 nd scan: % Body Fat = 23.9% - these 1% total difference in DXA %body-fat are HIGH (not sure if this is due to our aging DXA) We have just purchased a new Hologic DXA and happy to check values compared to the HKSI DXA

41 But differences can be due to software changes too! In 2009 Hologic changed their DXA software due to the USA NHANES analysis study (Kelly et al, 2009, PLoS ONE) to increase %body fat by about 4-5%!! - So comparisons with previous pre-2009 data = almost impossible - aarrgghh! 41 Female Elite Athlete same scan but different software (+/- NHANES adjustment): Scan using 2008 (pre-nhanes) analysis: % Body Fat = 16.7% (51.5kg Lean tissue) Scan using 2009 (NHANES) analysis: % Body Fat = 21.2% (48.6kg Lean tissue) = +4.5%BF = Huge difference (due entirely to different calibration/analysis) (another female: pre-nhanes=38.3% v NHANES=41.6 = +3.3%BF difference) Male non-elite same scan but different software (+/- NHANES adjustment): Scan using 2008 (pre-nhanes) analysis: % Body Fat = 16.1% (64.2kg Lean tissue) Scan using 2009 (NHANES) analysis: % Body Fat = 20.7% (60.5kg Lean tissue) = +4.6%BF = Huge difference (due entirely to different calibration/analysis) (another male: pre-nhanes=11.8% v NHANES=16.6% = +4.8%BF difference)

42 How to minimize variations between scans Two good studies by Nana et al (MSSE, 2012 & 2013) showing Fat mass here only concluded none of the changes in body fat were substantial but consuming the meal did increase lean mass to a small degree

43 How to minimize variations between scans Nana et al (MSSE, 2013) 43

44 How to minimize variations between scans Nana et al (MSSE, endurance) 44

45 How to minimize variations between scans Nana et al (2013) concluded: Fat mass showed small/minimal changes after exercise in both strength & endurance athletes 45 Lean mass also showed small/minimal changes after exercise in both strength & endurance athletes Despite these small/minimal changes they still suggest athletes should fast overnight and perform a DXA when completely rested in the morning with NO exercise prior Also hydration status is important (euhydration) ideally using specific gravity of urine checked, and void bladder before scan - These rules were derived for statistical reasons rather than for functional reasons to me the differences are small -?? Ideally fast overnight, but if not practical no exercise prior and no meal within 2hr?, and ensure a constant level of hydration = more critical