What is the purpose of metabolic calculations?

Estimate energy expenditure during steady state exercise.

What are metabolic units?

Absolute vs. Relative VO2 units; Absolute units – independent of body weight; liters of O2 per minute (l.min-1); Relative units – dependent on body weight; milliliters of O2 per kg per minute (ml.kg-1.min-1); Good for comparing VO2 between subjects of differing body weights; Be able to convert between absolute and relative!

If two people have the same absolute VO2, who has greater relative VO2?

If a 50 kg person and a 70 kg person have the same absolute VO2 (2 L/min): 2 L/min = 2000 ml/min; 2000 ml/min ÷ 50 kg = 40 ml/kg/min; 2000 ml/min ÷ 70 kg = 28.6 ml/kg/min.

What is gross vs net VO2?

Gross VO2: total VO2 including resting VO2; Net VO2: VO2 in excess of resting VO2; associated with exercise; Net VO2 = Gross VO2 – resting VO2.

What are METs?

METs: Metabolic equivalents; 1 MET = resting metabolism; 2 METs = 2x resting metabolism; 1 MET = 3.5 ml.kg-1.min-1.

How is energy expenditure expressed?

Energy expenditure during exercise is commonly reported as Kilocalories per min (kcals . min-1); Application to Weight Control / Energy Balance; 1 lb of fat ~ 3500 kcal.

What is the relationship between VO2 and caloric expenditure?

1 Liter of O2 = ~5 kcals (5 kcal/L); Can calculate caloric expenditure from VO2; If VO2 = 2.0 L/min, caloric expenditure = 2.0 L/min * 5 kcal/L = 10.0 kcal/min; Also: 1 MET = 1.0 kcal . kg-1 . hr-1; Important: When determining the caloric cost of an activity, use Net VO2.

What is the ACSM walking equation?

Accurate for speeds: 50-100 m/min; 1.9-3.7 mph; Gives relative VO2 (ml.kg-1.min-1); VO2 = Horizontal + Vertical + Resting; VO2 = 0.1(speed) + 1.8(speed)(grade) + 3.5.

What do the walking equation constants represent?

0.1 = O2 needed to move 1 kg horizontally 1 m; 1.8 = O2 needed to move 1 kg vertically 1 m; 3.5 = resting VO2; 1 MET.

What is the ACSM running equation?

Accurate for speeds >134 m/min; >5.0 mph; VO2 = 0.2(speed) + 0.9(speed)(grade) + 3.5.

What do the running equation constants represent?

0.2 = horizontal cost; 0.9 = vertical cost; 3.5 = resting VO2; 1 MET.

How is work rate calculated?

Work rate (power) = resistance (kg) * distance (m) * frequency (rpm); 1 Watt = 6.12 kg.m.min-1; Monark leg ergometer distance = 6 m; Monark arm ergometer distance = 2.4 m.

What is the ACSM leg cycling equation?

VO2 = 1.8(work rate) / body mass in kg + 7; Most accurate for loads 300-1200 kg.m.min-1; Constants: 1.8 (cycling cost); 3.5 (unloaded cycling); 3.5 (resting VO2).

What is the ACSM arm cycling equation?

VO2 = 3(work rate) / body mass in kg + 3.5; Most accurate for loads 150-750 kg.m.min-1; Constants: 3 (cycling cost); 3.5 (resting VO2); unloaded cycling negligible.

What is the ACSM stepping equation?

VO2 = 0.2(step rate) + 1.33(1.8)(step rate)(step height) + 3.5; Step rate = steps/min; Step height in meters; Constants: 0.2 (horizontal); 1.8 (vertical); 1.33 (descending cost).

How do you calculate caloric expenditure from VO2?

Convert gross to net VO2; Convert ml/kg/min to L/kg/min; Multiply by body mass; Multiply by 5 kcal/L.

Example caloric calculation

30 ml/kg/min → 26.5 net; 0.0265 L/kg/min * 70 kg = 1.855 L/min; 1.855 * 5 = 9.3 kcal/min.

Case study: net kcal calculation

17.4 ml/kg/min → net 13.9; 0.0139 L/kg/min * 75 = 1.04 L/min; 1.04 * 5 = 5.21 kcal/min.

Case study: treadmill 0% grade

VO2 = 8.04 ml/kg/min; 0.64 L/min; 3.2 kcal/min; 300 kcal / 3.2 = 93.8 min.

Case study: treadmill 2% grade

VO2 = 10.9 ml/kg/min; 0.87 L/min; 4.35 kcal/min; 300 kcal / 4.35 = 69 min.

Case study: cycling VO2

Work rate = 1350 kg.m.min-1; VO2 = 35.6 ml/kg/min.

Case study: watts calculation

9 METs = 31.5 ml/kg/min; 70% = 22.05; Work rate = 627.1 kg.m.min-1; 627.1 / 6.12 = 102.5 Watts.

Case study: return to work decision

Capacity = 25 ml/kg/min → 8.75 kcal/min; Work = 7-8 kcal/min; >50% of capacity → not ready to return.

What are risks of exercise testing?

Peak Exercise Tests or Symptom-limited Graded Exercise tests; includes patients with disease; Risk for all CV events: 0.06%.