an update of the theoretical concept Anaerobic threshold (AT) as determined by VO2max and VLAmax of the working muscle mass of the human body - an update of the theoretical concept A. MADER European Congres Sports Science Rom 1998 Institute for Cardiology and Sports Medicine German Sport University Cologne, Cologne Germany

Basic assumptions About the 30% of body mass are involved in running. Therefore the energy metabolism in the working muscles is the main cause for the dynamic changes of the measurable parameters which are related to energy supply from oxidative phosphorylation (VO2ml/min*kg) and glycolysis (VLa mmol/l*s). Glycolysis and oxidative phosphorylation are activated as a function of the cytosolic phosphorylation state of the high energy phosphate system ([ATP] + [PCr]). As the mechanical power output of the muscle cell decreases the phosphorylation state this activates the metabolic reactions at different levels of the state dephosphorylation. The lactate distribution space is less than 50% of the body volume.

Human body lactic acid distribution space in % body volume VLass 100% 30% 48% 65% Active muscle space Cla(M) Passive lactate space Cla(B) Non H2O space I H2O space Lactate elimination Lactate space VLass Non lactate space II CLass Vol.rel 1) Lactate production in the active space VLaOXss 2) Elimination of lactate in both spaces

Log/lin. steady state activity of oxidative phosphorylation and glycolysis VO2MMK = Michaelis-Menten-Kinetik Oxidative steady state PCr pH = 7.4 VO2 pH=7,0 Non steady state pH=6,8 Proton leak pH=6.2 -DGATP VLass anaerobic threshold Stage of VLa pH=6,6 Chance VO2 ATP VO2 MMK pH=6,4 exhaustion rest

The steady state assumption As oxidative phosphorylation and glycolysis are regulated as a function of the cytosolic [ADP] “gross lactate formation” (Vlass) is a function of the relation between VO2max versus VO2ss. The rate of glycolysis is VLamax (1 +ks2((VO2max-VO2ss)/ks1*VO2ss)3/n) Vlass = + VLaRest ks1  0.035 mmol/l [ADP] ks2  0.2 mmol/l [ADP]

VLaOXmax (mmol/l*min) = (0.035)* VO2ss(ml/min*kg) Measured rate of lactate oxidation, trained and untrained rats (results from DONNOVAN and BROOKS (1983)) (OSS = oxidative steady state) Necessary fuel for maintaining mitochondrial oxidation: VLaOXmax (mmol/l*min) = (0.035)* VO2ss(ml/min*kg) Real carbohydrate (lactate) oxidation is a function of the lactate concentration: VLaOXss (mmol/l*min) = VLaOXmax/(1+ kel/[CLa]2) CLa(mmol/l) is the blood lactate concentration The 50% activity constant kel can be estimated from tracer experiments of DONNOVAN & BROOKS VLaOXmax= f(VO2ma,x, Cla >> 20 mmol/l) Best fit kel = 2.0 kel Blood lactate(mmol/l) OSS => VLaOXmax > VLass

Consequence V(LackPyr) = VLaOXmax - VLaOXss The 50% activity constant kel (CLa) reflects the sentivity of the pyruvate dehydrogenase (PDH). If CLa or CLaSS determines the carbohydrate combustion then “fat combustion” can only take place if there is a “lack of pyruvate production”. The lack of pyruvate expressed as VLass - equivalent is V(LackPyr) = VLaOXmax - VLaOXss In this case the mRQ can be recalculated from CLaSS or Cla(B): ---> %VLaOXss = 100/(1+kel/[CLaSS]2) ---> mRQ = ((100 - %VLaOXss)*0.7 + VLaOXss)/100 ---> for CLaSS = 4.0 mmol/l the mRQ is ~ 0.97

Way of calculation under the “steady state” assumption It is assumed that under all conditions included the complete depletion of PCr the the rectangular area from start to peak VO2 (~ VO2ss) is covered by oxygen uptake and PCr-depletion. This is associated with a certain rate of glycolytic energy sup-ply VLass. VLAss CLa VO2ss Oxidative + alactic power VO2tot(ml/min*kg) = VO2ss + 2.7 * VLass(mmol/l*min)

The problem of the diagnostic of an athletes metabolic capacities ? How can be the aerobic capacity (~ aerobic power related to VO2max (ml/min*kg b.w.)) measured or estimated ? How can be the glycolytic power - defined as “maximal lactate formation rate” (VLamax (mmol/l*s) - determined or estimated ? Does the extent of each of the two powers influence the appearance of the other ? How is the appearance of the so called “anaerobic threshold” (AT) related to the extent of the aerobic and the glycolytic power of an athlete ?

Low endurance, female 400/800m runner 2 x 300m = VO2tot Energy demand glycolytic VO2ss Measured VO2max treadmill max. test 2 min Alactic + oxydat. energy AT Low endurance Glycolytic power ?

Low endurance, female 400/800m runner measured VO2max = 58 ml/min Low endurance, female 400/800m runner measured VO2max = 58 ml/min*kg glycolytic power ? Calcul. mRQ 400m Measured RQ CLa measured VO2max CLa 2 x 300m 74%VO2max Max.test 2Min. AT

Metabolic Profile: Low endurance, female 400/800m runner estimated VO2max = 62 ml/min*kg; glycolytic power = 0.8 mmol/l*s Measured RQ treadmill 600m VLanet 800m VLaOXmax 400m VO2ss %fat comb 300m 2 x 300m Class AT

Energy demand: Highly endurance trained runner: 4mmol speed = 5 Energy demand: Highly endurance trained runner: 4mmol speed = 5.65 m/s, VO2max measured = 76, estimated = 80 m/min*kg BW VLass 1500m Competition 86%VO2max muscle Energy demand V4 VO2ss 2 min max. test Range of Endurance Next slide will appear

Long distance runner, high endurance trained Measured VO2max measured vent. RQ Calculated mRQ d V4 AT

High endurance trainend: VO2max measured 76 ml/min High endurance trainend: VO2max measured 76 ml/min*kg estimated: 80 ml/min*kg, VLamax~ 0.25 mmol/s*l Metabolic RQ 1500m % Fat combustion VLaOXmax Maximum VO2max measured VO2 2Min 2 min Measured RQ 100m 100m CLa VLass Low anaerobic Maxtest V4 Extended range of endurance

High endurance trained %Fat oxidation VO2ss 1500m Measured RQ 600m 100m Lack of pyr Fat VLass Extensive endurance training CLa < 1.25mmol/l AT

Conclusions: - It seems to be possible to recalculate the metabolic pattern according to various test results using spiroergometry and measurement of lactate con-centration after short intensive loads. - The main variables which characterize the athletes metabolic capacities are the estimated maximal oxygen uptake (VO2max) and the maximal rate lactate production (VLAmax).

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