Title

Noninvasive determination of exercise-induced hydrodgen ion threshold through direct optical measurement

UMMS Affiliation

Department of Anesthesiology

Date

3-2008

Document Type

Article

Subjects

Adult; Anaerobic Threshold; Exercise; Extracellular Fluid; Feasibility Studies; Female; *Hand Strength; Humans; Hydrogen-Ion Concentration; Lactic Acid; Male; Models, Biological; *Muscle Contraction; Muscle, Skeletal; Oxygen Consumption; Pulmonary Gas Exchange; Quadriceps Muscle; *Spectroscopy, Near-Infrared; United States

Disciplines

Life Sciences | Medicine and Health Sciences | Physiology

Abstract

The intensity of exercise above which oxygen uptake (Vo2) does not account for all of the required energy to perform work has been associated with lactate accumulation in the blood (lactate threshold, LT) and elevated carbon dioxide output (gas exchange threshold). An increase in hydrogen ion concentration ([H+]) is approximately concurrent with elevation of blood lactate and CO2 output during exercise. Near-infrared spectra (NIRS) and invasive interstitial fluid pH (pHm) were measured in the flexor digitorum profundus during handgrip exercise to produce a mathematical model relating the two measures with an estimated error of 0.035 pH units. This NIRS pHm model was subsequently applied to spectra collected from the vastus lateralis of 10 subjects performing an incremental-intensity cycle protocol. Muscle oxygen saturation (SmO2) was also calculated from spectra. We hypothesized that a H+ threshold could be identified for these subjects and that it would be different from but correlated with the LT. Lactate, gas exchange, SmO2, and H+ thresholds were determined as a function of Vo2 using bilinear regression. LT was significantly different from both the gas exchange threshold (Delta = 0.27 +/- 0.29 l/min) and H+ threshold (Delta = 0.29 +/- 0.23 l/min), but the gas exchange threshold was not significantly different from the H+ threshold (Delta = 0.00 +/- 0.38 l/min). The H+ threshold was strongly correlated with LT (R2 = 0.95) and the gas exchange threshold (R2 = 0.85). This initial study demonstrates the feasibility of noninvasive pHm estimations, the determination of H+ threshold, and the relationship between H+ and classical metabolic thresholds during incremental exercise.

Rights and Permissions

Citation: J Appl Physiol. 2008 Mar;104(3):837-44. Epub 2007 Dec 20. Link to article on publisher's site

DOI of Published Version

10.1152/japplphysiol.00849.2007

Related Resources

Link to Article in PubMed

Journal Title

Journal of applied physiology (Bethesda, Md. : 1985)

PubMed ID

18096753