Question

Explain what is the physiological reason for why metabolic consequences (e.g. changes in exercise intensity, substrate utilization, and blood lactate levels) result in changes in ventilation during a graded maximal exercise test?

Answer 1

Ans) Analysis of [La−]b is often used in clinical exercise testing for exercise prescription and assessments of the effects of therapy and physical training.

- Thus, it is important for clinicians to understand the pathological [La−]b response as well as the normal [La−]b response to exertion. In response to progressive incremental exercise, [La−]b will increase in an exponential manner once LT has been exceeded. Various methods are valid for describing this curvilinear [La−]b response with a single point, although LT is highly individualized.

- An individual's endurance performance is well correlated with his or her LT, and endurance training improves LT.

- While [La−]b is significantly elevated (≈8–10 mM) following a progressive, incremental exercise test to volitional exhaustion, the highest [La−]b values (≈15–25 mM) are typically observed 3–8 minutes after “all-out” maximal exertion of 30–120 seconds. MCTs provide the primary of three routes by which La− transport proceeds across the sarcolemma and RBC membrane. In RBC membranes specifically, La− flux occurs mainly via MCT1. At rest and under most exercise conditions, whole blood [La−] values are on average 70% of corresponding plasma [La−] values, and thus care must be taken to ensure that the correct measurement is being made during analysis. When analyzing the validity of a [La−]b-measuring instrument, it is critical that comparisons are made with the criterion/reference enzymatic method, not simply among analyzers.

- The Lactate Pro has performed better than many La− analyzers when careful comparisons to the criterion/reference enzymatic method have been made. Overall, it is advantageous for clinicians to have a thorough understanding of [La−]b responses, blood La− transport and distribution, and [La−]b analysis. While an elevated [La−]b may be indicative of ischemia or hypoxemia, it may also be a “normal” physiological response to exertion.