AbdurRakib wrote:
Many athletes inhale pure oxygen after exercise in an attempt to increase muscular re-absorption of oxygen. Measured continuously after exercise, however, the blood lactate levels of athletes who inhale pure oxygen are practically identical, on average, to those of athletes who breathe normal air. The lower the blood lactate level is, the higher the muscular re-absorption of oxygen is.
If the statements above are all true, they most strongly support which of the following conclusions?
(A) Athletes’ muscular re-absorption of oxygen is not increased when they inhale pure oxygen instead of normal air.
(B) High blood lactate levels cannot be reduced.
(C) Blood lactate levels are a poor measure of oxygen re-absorption by muscles.
(D) The amount of oxygen reabsorbed by an athlete’s muscles always remains constant.
(E) The inhaling of pure oxygen has no legitimate role in athletics.
OG2017, CR582, P521
Inhaling Pure Oxygen
Step 1: Identify the QuestionThe phrasing statements…support which of the following conclusions in the question stem indicates that this is an Inference question.
Step 2: Deconstruct the ArgumentMany athletes inhale O to increase MR
BUT: O athletes vs non O athletes: same lactate
low lactate = high MR
Because this is an
Inference question, the argument itself will not contain a conclusion. Instead, it states a series of related facts about the practice of inhaling pure oxygen after exercise. Many athletes believe that it increases muscular reabsorption. However, there is some evidence to the contrary: lactate levels reflect muscular reabsorption, and lactate levels do not change in athletes who inhale pure oxygen.
Step 3: Pause and State the GoalIn an
Inference question, the right answer will be a statement you can prove using
solely the information given in the argument.
Step 4: Work from Wrong to Right(A)
CORRECT. The last sentence of the argument relates muscular reabsorption of oxygen and lactate levels. Athletes with lower lactate levels have higher muscular reabsorption of oxygen. However, athletes who inhale pure oxygen do not have lower lactate levels. It stands to reason that these athletes also do not have higher muscular reabsorption.
(B) According to the argument, inhaling pure oxygen after exercise does not decrease blood lactate levels in athletes. However, it’s too much of a stretch to say that blood lactate levels cannot be reduced at all. It’s possible that they could be reduced through some other means, or in some other population.
(C) There’s no way to tell whether this is the case, using the information provided in the argument. It’s possible that the athletes’ muscular reabsorption of oxygen actually is increased, and their lactate only fails to decrease because blood lactate levels are a poor measure. However, it’s also possible that blood lactate is a good way to measure muscular reabsorption, and these athletes’ muscular reabsorption is not increasing—that is, the evidence from the lactate levels might be correct.
(D) The argument shows that athletes who inhale pure oxygen after exercise do not necessarily increase their muscular reabsorption of oxygen. However, the amount of oxygen reabsorbed by their muscles might not always remain constant. It’s possible that reabsorption changes for other reasons, or even changes at random.
(E) This is a real-world inference, but not an appropriate GMAT inference. Most likely, the person making the argument did so in order to argue against using pure oxygen in athletics. However, this can’t be proven using only what is stated in the argument. The argument only provides evidence that pure oxygen does not aid muscular reabsorbtion. Pure oxygen could have some other legitimate role.