Interpretational considerations when using healthy individuals as a surrogate for elite athletes in response to vaccination

Reply to Ewell and Abbotts

“…to the editor : We have reviewed the letter submitted by Ewell and Abbotts ( 1 ) regarding our article entitled “Recent COVID-19 vaccination has minimal effects on the physiological responses to graded exercise in physically active healthy people” ( 2 ) that was recently published in the Journal of Applied Physiology . The main point raised in this letter is that data collected from nonathletic healthy participants should be interpreted with caution when applied to the context of elite sport.…”

“…Although we agree with this assertion and had stated in our manuscript that these experiments should be replicated in elite/highly trained athletes, we have some misgivings about the “considerations” proposed by Ewell and Abbotts ( 1 ). The core point of their argument is that the participants used in our study had “poor” levels of aerobic fitness in accordance with American College of Sports Medicine (ACSM) criteria and that “elite athletes have more robust immune responses compared to poorly conditioned individuals.” It is important to highlight that the statement by Ewell and Abbotts ( 1 ) that “the mean predicted maximal oxygen uptake (V̇ o 2max ) of the study population was 40.7 mL/kg/min and would be considered ‘Poor’ according to the American College of Sports Medicine (ACSM)” only applies to healthy men aged 20–29 yr ( 3 ). It appears, therefore, that Ewell and Abbotts ( 1 ) have overlooked two facts.…”

“…The core point of their argument is that the participants used in our study had “poor” levels of aerobic fitness in accordance with American College of Sports Medicine (ACSM) criteria and that “elite athletes have more robust immune responses compared to poorly conditioned individuals.” It is important to highlight that the statement by Ewell and Abbotts ( 1 ) that “the mean predicted maximal oxygen uptake (V̇ o 2max ) of the study population was 40.7 mL/kg/min and would be considered ‘Poor’ according to the American College of Sports Medicine (ACSM)” only applies to healthy men aged 20–29 yr ( 3 ). It appears, therefore, that Ewell and Abbotts ( 1 ) have overlooked two facts. First, that V̇ o 2max scores are categorized according to age and sex; and second, that we recruited equal numbers of male and female participants aged 24– 43 yr.…”

“…In this context, a V̇ o 2max value of 40.7 mL/kg/min would actually be considered “good” and “excellent” for women aged 20–29 and 30–39 yr, respectively ( 2 ). Given that approximately three-fourth of our participants had age- and sex-adjusted V̇ o 2max scores considered “good,” “excellent,” or “superior,” we contend that our participants were not “poorly conditioned” as implied by Ewell and Abbotts ( 1 ). We do agree that elite athletes, or at least very highly trained individuals, have more robust immune responses than poorly conditioned individuals.…”

“…Ewell and Abbotts ( 1 ) rightly pointed out that elevations in the heart rate response to exercise after COVID-19 vaccination should have been accompanied by either increases in cardiac output or reductions in stroke volume. We believe that this is due to the methods used to measure stroke volume and cardiac output during exercise, which were estimated indirectly using heart rate and oxygen uptake by respiratory gas exchange.…”