Acute moderate normobaric hypoxia does not modify circulating thyroid hormone concentrations induced by one hour of head out cold-water immersion

This study tested the hypothesis that acute moderate normobaric hypoxia augments circulating thyroid hormone concentrations during and following one hour of cold head out water immersion (HOWI), compared to when cold HOWI is completed during normobaric normoxia. In a randomized crossover single blind design, 12 healthy adults (27 ± 2 y, 2 women) completed one hour of cold (22.0±0.1⁰C) HOWI breathing either normobaric normoxia (FiO2 = 0.21) or normobaric hypoxia (FiO2 = 0.14). Free and total thyroxine (T3) and triiodothyronine (T4), and thyroid stimulating hormone (TSH) concentrations were measured in venous blood samples obtained before (baseline), during (15-, 30-, and 60-min), and 15 min following HOWI (post-), and were corrected for changes in plasma volume. Arterial oxyhemoglobin saturation and core (rectal) temperature were measured continuously. Arterial oxyhemoglobin saturation was lower during hypoxia (90 ± 3%) compared to normoxia (98 ± 1%, p<0.001). Core temperature fell from baseline (normoxia: 37.2 ± 0.4°C, hypoxia: 37.2 ± 0.4°C) to post- cold HOWI (normoxia: 36.4 ± 0.5°C, hypoxia: 36.3 ± 0.5°C, p<0.001) in both conditions but did not change differently between conditions (condition x time: p=0.552). Circulating TSH, Total T3, Free T4, Total T3, and Free T4 concentrations demonstrated significant main effects of time (all p≤0.024), but these changes did not differ between normoxic and hypoxic conditions (condition x time: all p³0.163). These data indicate that acute moderate normobaric hypoxia does not modify the circulating thyroid hormone response during one hour of cold HOWI.

Increased spleen volume provoked by temperate head-out-of-water immersion

This study tested the hypotheses that 1) spleen volume increases during head-out-of-water immersion (HOWI) and returns to pre-HOWI values postdiuresis, and 2) the magnitude of apnea-induced spleen contraction increases when preapnea spleen volume is elevated. Spleen volume was measured before and after a set of five apneas in 12 healthy adults (28 ± 5 yr, 3 females) before, during (at 30 and 150 min), and 20 min after temperate temperature (36 ± 1°C) HOWI. At each time point, spleen length, width, and thickness were measured via ultrasound, and spleen volume was calculated using the Pilström equation. Compared with pre-HOWI (276 ± 88 mL), spleen volume was elevated at 30 (353 ± 94 mL, P < 0.01) and 150 (322 ± 87 mL, P < 0.01) min of HOWI but returned to pre-HOWI volume at post-HOWI (281 ± 90 mL, P = 0.58). Spleen volume decreased from pre- to postapnea bouts at each time point (P < 0.01). The magnitude of reduction in spleen volume from pre- to postapneas was elevated at 30 min of HOWI (-69 ± 24 mL) compared with pre-HOWI (-52 ± 20 mL, P = 0.04) but did not differ from pre-HOWI at 150 min of HOWI (-54 ± 16 mL, P = 0.99) and post-HOWI (-50 ± 18 mL, P = 0.87). Thus, spleen volume is increased throughout 180 min of HOWI, and whereas apnea-induced spleen contraction is augmented after 30 min of HOWI, the magnitude of spleen contraction is unaffected by HOWI thereafter.

A Narrative Analysis of the Progression in the Top 100 Marathon, Half-Marathon, and 10-km Road Race Times from 2001 to 2019

PURPOSE

This study aimed to characterize and describe finishing time trends of the fastest 100 performers in the men's and women's marathon, half-marathon, and road 10-km each year from 2001 to 2019 and assess the underlying basis for recent performance improvements.

METHODS

The top 100 performers for each sex, event, and year were partitioned into four arbitrary ranking groups: 1-10, 11-25, 26-50, and 51-100. The percent improvement in mean performance time for each year beyond 2001 was calculated for each ranking group, event, and sex. Multiple linear regression was also used to determine improvement trend for each ranking group, both sexes, and all events for each 3-yr period between Olympic years.

RESULTS

In total, 11,400 performances in the marathon, half-marathon, and 10-km road races from 2001 to 2019 were analyzed. The 3-yr period preceding the original date of the Tokyo Olympics (2017-2019) accounted for 44% and 35% of the overall improvement in marathon time from 2001 to 2019 for women and men, respectively. The years 2017-2019 featured the largest average improvement of any 3-yr period and was the only period where nearly every ranking group in every event for both sexes improved.

CONCLUSIONS

The results suggest that recent world record performances are a result of overall circumstances affecting road racing (e.g., shoe technology) rather than the outstanding physiology of individual top runners, per se.

Nedocromil sodium and diphenhydramine HCl ameliorate exercise-induced arterial hypoxemia in highly trained athletes

INTRODUCTION

Exercise-induced arterial hypoxemia (EIAH) has been observed in highly trained endurance athletes during near maximal exercise, which may be influenced by a histamine-mediated inflammatory response at the pulmonary capillary-alveolar membrane. In order to test this hypothesis, we examined whether the mast cell stabilizer nedocromil sodium (NS) and H1 -receptor antagonist diphenhydramine HCL (DH) would ameliorate EIAH and mitigate the drop in arterial oxyhemoglobin saturation (Sa O2 ) during intensive exercise.

METHODS

Seven highly trained male cross country runners (age, 21 ± 2 years; V̇O2max , 74.7 ± 3.5 ml·kg-1 ·min-1 ) participated in the study. All subjects completed a maximal exercise treadmill test to exhaustion, followed by three 5-min constant-load exercise bouts at 70%, 80%, and 90% V̇O2max . Prior to testing, subjects received either placebo (PL), NS, or DH.

RESULTS

Compared to PL, there was a significant treatment effect on Sa O2 (p < 0.001) for both NS and DH during both constant-load exercise and at V̇O2max . Post hoc tests revealed Sa O2  values, compared to PL, were significantly higher at V̇O2max and during DH trials and higher with NS at constant-load intensities except at 70% (p = 0.13).

CONCLUSION

The findings provide further evidence that histamine contributes directly or indirectly to the development of EIAH during intense exercise in highly trained athletes.

Access to and safety of COVID-19 convalescent plasma in the United States Expanded Access Program: A national registry study

BACKGROUND

The United States (US) Expanded Access Program (EAP) to coronavirus disease 2019 (COVID-19) convalescent plasma was initiated in response to the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19. While randomized clinical trials were in various stages of development and enrollment, there was an urgent need for widespread access to potential therapeutic agents. The objective of this study is to report on the demographic, geographical, and chronological characteristics of patients in the EAP, and key safety metrics following transfusion of COVID-19 convalescent plasma.

METHODS AND FINDINGS

Mayo Clinic served as the central institutional review board for all participating facilities, and any US physician could participate as a local physician-principal investigator. Eligible patients were hospitalized, were aged 18 years or older, and had-or were at risk of progression to-severe or life-threatening COVID-19; eligible patients were enrolled through the EAP central website. Blood collection facilities rapidly implemented programs to collect convalescent plasma for hospitalized patients with COVID-19. Demographic and clinical characteristics of all enrolled patients in the EAP were summarized. Temporal patterns in access to COVID-19 convalescent plasma were investigated by comparing daily and weekly changes in EAP enrollment in response to changes in infection rate at the state level. Geographical analyses on access to convalescent plasma included assessing EAP enrollment in all national hospital referral regions, as well as assessing enrollment in metropolitan areas and less populated areas that did not have access to COVID-19 clinical trials. From April 3 to August 23, 2020, 105,717 hospitalized patients with severe or life-threatening COVID-19 were enrolled in the EAP. The majority of patients were 60 years of age or older (57.8%), were male (58.4%), and had overweight or obesity (83.8%). There was substantial inclusion of minorities and underserved populations: 46.4% of patients were of a race other than white, and 37.2% of patients were of Hispanic ethnicity. Chronologically and geographically, increases in the number of both enrollments and transfusions in the EAP closely followed confirmed infections across all 50 states. Nearly all national hospital referral regions enrolled and transfused patients in the EAP, including both in metropolitan and in less populated areas. The incidence of serious adverse events was objectively low (<1%), and the overall crude 30-day mortality rate was 25.2% (95% CI, 25.0% to 25.5%). This registry study was limited by the observational and pragmatic study design that did not include a control or comparator group; thus, the data should not be used to infer definitive treatment effects.

CONCLUSIONS

These results suggest that the EAP provided widespread access to COVID-19 convalescent plasma in all 50 states, including for underserved racial and ethnic minority populations. The study design of the EAP may serve as a model for future efforts when broad access to a treatment is needed in response to an emerging infectious disease.

TRIAL REGISTRATION

ClinicalTrials.gov NCT#: NCT04338360.

Cutaneous microvascular vasodilatory consequences of acute consumption of a caffeinated soft drink sweetened with high-fructose corn syrup

This study tested the hypotheses that compared to drinking water, consumption of a caffeinated soft drink sweetened with high‐fructose corn syrup (HFCS) attenuates the cutaneous vasodilatory response to local skin heating without (Protocol 1) and following ischemia‐reperfusion injury (Protocol 2). In a randomized, counterbalanced crossover design, 14 healthy adults (25 ± 3 year, 6 women) consumed 500 ml of water (water) or a caffeinated soft drink sweetened with HFCS (Mtn. Dew, DEW). Thirty minutes following beverage consumption local skin heating commenced on the right forearm (Protocol 1), while on the left forearm ischemia‐reperfusion commenced with 20 min of ischemia followed by 20 min of reperfusion and then local skin heating (Protocol 2). Local skin heating involved 40 min of heating to 39℃ followed by 20 min of heating to 44℃. Skin blood flow (SkBf, laser Doppler) data were normalized to mean arterial pressure and are presented as a cutaneous vascular conductance (CVC) and as percentage of the CVC response during heating to 44℃ (%CVC_max). Protocol 1: During local heating at 39℃, no differences were observed in CVC (water: 2.0 ± 0.6 PU/mmHg; DEW: 2.0 ± 0.8 PU/mmHg, p = 0.83) or %CVC_max (water: 59 ± 14%; DEW 60 ± 15%, p = 0.84) between trials. Protocol 2: During local skin heating at 39℃, no differences were observed in CVC (water: 1.7 ± 0.5 PU/mmHg; DEW: 1.5 ± 0.5 PU/mmHg, p = 0.33) or %CVC_max (water: 64 ± 15%; DEW 61 ± 15% p = 0.62) between trials. The cutaneous microvascular vasodilator response to local heating with or without prior ischemia‐reperfusion injury is not affected by acute consumption of a caffeinated soft drink sweetened with HFCS.

Prevalence of Clinical and Subclinical Myocarditis in Competitive Athletes With Recent SARS-CoV-2 Infection: Results From the Big Ten COVID-19 Cardiac Registry

Question

What is the prevalence of myocarditis in competitive athletes after COVID-19 infection, and how would different approaches to screening affect detection?

Findings

In this cohort study of 1597 US competitive collegiate athletes undergoing comprehensive cardiovascular testing, the prevalence of clinical myocarditis based on a symptom-based screening strategy was only 0.31%. Screening with cardiovascular magnetic resonance imaging increased the prevalence of clinical and subclinical myocarditis by a factor of 7.4 to 2.3%.

Meaning

These cardiac magnetic resonance imaging findings provide important data on the prevalence of clinical and subclinical myocarditis in college athletes recovering from symptomatic and asymptomatic COVID-19 infections.

Importance

Myocarditis is a leading cause of sudden death in competitive athletes. Myocardial inflammation is known to occur with SARS-CoV-2. Different screening approaches for detection of myocarditis have been reported. The Big Ten Conference requires comprehensive cardiac testing including cardiac magnetic resonance (CMR) imaging for all athletes with COVID-19, allowing comparison of screening approaches.

Objective

To determine the prevalence of myocarditis in athletes with COVID-19 and compare screening strategies for safe return to play.

Design, Setting, and Participants

Big Ten COVID-19 Cardiac Registry principal investigators were surveyed for aggregate observational data from March 1, 2020, through December 15, 2020, on athletes with COVID-19. For athletes with myocarditis, presence of cardiac symptoms and details of cardiac testing were recorded. Myocarditis was categorized as clinical or subclinical based on the presence of cardiac symptoms and CMR findings. Subclinical myocarditis classified as probable or possible myocarditis based on other testing abnormalities. Myocarditis prevalence across universities was determined. The utility of different screening strategies was evaluated.

Exposures

SARS-CoV-2 by polymerase chain reaction testing.

Main Outcome and Measure

Myocarditis via cardiovascular diagnostic testing.

Results

Representing 13 universities, cardiovascular testing was performed in 1597 athletes (964 men [60.4%]). Thirty-seven (including 27 men) were diagnosed with COVID-19 myocarditis (overall 2.3%; range per program, 0%-7.6%); 9 had clinical myocarditis and 28 had subclinical myocarditis. If cardiac testing was based on cardiac symptoms alone, only 5 athletes would have been detected (detected prevalence, 0.31%). Cardiac magnetic resonance imaging for all athletes yielded a 7.4-fold increase in detection of myocarditis (clinical and subclinical). Follow-up CMR imaging performed in 27 (73.0%) demonstrated resolution of T2 elevation in all (100%) and late gadolinium enhancement in 11 (40.7%).

Conclusions and Relevance

In this cohort study of 1597 US competitive athletes with CMR screening after COVID-19 infection, 37 athletes (2.3%) were diagnosed with clinical and subclinical myocarditis. Variability was observed in prevalence across universities, and testing protocols were closely tied to the detection of myocarditis. Variable ascertainment and unknown implications of CMR findings underscore the need for standardized timing and interpretation of cardiac testing. These unique CMR imaging data provide a more complete understanding of the prevalence of clinical and subclinical myocarditis in college athletes after COVID-19 infection. The role of CMR in routine screening for athletes safe return to play should be explored further.

Arterial stiffness is not acutely modified by consumption of a caffeinated soft drink sweetened with high-fructose corn syrup in young healthy adults

We tested the hypothesis that ingestion of a caffeinated soft drink sweetened with high‐fructose corn syrup acutely increases arterial stiffness. In a randomized counterbalanced, crossover design, fourteen healthy adults (25 ± 3 years, 6 women) reported to the laboratory for two experimental visits where 500 ml of tap water (H₂O) or 500 ml of Mountain Dew® (a caffeinated soft drink sweetened with high‐fructose corn syrup (HFCS)) were consumed. Arterial stiffness (carotid‐to‐femoral pulse wave velocity (cfPWV)), peripheral and central blood pressures were measured pre‐consumption, 30 min post‐consumption, and 120 min post‐consumption. Prior to each measurement period, beat‐to‐beat hemodynamic measures were collected. Changes in heart rate, blood pressure, and cardiac output from pre‐consumption did not differ between trials at any timepoint (p ≥ 0.06). Moreover, changes in peripheral or central blood pressures from pre‐consumption did not differ between trials (p ≥ 0.84). Likewise, changes in cfPWV from pre‐consumption to 30 min post‐consumption (HFCS: 0.2 ± 0.3 m/s, H₂O: 0.0 ± 0.3 m/s, p = 0.34) and 120 min post‐consumption (HFCS: 0.3 ± 0.4 m/s, H₂O: 0.2 ± 0.3 m/s, p = 0.77) did not differ. Changes in aortic augmentation pressure, augmentation index, augmentation index corrected to a heart rate of 75 bpm, and reflection magnitude did not differ between conditions at 30 min post‐ (p ≥ 0.55) or 120 min post‐ (p ≥ 0.18) consumption. In healthy young adults, ingesting 500 ml of a commercially available caffeinated soft drink sweetened with high‐fructose corn syrup does not acutely change indices of arterial stiffness and wave reflection.

Program and patient characteristics for the United States Expanded Access Program to COVID-19 convalescent plasma

BACKGROUND

The United States (US) Expanded Access Program (EAP) to COVID-19 convalescent plasma was initiated in response to the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease-2019 (COVID-19). While randomized clinical trials were in various stages of development and enrollment, there was an urgent need for widespread access to potential therapeutic agents particularly for vulnerable racial and ethnic minority populations who were disproportionately affected by the pandemic. The objective of this study is to report on the demographic, geographic, and chronological access to COVID-19 convalescent plasma in the US via the EAP.

METHODS AND FINDINGS

Mayo Clinic served as the central IRB for all participating facilities and any US physician could participate as local physician-principal investigator. Registration occurred through the EAP central website. Blood banks rapidly developed logistics to provide convalescent plasma to hospitalized patients with COVID-19. Demographic and clinical characteristics of all enrolled patients in the EAP were summarized. Temporal trends in access to COVID-19 convalescent plasma were investigated by comparing daily and weekly changes in EAP enrollment in response to changes in infection rate on a state level. Geographical analyses on access to convalescent plasma included assessing EAP enrollment in all national hospital referral regions as well as assessing enrollment in metropolitan and less populated areas which did not have access to COVID-19 clinical trials.From April 3 to August 23, 2020, 105,717 hospitalized patients with severe or life-threatening COVID-19 were enrolled in the EAP. A majority of patients were older than 60 years of age (57.8%), male (58.4%), and overweight or obese (83.8%). There was substantial inclusion of minorities and underserved populations, including 46.4% of patients with a race other than White, and 37.2% of patients were of Hispanic ethnicity. Severe or life-threatening COVID-19 was present in 61.8% of patients and 18.9% of patients were mechanically ventilated at time of convalescent plasma infusion. Chronologically and geographically, increases in enrollment in the EAP closely followed confirmed infections across all 50 states. Nearly all national hospital referral regions enrolled patients in the EAP, including both in metropolitan and less populated areas.

CONCLUSIONS

The EAP successfully provided widespread access to COVID-19 convalescent plasma in all 50 states, including for underserved racial and ethnic minority populations. The efficient study design of the EAP may serve as an example framework for future efforts when broad access to a treatment is needed in response to a dynamic disease affecting demographic groups and areas historically underrepresented in clinical studies.

Responses of Driver-Athletes to Repeated Driving Stints

PURPOSE

The purpose of this study was to examine and quantify the effect of repeated driving stints on the physiologic, metabolic, and hormonal responses of three professional endurance driver-athletes.

METHODS

Core body temperature, HR, and physiological strain index were recorded during the Rolex 24 Hours of Daytona endurance race using the Equivital Life Monitor system. Blood glucose was monitored continuously during the event using a FreeStyle Libre Pro (Abbott, Alameda, CA). Alpha-amylase and cortisol were sampled immediately before the beginning of a stint and immediately after.

RESULTS

First-stint overall and individual driver-athlete responses were similar to those reported in the literature. Later-stint responses diverged from the literature. Reductions in initial core temperature, absence of increases in HR and physiological strain index, and altered glucose and hormonal responses were each observed in the later stint.

CONCLUSION

The data support previous research showing that motorsports has a measurable physiological, metabolic, and hormonal effect on the driver-athlete. This study also shows that multiple stints elicit responses that deviate from the published literature on single-stint events. This study is also particularly interesting in that it represents one of the first times that longitudinal data have been gathered on endurance racing driver-athletes.

Exercise Performance Is Impaired during the Midluteal Phase of the Menstrual Cycle

PURPOSE

This study aimed to test the hypothesis that aerobic exercise performance is impaired in the midluteal (ML) compared with the midfollicular (MF) phase of the menstrual cycle.

METHODS

Twelve recreationally active eumenorrheic women (25 ± 6 yr) completed exercise sessions during the MF and the ML phases. Each session consisted of an 8-km cycling time trial that was preceded by 10 min of cycling performed at a constant power below and above gas exchange threshold. Heart rate, ventilation, and oxygen uptake were continuously measured. RPE and ratings of fatigue were assessed during the time trial using visual analog scales. Total mood disturbance was calculated from the POMS questionnaire administered before and 20 min postexercise.

RESULTS

Salivary progesterone concentration was 578 ± 515 pg·mL-1 higher in ML compared with MF phase (P < 0.01), whereas estradiol concentration did not differ between phases (167 ± 55 vs 206 ± 120 pg·mL-1, P = 0.31). Total mood disturbance before exercise was greater during the ML phase compared with the MF phase (P < 0.01), but this difference was abolished postexercise (P = 0.14). Mean power output was lower during the ML phase (115 ± 29 vs 125 ± 28 W, P < 0.01), which led to a slower time trial in the ML phase (18.3 ± 2.0 min) compared with the MF phase (17.8 ± 1.7 min, P = 0.03). Ratings of fatigue were greater during the ML phase from 2 to 8 km (P ≤ 0.01), whereas no differences in RPE were observed. Heart rate (P = 0.85), minute ventilation (P = 0.53), and oxygen uptake (P = 0.32) did not differ between phases during the time trial.

CONCLUSION

Aerobic exercise performance is worse in the ML phase compared with the MF phase in recreationally active women, which was accompanied by a more negative mood state preexercise and increased ratings of fatigue.

Outcomes of Operative Management of Insertional Achilles Tendinopathy in the Young vs Elderly

Background:

Insertional Achilles tendinopathy (IAT) is a common cause of chronic posterior heel pain. Surgical intervention reproducibly improves patients’ pain and functional status. We hypothesized that patients older than 60 years would have similar improvements in pain and function and low rates of complications after surgery for IAT when compared to a younger cohort.

Methods:

Retrospective review of adult case series in patients undergoing surgical management of IAT. Patients were stratified into those 60 years and younger and those older than 60 years. Patients with prior or concomitant surgical procedures and revisions were excluded. Visual analog scale (VAS), Short Form–36 Physical Component Summary and Mental Component Summary (SF-36 PCS/MCS) scores, wound infection, and recurrence, defined as a redevelopment of heel pain in the operative extremity within 6 months, were assessed with a minimum follow-up of 12 months. Statistical analysis was performed using linear regression mixed models and χ2 analysis. Thirty-seven patients were enrolled, with 38 operative heels. The younger cohort had an average age of 49.1 (range, 26-60) years. The older group had an average age of 66.8 (range, 61-76) years.

Results:

VAS and SF-36 PCS scores for the entire cohort significantly improved at 6 and 12 months postoperatively ( P < .001). Postoperative SF-36 MCS scores for the cohort significantly improved only at 12 months ( P < .001). No significant differences between the young and elderly were seen with regard to improvements in VAS and SF-36 PCS/MCS at 6 or 12 months postoperatively. Multiple linear regression models showed no significant difference between age groups and VAS score, SF-36 PCS/MCS, or change in pain scores after controlling for comorbidities. No significant difference in overall complication rates was seen between the 2 groups (4.9% vs 29.4%, P = .104). There was 1 recurrence of heel pain in the younger group and 4 recurrences of pain in the older group (23.5%) at 6 months, of which 2 resolved at 1 year. There was 1 case of a superficial wound infection requiring antibiotics in the older cohort (5.9%). No patients required surgical revision.

Conclusion:

Surgical management of IAT in an older population produced similar improvements in clinical results when compared to a younger cohort, with no significant increase in postoperative complications.

Level of Evidence:

Level III, retrospective comparative series.

Comparison between a facemask and mouthpiece on breathing mechanics and gas exchange variables during high-intensity exercise

Gas-collection masks are used as a comfortable alternative to the traditional mouthpiece and noseclip during exercise testing protocols in human performance laboratories. However, these masks may introduce potential problems which could affect metabolic and ventilatory parameters, including gas leaks and added dead space. Therefore, the purpose of this study was to compare breathing mechanics, gas exchange variables and ratings of perceived breathlessness (RPB) during high-intensity exercise between a mouthpiece and face mask. Fourteen men [⩒O₂peak = 55.3 ± 7.3 ml·kg^-1·min^-1] were recruited to perform 6 min of cycle ergometry (Velotron Pro, RacerMate, Inc., Seattle, WA) at a work rate corresponding to 90% of ⩒O₂peak while breathing on either (1) a mouthpiece (Hans Rudolph, KC, KS) with nose clip, or (2) a face mask (7450, Hans Rudolph, KC, KS). The difference in ⩒_E between the mouthpiece (156.8 ± 23.3 L/min) and face mask (153.3 ± 21.8 L/min) was not significant (p = 0.534). Similarly, there were no significant differences in breathing mechanics, gas exchange variables or RPB. These data suggest that the facemask can continue to be used interchangeably with the mouthpiece and may even be a more comfortable alternative during high-intensity exercise.