Risk Factors for Collegiate Swimmers Hospitalized With Exertional Rhabdomyolysis

Epidemiology of Exertional Rhabdomyolysis in the United States: Analysis of NEISS Database 2000 to 2019

OBJECTIVE

There have been numerous case series of exertional rhabdomyolysis (ER) but no comprehensive studies investigating the incidence of ER in the civilian athletic population in the United States (US).

METHODS

A retrospective review of patients with ER presenting to emergency departments in the US over a 20-year period between 2000 and 2019 was performed using the National Electronic Injury Surveillance System (NEISS) database.

RESULTS

The national estimate of hospital visits in the US for ER during the 20-year period was 40,654 (0.66 per 100,000 population). There was a 10-fold increase in the incidence of ER from the first to the second decade. The odds of ER were 3.77 (95% CI 3.67-3.86, P < .0001) times higher for males (31,921, 78.5%, 1.06 per 100,000) than females (8,733, 21.5%, 0.28 per 100,000) and 3.82 (95% CI 3.71-3.93, P < .0001) higher in African Americans (33.6, 0.93 per 100,000) than white patients (53%, 0.24 per 100,000). American football (3,064, 7.5%) was responsible for 43.9% of the sports-induced ER cases. The majority (67.3%) of ER cases occurred between the ages of 16 and 35 years old. The majority of patients required hospitalization (26,550, 65.3%).

CONCLUSIONS

The number of ER cases presenting to emergency departments in the US increased from 2000-2009 to 2010-2019. Young males and African Americans are at highest risk of ER. There was a high rate of hospitalization.

Pandemic-Induced Reductions on Swim Training Volume and Performance in Collegiate Swimmers

The COVID-19 pandemic caused significant training disruptions during the 2020-2021 season, due to lockdowns, quarantines, and strict adherence to the pandemic protocols. The main purpose of this study was to determine how the pandemic training restrictions affected training volume and performance in one collegiate swim team. Cumulative training volume data across a 28-week season were compared between a pandemic (2020-2021) versus non-pandemic (2019-2020) season. The swimmers were categorized into three groups (sprinters, mid-distance, and long-distance) based on their training group. The performance times of 25 swimmers who competed in the regional championships, during both the non-pandemic and pandemic year, were compared via one-way ANOVA. Twenty-six male and 22 female swimmers commenced the 2020-2021 (pandemic) season, with 23% of the swimmers voluntarily opting out. Three COVID-19 cases were confirmed (2%) by the medical staff, with no long-term effects. Significant reductions in the average swim volume were verified in sprinters (32,867 ± 10,135 vs. 14,800 ± 7995 yards; p < 0.001), mid-distance (26,457 ± 10,692 vs. 17,054 ± 9.923 yards; p < 0.001), and long-distance (37,600 ± 14,430 vs. 22,254 ± 14,418 yards; p < 0.001) swimmers (non-pandemic vs. pandemic season, respectively). In the regional performance analyses, the sprinters swam faster (n = 8; -0.5 ± 0.6 s), while the mid-distance (n = 10; 0.17 ± 2.1 s) and long-distance (n = 7; 6.0 ± 4.9 s) swimmers swam slower (F = 11.76; p = 0.0003; r² = 0.52). Thus, the pandemic caused significant reductions in swim training volume, with sprinters performing better and long-distance swimmers performing worse at the regional championships.

Paradoxical Relationships between Serum 25(OH)D and Ferritin with Body Composition and Burnout: Variation by Sex and Sports Team

Adequate serum vitamin D and iron levels are thought to influence physical training adaptations and mood positively. The primary purpose of this prospective, observational study was to investigate relationships between serum 25-OH vitamin D/25(OH)D and serum ferritin levels with body composition and athlete burnout symptoms. Seventy-three collegiate athletes (female: n = 49; male: n = 24) from indoor (swimming, basketball) and outdoor (soccer, cross-country) sports were tested pre-season and post-season for serum 25(OH)D and serum ferritin (nutrient biomarkers) via venipuncture; body composition (total lean mass, bone mineral density/BMD, and % body fat) via dual energy X-ray absorptiometry (DXA) scans; and athlete burnout symptoms (post-season) via the athlete burnout questionnaire (ABQ). When male and female cohorts were combined, significant correlations (Pearson’s r) were noted between pre-season serum 25(OH)D versus the change (∆: post-season minus pre-season) in both BMD (r = −0.34; p = 0.0003) and % body fat (r = −0.28; p = 0.015). Serum ferritin ∆ was significantly associated with lean mass ∆ (r = −0.34; p = 0.003). For burnout symptoms, serum 25(OH)D ∆ significantly explained 20.6% of the variance for devaluation of the sport in the male cohort only. Across time, serum 25(OH)D levels decreased while serum ferritin levels increased, non-significantly, in both males and females. Relationships between nutrient biomarkers and body composition were opposite of physiological expectations.

Muscle Damage, Soreness, and Stress During Preseason Training in Collegiate Swimmers

BACKGROUND

In 2014, 6 collegiate swimmers were hospitalized for symptomatic exertional rhabdomyolysis.

OBJECTIVE

To serially monitor and assess relationships between skeletal muscle membrane disruption, upper body soreness (UBS) and lower body soreness (LBS), and stress during the first 6 weeks (timepoints) of preseason training in collegiate male and female swimmers.

DESIGN

Prospective observational study.

SETTING

College/university.

PARTICIPANTS

Forty swimmers.

INDEPENDENT VARIABLES

Upper and lower body soreness rating (0-10); testosterone (T), cortisol (C), and T/C ratio.

MAIN OUTCOME MEASURES

Creatine kinase (CK) and myoglobin (over time) versus independent variables.

RESULTS

Weekly training load consisted of ∼87% swimming, ∼5% running, and ∼8% weight training, which increased from 15.8 hours to 20.5 total training hours per week over the first 6 weeks of training. Muscle damage in collegiate swimmers was modest and peaked after the first week of training (week 2) for men (CK = 438 ± 259 U/L; P < 0.0001; r2 = 0.28; myoglobin = 47 ± 18 ng/mL; P = 0.001; r2 = 0.22) and women (CK = 446 ± 723 U/L; P < 0.01; r2 = 0.13; myoglobin = 63 ± 140 ng/mL, not significant) with high variability. Data were presented as peak mean ± SD, significant P value, and r2 from repeated-measures analysis of variance. A temporal disconnect was noted between muscle damage and UBS, which peaked at week 5 in both men (5 ± 2; P < 0.0001; r2 = 0.44) and women (6 ± 2; P < 0.0001; r2 = 0.57). The serum cortisol level decreased over time, which peaked at week 1 (baseline) in men (15 ± 6 μg/dL; P = 0.0004; r2 = 0.38) and women (19 ± 10 μg/dL; P < 0.0001; r2 = 0.49). The testosterone level remained unchanged, which promoted an anabolic hormonal environment that peaked at week 6 (increasing T/C ratio) in men (58 ± 32; P = 0.0003; r2 = 0.31) and women (4 ± 3; P = 0.04; r2 = 0.18) despite gradual increases in training and soreness.

CONCLUSIONS

Muscle soreness does not parallel muscle membrane disruption. A 1-week "transition" period is required for muscles to adapt to intense/novel training.

Resting Blood Pressure in Collegiate Swimmers During a Competitive Season: A Prospective Observational Study

Introduction The purpose of this study was to describe and examine differences in resting blood pressure (BP) during an eight-week time frame in the course of the competitive season among collegiate swimmers of varied sexes. Methods A prospective observational study using a sample of convenience of National Collegiate Athletic Association (NCAA) Division 1 female and male swimmers from one university were invited to participate. Blood pressure was measured using standardized methodology at six encounters spaced over eight weeks. Descriptive statistics analyzed demographics, mean BP, and BP classifications. A pairwise t-test analyzed differences in the mean BP and BP classification by sex. The Bonferroni correction was applied given the multiple variables included in the analysis with statistical significance determined to be p≤0.002. Results Thirty-eight swimmers (15 males and 23 females) met the inclusion criteria. Differences between sexes were identified with a higher mean diastolic BP observed in males at the third encounter (p=0.0004) and a higher mean systolic BP observed in males at the sixth encounter (p=0.0002). Four males and four females were identified with a BP classified as stage 1 or 2 hypertension at the first encounter; however, six males and no females met this criterion at the last encounter which was statistically significant (p=0.0004). Conclusions Increased BP from baseline measured for systole, diastole, and BP classifications was significant in male compared to female swimmers. Specifically, divergence in BP by sex first appeared in the diastolic measures at three weeks and in the systolic measures and BP classifications by eight weeks.