Increased Incidence of Injury Among Runners With COVID-19

Abstract

Background:

Coronavirus disease 2019 (COVID-19) affects multiple organ systems. Whether and how COVID-19 affects the musculoskeletal system remains unknown. We aim to assess the association between COVID-19 and risk of injury.

Hypothesis:

Runners who report having COVID-19 also report a higher incidence of injury.

Study Design:

Cross-sectional study.

Level of Evidence:

Level 4.

Methods:

An electronic survey was distributed from July through September 2020, by New York Road Runners, ASICS North America, race medical directors, and through social media. Inclusion criteria were runners 18 years or older who had participated in ≥1 race (running or triathlon) in 2019.

Results:

A total of 1947 runners participated and met inclusion criteria. Average age was 45.0 (SD, 12.2) years and 56.5% were women. A total of 123 (6.3%) runners self-reported having COVID-19; 100 (81%) reported their diagnosis was from a laboratory test (polymerase chain reaction or antibody) and 23 reported being diagnosed by a medical professional without confirmatory laboratory testing. Since March 2020, 427 (21.9%) reported an injury that prevented running for at least 1 week, including 38 of 123 (30.9%) who self-reported having COVID-19 and 389 of 1435 (21.3%) who did not report having COVID-19 (P = 0.01). After adjusting for age, sex, the number of races in 2019, and running patterns before March 2020, runners who self-reported a diagnosis of COVID-19 had a higher incidence of injury compared with those who did not (odds ratio, 1.66; 95% CI, 1.11-2.48; P = 0.01).

Conclusion:

Injuries were more often self-reported by runners with laboratory-confirmed or clinically diagnosed COVID-19 compared with those who did not report COVID-19. Given the limitations of the study, any direct role of COVID-19 in the pathophysiology of injuries among runners remains unclear.

Clinical Relevance:

Direct and indirect musculoskeletal sequelae of COVID-19 should be further investigated, including the risk of exercise- and sports-related injury after COVID-19.

Coronavirus disease 2019 (COVID-19) was first identified in December 2019 in Wuhan, China, and was declared a pandemic in March 2020 by the World Health Organization. ²⁵ In March 2021, the global number of COVID-19 cases surpassed 120 million people with over 2.6 million deaths worldwide. ³ Although most cases are mild and self-limited, some patients have prolonged symptoms, including fatigue, sleep disturbances, and dyspnea.^8,13 Media reports have described cases of prolonged symptoms after COVID-19 in experienced runners.^2,15

Effects of COVID-19 on the cardiovascular, respiratory, renal, neurologic, psychiatric, and dermatologic systems have been described.^4,9,10 Complications in these organ systems have been attributed in part to direct invasion of the virus via angiotensin converting enzyme 2 (ACE2) receptor mediation leading to a subsequent inflammatory response. ⁴ The data regarding the significance of these effects, like much of the information regarding COVID 19, are constantly evolving, but there has been less focus in the literature on musculoskeletal sequelae. Early data suggest potential musculoskeletal consequences like that of SARS-CoV-1 outbreaks in the early 2000s; direct effects of COVID-19 are possible in the musculoskeletal cell lines with the same ACE 2 receptors. ⁶

For runners and other active individuals, becoming ill with COVID-19 disrupts regular exercise and training. For athletes with mild symptoms, guidelines recommend not training while symptomatic as well as for a period afterward depending on the presence and duration of symptoms.^17,19,24 Short-term reductions of activity have been shown to have negative health consequences,^5,18 which could be similarly seen in inactivity associated with COVID-19. Interruptions of exercise of 7 days or more can also result in muscle disuse atrophy.^5,16 Strength deficits have been associated with an increased risk of musculoskeletal injury, including anterior cruciate ligament injuries in soccer players and iliotibial band syndrome in runners.^20,21 The term “underuse injury” was coined to explain the risk of injury from undertraining or inactivity as compared with the more widely recognized concept of overuse injury. ²³

The purpose of this study is to compare the reported incidence of injury between runners who self-report having had COVID-19 with those who did not. Further delineation of the broader effects of COVID-19 may also allow for improved treatment options and long-term counseling and care for these patients.

Methods

The study was approved by the institutional review board at Hospital for Special Surgery. Data were collected and managed using REDCap electronic data capture tools hosted at Weill Cornell Medicine Clinical & Translational Science Center.^11,12 The survey was administered between July 15, 2020, and September 1, 2020, and was distributed by New York Road Runners, ASICS North America, race medical directors, and through social media. Inclusion criteria included runners 18 years or older who had participated in ≥1 race (running or triathlon) in 2019. Respondents were excluded if they had incomplete responses to questions about COVID-19 diagnosis and injury occurrence. The following questions were used to designate a runner as having a self-reported COVID-19 diagnosis:

1. Have you been told by a health care provider that you have or have had COVID-19? (Included if answered “Yes.”)

2. Have you been tested for an active COVID-19 infection, for example, a viral test, a nasal or saliva swab (polymerase chain reaction [PCR] test)? (Included if answered “Yes—tested positive at least once.”)

3. Have you been tested for COVID-19 antibodies (blood test)? (Included if answered “Yes—tested positive [have antibodies].”)

For runners with a PCR-confirmed COVID-19 diagnosis, additional questions were asked regarding symptom severity, complications, medical clearance for return to running, screening with a resting electrocardiogram, and new symptoms when returning to running.

For self-report of injury, runners were asked if they had experienced an injury since March 2020 that prevented running for at least 1 week. Among those reporting an injury, location of injury and diagnosis (if known) were self-reported. Injuries were then categorized into the following types: bone, joint, muscle/tendon/fascia, nerve, other, and “don’t know.”

Statistical Analysis

Standard descriptive statistics for continuous and categorical variables (eg, frequencies and proportions, means and standard deviations, and medians and interquartile ranges [IQRs]) were used to summarize demographics, races completed in 2019, running patterns before March 2020, self-reported COVID-19 diagnosis, and self-report of injury. Independent-samples Student t tests and chi-square tests were used to compare demographics, races completed, running patterns (ie, average miles run per week and average days of running per week), and current residence between runners with and without a self-reported history of COVID-19 for continuous and categorical variables, respectively. Logistic regression was used to explore the association between injury occurrence and COVID-19 diagnosis, both in univariable analysis and multivariable analysis controlling for age, sex, races completed, and running patterns. Odds ratios (ORs) and 95% CIs were reported. A chi-square test was also used to compare the distribution of injury types between runners with and without a history of COVID-19. Microsoft Excel (Microsoft Corporation) was used for descriptive statistics. JASP (Version 0.14.1) was used for statistical tests and regression analyses.

Results

A total of 2278 runners participated in the study; 1947 (85%) met inclusion criteria and were included in further analysis. Mean age was 45.0 (SD, 12.2) years, 1090 of 1929 (56.5%) were women, and the median number of races completed in 2019 was 6 (IQR: 3, 10).

COVID-19 Diagnosis

There were 123 (6.3%) runners who self-reported a COVID-19 diagnosis that was confirmed by laboratory results or a health care provider. The majority (100 of 123; 81.3%) reported that their COVID-19 diagnosis was from laboratory testing: 59 by antibody alone, 24 by PCR alone, and 17 by both PCR and antibody. In univariate analyses, no significant associations with age, sex, number of races completed in 2019, or running patterns before March 2020, along with self-reported COVID-19 were identified (Table 1). However, runners from New York State had a higher rate of self-reported COVID-19 compared with those from outside New York State, 72 of 765 (9.4%) versus 43/1060 (4.1%), respectively (P < 0.001).

Table 1.

Demographics and running patterns of runners with and without COVID-19

	Not Diagnosed With COVID-19 (n = 1824)	Diagnosed With COVID-19 (n = 123)	P
Age, y, mean (SD)	45.1 (12.2)	43.8 (11.4)	0.24
Sex, count (%)			0.51
Female (n = 1090)	1017 (55.8)	73 (59.4)
Male (n = 839)	789 (43.3)	50 (40.7)
Missing a (n = 18)	18	0
Races completed in 2019, median [IQR]	6 [3, 7]	5 [3, 6]	0.28
Days per week running before March 2020, median [IQR]	4 [3, 5]	4 [3, 5]	0.48
Miles per week running before March 2020, median [IQR]	21 [15, 35]	20 [14.5, 35]	0.47
Current residence, count (%)			<0.001
New York State (n = 765)	693 (90.6)	72 (9.4)
Outside New York State (n = 1060)	1017 (95.9)	43 (4.1)
Missing a (n = 122)	114 (93.4)	8 (6.6)

^aExcluded from chi-square test. IQR, interquartile range.

Association With Injury

More than one-fifth of runners (427/1947; 21.9%) reported an injury since March 2020 that prevented running for at least 1 week. This included 38 of 123 (30.9%) runners who self-reported having COVID-19 and 389 of 1435 (21.3%) without a self-reported diagnosis of COVID-19 (OR, 1.65; 95% CI, 1.12-2.46; P = 0.01) (Table 2). Controlling for age, sex, the number of races in 2019, and running patterns before March 2020, runners who had laboratory-confirmed or clinically diagnosed COVID-19 still had a higher incidence of injury compared with those who did not have COVID-19 (OR, 1.66; 95% CI, 1.11-2.48;P = 0.01).

Table 2.

Association of injury with demographics, running patterns, and self-reported COVID-19 ^a

	Injury (n = 427)	No Injury (n = 1520)	Univariable OR (95% CI)	Multivariable OR (95% CI)
Age, y, mean (SD)	44.7 (12.4)	44.8 (12.0)	1.00 (0.99-1.01)	1.00 (0.99-1.01)
Sex, count (%)
Female (n = 1090)	233 (21.4)	857 (78.6)	Reference	Reference
Male (n = 839)	190 (22.6)	649 (77.4)	1.08 (0.87-1.34)	1.03 (0.82-1.29)
Missing (n = 18)	4 (15.4)	14 (84.6)
Races completed in 2019, median [IQR]	5 [3, 10]	6 [3, 10]	0.99 (0.97-1,01)	0.98 (0.96-1.01)
Days per week running before March 2020, median [IQR]	4 [3, 5]	4 [3, 5]	1.09 (1.01-1.16)*	1.06 (0.96-1.17)
Miles per week running before March 2020, median [IQR]	25 [15, 35]	20 [15, 32]	1.01 (1.00-1.02)**	1.01 (1.00-1.02)
Diagnosed with COVID-19, count (%)
No (n = 1824)	389 (21.3)	1435 (78.7)	Reference	Reference
Yes (n = 123)	38 (30.9)	85 (69.1)	1.65 (1.12-2.46)*	1.66 (1.11-2.48)*

^aMultivariable regression included only patients without any missing independent variables (n = 1923). IQR, interquartile range; OR, odds ratio.

^*P < 0.05; **P < 0.01.

Injury Types Among Runners With/Without COVID-19

The distribution of injury types is listed in Table 3. No significant difference was identified in the distribution of injury type between runners with and without a self-reported history of COVID-19 (P = 0.59).

Table 3.

Distribution of injuries among injured runners with and without self-reported COVID-19 ^a

	Not Diagnosed With COVID-19 (n = 389), n (%)	Diagnosed With COVID-19 (n = 38), n (%)
Bone	36 (9.3)	1 (2.6)
Joint	40 (10.3)	4 (10.5)
Muscle/tendon/fascia	149 (38.3)	13 (34.2)
Nerve	16 (4.1)	3 (7.9)
Other	99 (25.5)	12 (31.6)
Reported that diagnosis is unknown	49 (12.6)	5 (13.2)

^aChi-square test P = 0.59.

Return to Running After COVID-19

Of the 41 runners who were diagnosed by PCR, 7 (17.1%) reported no symptoms, 17 (41.5%) reported mild symptoms, 16 (39.0%) reported moderate symptoms, and 1 (2.4%) reported severe symptoms that required hospitalization but not intubation. Eight (19.5%) consulted with a health care provider for clearance before returning to running and 2 (4.5%) had an electrocardiogram. The following new symptoms were reported on returning to running after recovering from COVID-19: shortness of breath (15; 36.6%), palpitations (4; 9.8%), and chest pain (1; 2.4%).

Discussion

This cross-sectional study of runners showed a significant association between self-reported diagnosis of COVID-19 and injury. Despite the limitations of the study design, this finding deserves further investigation of the role of COVID-19 in the pathophysiology of injury.

There are potential direct and indirect mechanisms through which COVID-19 may increase the risk of injury among runners. In terms of direct mechanisms, myalgias, arthralgias, weakness, and fatigue are attributed to systemic inflammation. ⁶ While myalgias are commonly experienced by patients with COVID-19, they are generally self-limited.^9,22 Rhabdomyolysis and critical illness myopathy have been reported in hospitalized COVID-19 patients.^1,14 In our study, only 1 runner reported being hospitalized but did not report an injury. If the direct effect of systemic inflammation on skeletal muscles predisposed runners to injury, a higher proportion of myotendinous injuries (compared with bone or joint injuries) may have been reported in those with a self-reported diagnosis of COVID-19. However, myotendinous injuries were not disproportionally more frequent among runners with a self-reported diagnosis of COVID-19 (Table 3).

A potential indirect mechanism of injury associated with COVID-19 is the effect of deconditioning and interruption in training while symptomatic. Higher chronic training loads have been suggested as being protective against injury. ⁷ An illness such as COVID-19 would be expected to result in a decreased chronic training load over the months after an illness. Runners may also develop weakness or decreased neuromuscular control because of the time away from training while sick, which could predispose the runner to injury.

This study has several major limitations that must be considered when interpreting the results. As a cross-sectional study, the timing of illness and injury could not be confirmed, and therefore some injuries may have occurred before being diagnosed with COVID-19. However, 59% of runners who self-reported a diagnosis of COVID-19 were from the state of New York. From March through September 2020 (when the survey closed), the majority of cases of COVID-19 in New York occurred in March and April, thereby increasing the likelihood that for many runners, injuries occurred after experiencing COVID-19. ³ Additionally, since this study depended on self-reported data for COVID-19 diagnosis, there may be runners who incorrectly reported their COVID-19 status. Early in the pandemic, testing was limited in the United States so many people with mild symptoms did not get tested. For this reason, clinical diagnosis of COVID-19 (ie, from a medical professional but not necessarily based on a test) was included, even though this also could be inaccurate. Other runners who had COVID-19 may not have sought medical care if they had mild symptoms; they would have not been tested nor clinically diagnosed. Laboratory testing for COVID-19 (whether by PCR, antigen, or antibody) is imperfect, and therefore the false-positive and false-negative results from these could have influenced our results as well. Runners who had COVID-19 may have been more likely to respond to the survey, but this would not have affected the primary outcome of rate of self-reported injury. Furthermore, runners who had COVID-19 may have been more likely to report an injury. There were also insufficient cases of COVID-19 to determine if illness severity could be correlated with injury incidence.

Conclusion

In this large cohort of runners, injuries were more often reported by those who also reported having laboratory-confirmed or clinically diagnosed COVID-19, even after controlling for age, sex, and running history. There was no discernable difference in the types of injuries reported between those with and without a self-reported history of COVID-19. This study cannot differentiate if injuries were directly related to COVID-19, were indirectly related to the interruption in training during the illness, or happened before COVID-19. The findings of this study justify further investigation of injuries among runners and other athletes after COVID-19 to better understand the potential musculoskeletal sequelae of this disease.