The impact of a 21-day ultra-endurance ride on the heart in young, adult and older adult recreational cyclists

Highlights

• Recreational cyclists had a six-fold increase in cardiac arrhythmias after MADRIDE.

• Increases were recorded in both ventricular and supraventricular arrhythmias.

• Arrhythmia rates in adult and older adults were elevated by at least 10-fold.

• Participants aged <18 years experienced reduced arrhythmia incidence.

• Arrhythmia incidence rates were increased without change in autonomic function.

Abstract

Background

This study assessed the acute effect of 21 days of challenging exercise on heart structure and function in recreationally active people across a range of age categories.

Methods

15 recreationally active people completed a 21-day fundraising cycling ride (MADRIDE) over a distance of 3515 km. Twenty-four hour Holter electrocardiography and blood biochemistry analyses were performed before and after the MADRIDE.

Results

Incidence of cardiac arrhythmia was higher after MADRIDE (OR: 5.93; 95% CI: 5.68–6.19), with increases in both ventricular arrhythmias (OR: 9.90; 95% CI: 9.27–10.57) and supraventricular arrhythmias (OR: 3.09; 95% CI: 2.91–3.29). Adults (OR: 11.45; 95% CI: 7.41–17.69) and older adults (OR: 10.42 95% CI 9.83–11.05) were approximately 10 times more likely to experience arrhythmias after the MADRIDE. Whereas, young participants experienced 18% less cardiac arrhythmias after MADRIDE (OR: 0.82; 95% CI: 0.75–0.90). Aortic valve max velocity was reduced (MD: −0.12 m/s; 95% CI: −0.19–0.05 m/s) and mitral valve deceleration time was slower (MD: −28.91 m/s; 95% CI: −50.97–6.84 m/s) after MADRIDE. Other structural and functional characteristics along with heart rate variability were not different after MADRIDE.

Conclusions

Multi-day challenging exercise increased the incidence of both supraventricular and ventricular arrhythmias in active adults and older adults. Increases in arrhythmia rates after MADRIDE occurred without changes in cardiac structure and autonomic control. Further exploration is necessary to identify the causes of exercise-induced cardiac arrhythmia in adult and older adults.

Introduction

Exercise training promotes positive changes to the cardiovascular, musculoskeletal and metabolic systems, and collectively the benefits are indisputable across all ages [1,2]. Additional health benefits are seen with increasing exercise dose [3], such as regular endurance exercise training. Cycling is a popular form of endurance exercise that is experiencing growth in participation rates around the world [4]. Accordingly, participation in ultra-endurance cycling events (i.e., events that exceed 6 h [5]) has increased in individuals across the lifespan [[6], [7], [8], [9]]. Examples include ‘Bicycle Illinois’, where participants cycle 137 km per day for six days [10] and the ‘Great Victorian Bike Ride’, where participants cycle between 50 and 100 km per day for up to nine days [11]. These events are open to participants of all ages, including children, and completing these events has become a personal goal for many entrants [9].

The chronic effects of cycling on the heart of professional athletes have been well documented [[12], [13], [14], [15], [16]]. In addition, the acute effects of multi-day ultra-endurance events, such as the Tour de France, have also been investigated [e.g., 17]. These effects are typically described under the umbrella term ‘athlete's heart’ [18] and include beneficial cardiac adaptations that occur as a result of chronic exercise training, such as bradyarrhythmia and cardiac enlargement, but with no signs of cardiovascular disease [19]. Further, athletes have a lower sudden cardiac death risk (e.g., only one sudden cardiac death has occurred during the Tour de France, an incidence rate of 0.007/100,000 participant years [20]). Regardless, cyclists are at elevated risk of adverse cardiovascular disease events [21] and sudden cardiac death is still reported in both professional [20] and recreational [[22], [23], [24]] cyclists. Although rare [26], sudden cardiac death has occurred in ultra-endurance cycling events around the world, and the real incidence is likely to be underestimated [25]. For example, a 23-year old professional cyclist died after suffering a double cardiac arrest in the ‘Carpathian Couriers Race’ [20], and fatalities attributed to myocardial infarction occurred during an endurance event in London (RideLondon) in 2014, 2016 and 2017, where these recreational cyclists were 36, 48 and 67 years of age, respectively.

Little is known about the acute effect of ultra-endurance exercise on the heart in the general population who exercise recreationally. Existing data are limited to one cohort study that included before and after measurements on a group of 20 cardiologists aged 32 to 54 years who completed an eight day cycle covering 1580 km [27]. These authors reported no clinically important functional or biochemical changes to the heart [27]. Although reassuring, transthoracic echocardiograms were only obtained for seven adult cyclists, the volume of exercise was modest when compared to most ultra-endurance events, and the cyclists obtained professional cycling advice several months prior to the ride. In contrast, it is likely that many participants in public multi-day endurance events are of a broad age range and have a varied exercise training background with no specialist advice; consequently, such participants might be exposed to an increased risk of major cardiovascular disease events.

Considering that participation in challenging multi-day ultra-endurance events is increasing across the lifespan, there is a need to assess the acute effects of such events on the heart of non-athletic populations. Therefore, the aim of this study was to assess the acute effects of 21 days of challenging exercise on cardiovascular structure and function in recreationally active people across a range of age categories.