Abstract
High-dose exercise-induced cardiac outcomes may vary between sexes. However, many studies investigating the cardiovascular effects of high-dose exercise have excluded or under-recruited females. This scoping review aimed to describe the recruitment of females in studies assessing the impact of high-dose exercise on cardiovascular outcomes and describe how this has changed over time. This scoping review followed the protocol outlined by Arksey and O’Malley and is reported as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) guidelines. The OVID and EMBASE databases were searched for studies that assessed the effects of high-dose exercise on cardiovascular outcomes. Both professional and nonprofessional groups were included. The review found 2973 studies, and 250 met the inclusion criteria including cumulatively 17,548,843 subjects. Over half the studies (n = 127) excluded females entirely, and only 8 (3.2%) studies recruited all-female participants. The overall mean percentage of females recruited was 18.2%. The mean percentage was 14.5% in studies conducted before 2011 and 21.8% in studies conducted after 2011. Females are an underrepresented group in studies assessing the cardiovascular outcomes related to high-dose exercise. As cardiovascular outcomes vary between sexes, translating findings from a largely male-based evidence may not be appropriate. Future investigators should aim to establish and overcome barriers to female recruitment.
Highlights
Exercise is an umbrella term that can be used to describe a variety of physical activity participation
There is early evidence of a higher prevalence of coronary artery calcification (CAC) in endurance athletes when compared with non-athletic individuals and this may be related to total exercise dose [10]
Regional and Outcome Trends Running is the most commonly studied exercise type and makes up a large proportion of the studies in this literature base (43.3%, Table 3). This analysis provides some early evidence that female recruitment may vary between each exercise type
Summary
Exercise is an umbrella term that can be used to describe a variety of physical activity participation. The wide range of exercise types makes classification and dosing difficult, but this is clinically accomplished by utilising the Frequency, Intensity, Time and Type (FITT) principle [1]. This approach can loosely divide participants into low, middle and high doses. Ventricular and atrial dilatation and increased muscle thickness [5]. While these changes are well described in the scientific literature, the prognostic implications and hard cardiovascular end points are less well known. The strongest evidence for adverse clinical outcomes as a result of high-dose exercise is the increased risk of developing cardiac arrhythmias in later life [6–8]. As argued by Baggish, fibrosis in athletes may portray a “two-hit process” where myocardial injury by infection and subclinical myocarditis is aggravated by endurance exercise leading to more lasting changes such as fibrosis [15]
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