Potential acute effects, as well as the effects during recovery from acute human rhinovirus infection (HRVinf) on sport and exercise performance parameters in athletes

Recreational and professional athletes increase training load to achieve the desired training adaptations for competitive events. Any interruption in training due to unforeseen events, such as injury or illness, may undermine the individual's ability to reach or maintain the necessary level of sports performance at an intended time. An acute illness event can be broadly defined as any set of symptoms, not linked to a physical injury, that may cause interruption or modification of an individual’s normal training regime for at least two days and requires medical intervention ^1-4. Acute illness is a potential factor that can lead to interruption in training for physically active individuals and competitive athletes, and this presents challenges to stay consistent at training and maintain sports performance, particularly at competition times. An acute illness can affect many organ systems in the body, including the cardiovascular, respiratory, gastrointestinal, renal, neurological, musculoskeletal, and integumentary organ systems ^5-10. It is well documented the respiratory system is the most frequent organ system affected by acute illness in the athletic and physically active population. Specifically, acute respiratory illness (ARill) is the most common acute illness seen in the athletic population ^11-13. An ARill can be categorised by pathology, where the illness may be non-infectious or infectious, namely acute respiratory infection (ARinf) ¹⁴. Therefore, ARinf is the most common acute illness amongst physically active individuals and athletes ^4,13,15-16.

An acute respiratory infection (ARinf) can be classified by anatomical location, as: 1) upper respiratory tract infection, above and including the larynx (nose, sinuses, 1pharynx, larynx), and is associated with symptoms such as a blocked or runny nose, sore throat and swollen glands ^12,15,17-18, or 2) a lower respiratory tract infection, below the level of the larynx (trachea, bronchi, lungs or pleura), and is associated with symptoms such as shortness of breath, coughing, wheezing, and chest pain ^15,17. An ARinf can be caused by many pathogens, most frequently viruses ¹⁹. Data from several studies indicate that >80% of ARinf in athletes are caused by viruses ¹⁹, mostly by the Human Rhinovirus (HRV) ^20-24. Therefore, Human Rhinovirus Infection (HRVinf) is the most common ARinf in physically active individuals ^20-24. Acute illness, and specifically ARinf, may impact the individual’s ability to perform at an optimal level when returning to exercise ²⁵. Therefore, the potential acute effects, as well as the effects during recovery from acute human rhinovirus infection HRVinf on sport and exercise performance parameters in athletes, are important and are the focus of this thesis.

It is important to understand the difference between sports performance and exercise performance. Sports performance refers to highly variable demands during different formats of exercise that require skill, intense and structured training and are competitive ^26-27. Exercise performance, on the other hand, is an umbrella term that describes the result of a physiological response by the body to an acute bout of exercise or to multiple bouts of exercise over time ²⁸. There are multiple components of exercise performance, including cardiorespiratory endurance, flexibility, muscle function (muscle strength, power, and endurance), and neuromuscular control ^27,29. Muscle function parameters of exercise performance are defined by the function of a group of muscle fibres and include muscle strength, muscle endurance, and muscle power 30. Neuromuscular control includes measures of motor skills such as balance, coordination, proprioception, and postural stability ^30-31. The effects of ARinf on exercise and sports performance have recently been reviewed in an international Olympic committee consensus.²⁸ A main message from this review is that there are very limited data on the effects of ARinf on exercise and sports performance. There are some data on the effects of ARinf on the cardiopulmonary function during exercise, but the effects of ARinf on musculoskeletal function are not well documented. Specifically, the effects of ARinf on muscle function (muscle strength, endurance, and power) and neuromuscular control, which may impact the individual's performance and recovery following an ARinf is not documented. The time course of muscle function and neuromuscular control after recovery from ARinf is also not reported. This information is important for physically active individuals, coaches, and health professionals, as premature return to training can aggravate symptoms or lead to adverse medical outcomes, whereas extended recovery may inhibit exercise performance.