Although CV health and fitness are known to have a genetic component, most research indicates that at least half of one’s CV health and fitness is determined by lifestyle and environment, and is therefore controllable to a large extent. Exercising to music from external speakers or headsets gained popularity in the 1970s and 1980s as many people actively responded to the positive news about exercise and CV health. They participated in exercise classes and moved to the music of a variety of genres and loudness. Exercise workout tapes evolved into portable MP3 players, providing even more flexibility for exercising while listening to one’s favorite tunes virtually anywhere. In the midst of these popular music workouts that gained a large following in the 1980s, audiologist Richard Navarro warned that listening to loud music while exercising might exacerbate the risk of hearing loss because of the exercise-induced redistribution of blood from the inner ear to the working muscles, leaving organs and tissues in the inner ear vulnerable to low oxygen levels.4 His hypothesis initiated experiments, a few supporting the notion that any type of stress that increased heart rate dramatically (such as exercise), regardless of whether it included noise, contributed to temporary hearing loss. One of the first studies to investigate the association between hearing sensitivity and exercise found that when an acute bout of exercise was accompanied by noise exposure, a greater amount of temporary hearing loss occurred (compared against a resting state while in the presence of noise).5 The conclusion that one exercise session accompanied by noise resulted in hearing loss was not supported by follow-up experiments.

    The first published study that investigated regular exercise and hearing acuity was conducted in 19736 and reported improved hearing in subjects who participated in an unstructured exercise program for 20 weeks. Given these conflicting results, we challenged Navarro’s theory as well as the few studies that appeared to support his work. When we conducted experiments that carefully controlled for exercise intensity, fitness level and specific noise exposure for a set time, our laboratory could not replicate his early results. In fact, we found that one bout of exercise alone did not alter hearing. Only when subjects were exposed to high-level noise, regardless whether they were sitting or exercising, were changes in hearing observed. Furthermore, like Ishmail’s study, we found that persons who exercised regularly had better hearing than those who were sedentary.

    Over the past 30 years, it has become clear that CV health and fitness positively impact hearing. Results from different laboratories across the country have shown that compared to low-fit individuals, persons with high CV health and fitness, particularly after age 50, maintain better hearing well into old age.6-11 As researchers began to understand the role of sensory receptors in the nerve responsible for hearing, the relationship between the CV system and hearing ability became an increasingly popular topic. Exercise is positively correlated with improved blood circulation, prevention of neurotransmitter loss and less noise-induced hearing loss.12 These changes in the vascular system allow improved blood circulation into different parts of the ear including the stria vascularis in the cochlea. This is important because the stria vascularis relies on adequate blood flow to function properly. Without constant replenishment of blood flow to the sensory receptors in the nerve of hearing, hearing ability could be compromised.

    Cardiovascular fitness may also help to preserve the way in which the central nervous system interprets speech (known as central auditory processing: see Chapter Three, Q&A#3). It has been found that CV fitness may reduce neurotransmitter loss associated with aging and thus preserve central auditory processing.12