Effects of Exercise Training on Hearing Ability

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1 Effects of Exercise Training on Hearing Ability Mark Cristell, Kathleen M Hutchinson and Helaine M Alessio Department of Communication and Department of Physical Education, Health and Sport Studies Miami University, Oxford, Ohio, USA Cristell M, Hutchinson K, Alessio H. Effects of exercise training on hearing ability. Scand Audiol 1998;27: This study was designed to determine whether improvements in both cardiovascular fitness and hearing sensitivity occurred following 2 months of aerobic exercise training. Seventeen moderately-low fit ( VO 2 peak 32 ml/kg/min) young adults were evaluated for cardiovascular fitness and pure-tone and temporary threshold shifts (TTS) at 2, 3, and 4 khz before and following 10 min of noise. Subjects exercised for 8 weeks by cycling on a bicycle ergometer at 70% of their peak oxygen consumption ( VO 2 peak). Average VO 2 peak increased 34% (p 0.05) above pre-exercise training levels. Both pure-tone hearing (2 and 3 khz) and TTS improved following 2 months of exercise training at the evaluated frequencies (2, 3, and 4 khz) (p 0.05). Cardiovascular health as indicated by VO 2 peak was associated with hearing sensitivity. Although the mechanisms have not been identified, these results support the existence of a cardiovascular health-hearing synergism. Key words: Audiology, noise-induced hearing loss, physical fitness, temporary threshold shift. Received: February 10, 1997/Accepted April 3, 1998 Address for offprints: Kathleen M. Hutchinson, Miami University, COM Department, Oxford, Ohio 45056, USA (Tel , fax , . Hutchik@muohio.edu) Introduction There is evidence that a healthy cardiovascular system may have a protective role in hearing conservation. Subjects who completed a 20-week-long physical fitness program improved their peak oxygen consumption ( VO 2 peak) as well as baseline hearing thresholds (Ismail et al., 1973). Individuals with relatively high cardiovascular fitness levels ( VO 2 peak 40 ml kg 1 min 1 ) had a decreased susceptibility to temporary threshold shift (TTS) at several frequencies following noise exposure (Manson et al., 1994). Results from our laboratory concur with Ismail et al. (1973) that, compared to lower fit persons, individuals with high cardiovascular fitness have more acute hearing and are less susceptible to TTS. These provocative results have yet to be confirmed in a supervised exercise regimen assessing the relationship between hearing ability and cardiovascular fitness over time. Interestingly, acute cardiovascular responses to exercise in combination with noise do not appear to influence the level of hearing sensitivity (Hutchinson et al., 1991). Yet chronic cardiovascular adaptations to physical training might attenuate the level of hearing loss from noise exposure, thus preserving hearing sensitivity (Manson et al., 1994). The purpose of this study was to compare hearing ability among low to moderately fit persons before and after completing an 8-week aerobic exercise training program. Hearing ability is defined as the amount of a person s hearing sensitivity at several frequencies and also improvement of hearing measured as a reduction of TTS. Although a number of factors contribute to noise susceptibility, our intent was to determine if hearing ability could be enhanced concomitant with improved cardiovascular functioning following 8 weeks of aerobic exercise training. Material and Methods Subjects Subjects were 30 volunteers with a mean age years. Each subject was screened to determine normal hearing ( 25 db HL at octave intervals from 0.25 to 4 khz) on a Beltone 2000 pure-tone audiometer. No one indicated any history of middle-ear disease or previous significant noise exposure. Of the 30 subjects who volunteered and had a VO 2 peak 32 ml kg 1 min 1, 17 completed the entire protocol, 3 dropped out, and 10 served as controls, who met at the same time as the exercise group but did not exercise. All underwent pre- and post-training cardiovascular and hearing tests. Subjects signed informed consent forms approved by the university s Human Subjects Review Board before testing began. Baseline Procedures VO 2 peak was determined using a graded exercise test on a Monark bicycle ergometer. VO 2 peak is similar to VO 2 max,

2 220 M Cristell et al. which is a measure of maximum oxygen consumption following a progressive workload usually performed to volitional exhaustion. VO 2 peak represents a valid and reliable measure of cardiovascular fitness (American College of Sports Medicine, 1986). Subjects began by pedaling at 50 rev min 1 against a 1 kg resistance for 2 min. Thereafter, resistance was increased 0.5 kg every 2 min. Methods for assessing heart rate and oxygen uptake have been described previously (Alessio & Hutchinson, 1991). The VO 2 peak test was considered valid if at least two of the following criteria were satisfied: VO 2 failed to increase 100 ml min 1 despite an increased workload, respiratory exchange ratio 1.0, heart rate was within 20 beats of agepredicted maximum heart rate, and a subject could not continue pedaling at 50 rev min 1. No test had to be terminated due to positive ECG recording, subject report of angina, or any other abnormal exercise response. Once VO 2 peak on a bicycle ergometer was obtained it was then possible to calculate a workload that required 70% of VO 2 peak (American College of Sports Medicine, 1986). Experimental Procedures Following the initial hearing screening and VO 2 peak determination, subjects participated in an experimental condition lasting 30 min. The experimental protocol was set up in the following way. Each subject reported to the laboratory and underwent baseline hearing, heart rate, blood pressure, and core temperature tests. Participants were seated in a double-walled IAC suite having an acoustic environment suitable for threshold measurements (ANSI, 1991). The hearing test was conducted with the Madsen 0B8-22 audiometer calibrated to the ANSI standard (ANSI, 1996). During each hearing test, sweep frequency thresholds were obtained. Subjects were carefully instructed to press a button when they heard the pulsed tone and release it as soon as the sound faded away. Subjects were told not to let the tone grow very strong and never let it stay away too long. Averages of the peaks and valleys of tracing excursions were calculated for 2, 3, and 4 khz from a printout of the monitor recording. Both pure-tone thresholds and TTSs were determined. Heart rate (HR) was measured by a UNIQ model 8799 heart watch, receiver, and transmitter. Blood pressure was measured by a certified physician assistant using a manual sphygmomanometer (PyMaH Corp). Tympanic core temperature was measured using the First Temp thermometer (Intelligent Medical Supplies), whch measures temperature of the external auditory canal proximal to the tympanic membrane and converts this value to core temperature. In the experimental condition, the subjects were seated and TDH-50 earphones were placed over the ears. HR, blood pressure, and core temperature were recorded continuously. A 1/3 octave band-filtered noise with 2 khz center frequency at 104 db SPL was administered to one ear for 10 min after which time the subject s hearing level was tested. For the sweep procedure, the test started at 1 khz 1 min following the noise. The program produced a continuous frequency sweep at 62.5 Hz per 4 sec rate between 1 and 2 khz and increased 62.5 Hz per 2 sec between 2 and 4 khz. Therefore, the post-testing latencies for the sweep frequencies were: 2.06 min for 2 khz; 2.6 min for 3 khz; and 3.14 min for 4 khz. Subjects returned to the clinic24¹48 h following the tests to determine if any changes in pure-tone threshold or TTS persisted. Threshold repeatability measurements for two conditions (baseline and noise) were conducted with 10 subjects. For reliability evaluation, these subjects were tested again in a session separated by at least 1 but no longer than 5 days after the initial testing. Following hearing assessment, the subjects embarked on an 8-week aerobic exercise training program, in which they cycled on a bicycle ergometer at least twice a week for 30 min a day. This exercise protocol was designed to improve cardiovascular fitness by approximately 15¹25%. Exercise HR was assessed to monitor changes in each person s fitness. The force of the cycle s flywheel was increased in order to maintain HR at a level consistent with that at 70% of VO 2 peak. At the end of the 8th week, the participants were administered a VO 2 peak test again to assess any change. Next, a second baseline hearing measurement for pure-tone thresholds was obtained. The noise condition was introduced with the same parameters and subjects were again administered a hearing test following 10 min of noise for TTS measures. Ten subjects in the control group met at the same time as the exercise group. However, instead of exercising, this group sat and received information about health-related benefits of regular exercise and exercise opportunities at local campus and community programs. Pre and post 8-week training protocols were the same for the exercise and control groups. Statistical Analysis Analysis of variance with repeated measures was used to compare the baseline hearing levels and temporary hearing loss that occurred following the noise conditions. Hearing loss values are reported at three frequencies: 2, 3, and 4 khz. Two three-way designs (TTS 3 frequencies training and pure-tone hearing level 3 frequencies training) had repeated measures on each factor. When appropriate, the sphericity assumption was tested using Greenhouse-Geisser analysis. Post-hoc analysis using contrast-comparison tests compared levels of hearing loss between pre- and post-exercise training at each frequency to determine whether improved VO 2 peak is associated with improved pure-tone hearing and/or less hearing loss following the exercise program. The significant probability level was p Results Cardiovascular Findings Table I summarizes characteristics of the subjects including VO 2 peak and peak HR. Mean HR peaks for the 17 subjects in both pre- and post-training occasions were compared. Mean HR peak before the initiation of exercise training was beats min 1. Post-training mean HR peak was beats min 1. This 2% increase in mean HR peak did not reach the p 0.05 level of significance. Nor did mean HR peak for the control group change significantly ( compared to beats min 1 ). This slight change in mean HR peak for both the control and exercise groups on the second exercise test was in the range of experimental error. Seventeen subjects with an initial mean VO 2 peak of ml kg 1 min 1 completed the study. After the 8-week training program, mean VO 2 peak values

3 Exercise training and hearing ability 221 Table I. Characteristics of subjects in the exercise training and non-exercise control groups before initiation of the exercise training intervention Exercise training Control No Age Gender 1 male all female VO 2 peak (ml kg 1 min 1 ) HR peak (beats min 1 ) Resting systolic blood pressure (mmhg) Resting diastolic blood pressure (mmhg) Resting core temperature ( C) increased to ml kg 1 min 1 (F 1;16 ¼ 30:88, p ¼ 0:0001). Figure 1 illustrates the 25.5% increase in VO 2 peak from pre- to post-exercise training. Three subjects of the original 20 volunteers did not adhere to the exercise training protocol; that is, they missed an average of 6 out of a total of 16 exercise sessions during the 8-week training period. Nevertheless, they completed cardiovascular and hearing tests immediately before and after weeks 1 and 8, respectively. These three subjects showed no change in VO 2 peak (mean VO 2 peak pretraining period ¼ 30:1mlkg 1 min compared to 31.6 ml kg 1 min ). Nor did VO 2 peak of the control group change ( compared to ml kg 1 min 1 ). No other measured cardiovascular variables changed from pre-training levels. Audiometric Measures Two sets of threshold data were obtained for the participants before and following 8 weeks of exercise training as baseline measures and TTS following an experimental condition that included 10 min of noise. Figure 2 shows the pure-tone threshold values at three frequencies before and after 8 weeks of aerobic exercise training. At 2 khz, an ANOVA with repeated measures indicated that pure-tone threshold improved following the training program (F 1;16 ¼ 4:22, p ¼ 0:05); at 3 khz, significant improvement was found (F1; 16 ¼ 7:6, p ¼ 0:01); and at 4 khz the 7% change was not significant (F 1;16 ¼ 0:01, p ¼ 0:9). Although a difference less than 5 db in baseline threshold may not be clinically important, these results point to a consistent trend of threshold improvement across participants. Figure 3 shows TTS values with standard error bars at three frequencies before and after 8 weeks of aerobic exercise training. At 2 khz, pre-exercise training TTS was 7.4 db ( 1.8), while post-exercise training results improved significantly to 2.9 db ( 1.08) (F 1;16 ¼ 5:24, p ¼ 0:036). At 3 khz, pre-training TTS was found to be 9.8 db ( 1.28), while post-training TTS at this frequency was 5.9 db ( 1.1) (F 1;16 ¼ 9:45, p ¼ 0:007). At 4 khz, pre-exercise training TTS was 10.3 db ( 0.8), while post-exercise training TTS was 4.2 db ( 1.06) (F 1;16 ¼ 19:6, p ¼ 0:0004.). At every frequency measured, post-exercise training TTS was significantly less than pre-exercise training TTS, indicating a decreased susceptibility to the effects of noise exposure following exercise training. Individual TTS values before and after the exercise regimen showed substantially reduced values following training at all three test frequencies. This pattern of reduction was consistent for most, but not all, exercise participants. TTS values and VO 2 peak measures were converted to Z scores for calculation of correlation coefficients to standardize the different ranges of each variable. Calculation of these correlation coefficients (Table II) showed that the TTS magnitudes at 2, 3, and Fig. 1. Peak oxygen consumption and standard error bars in the experimental group pre- and post-exercise training (*p 0.05).

4 222 M Cristell et al. Fig. 2. Pure-tone threshold and standard error bars in decibels pre- and post-exercise training; top: experimental group, bottom: control group (*p 0.05) (B Pre-training; A post-training). 4 khz were not significantly correlated with VO 2 peak in this investigation. The correlation at 2 k with posttraining VO 2 peak approached significance (r ¼ 0:54, p ¼ 0:052). TTS values were highly variable among subjects. Correlations between pure-tone hearing threshold and peak oxygen consumption were found to be consistently and inversely related. In some cases, the correlations reached significance (Table III). In a separate analysis, threshold repeatability was assessed by finding the threshold difference between the two test sessions of each subject at each frequency in each condition of quiet and noise. Ten subjects were tested before the exercise regimen in two half-hour sessions, separated by 1, but no longer than 2, weeks. The mean threshold differences were within 0.54 db and the standard deviations ranged from 1.1 to 4.1 across the three test frequencies and the two test sessions in baseline (quiet) comparisons. The mean threshold differences were within 5.1 db and the standard deviations ranged from 4.2 to 16 across three frequencies and the test sessions in noise. The results of ANOVA with repeated measures revealed that the main effects for

5 Exercise training and hearing ability 223 Table III. Pearson correlation coefficients between VO 2 peak and pure-tone hearing threshold levels at three frequencies before and after exercise training Frequency 2 khz 3 khz 4 khz VO 2 peak Before training * 0.42 Post training 0.60* *p.05 (r 0.46). Discussion Fig. 3. Temporary threshold shift and standard error bars in decibels pre- and post-exercise training; top: experimental group, bottom: control group (*p 0.05) (B Pre-training; A posttraining). test session and frequency and all interactions were not significant in the baseline and in the noise condition. Therefore, intrasubject thresholds were found to be repeatable and within a clinically acceptable range for the sample tested, regardless of test session and frequency. Furthermore, no change in TTS occurred in three subjects who did not adhere to the 8-week exercise training. TTS at 2, 3, and 4 khz changed only 2.2, 3.4, and 4.9, respectively, when comparing pre- and post-training in the non-compliers. Table II. Pearson correlation coefficients between VO 2 peak and magnitude of TTS levels at three frequencies before and after exercise training Frequency 2 khz 3 khz 4 khz VO 2 peak Before training Post training Noise exposure has long been recognized as a major cause of hearing loss. There is growing support for developing and implementing intervention programs to protect all persons against the dangers of noise-induced hearing loss (Kirkwood, 1992). This paper describes an intervention program for hearing conservation consisting of regular aerobic exercise designed to enhance cardiovascular fitness and health. In the present study, hearing sensitivity as indicated by pure tone and TTS significantly improved in some of the frequencies measured following 8 weeks of exercise training. Participants also increased their cardiovascular fitness level by 25%. The finding that cardiovascular fitness plays a role in hearing sensitivity is intriguing. Although this is not the first report (Ismail et al., 1973), it is the first controlled study in which pure-tone threshold and TTS are compared before and after an 8-week cardiovascular exercise training regimen at quiet and following noise exposure. Individuals considered to be in a moderately low cardiovascular fitness category ( VO 2 peak 32 ml kg 1 min 1 ) were aerobically trained for 8 weeks and improved their VO 2 peak 25% to a mean of 37 ml kg 1 min 1. Following aerobic exercise training, subjects sustained less temporary hearing loss as indicated by TTS at all frequencies measured in this study. Additionally, mean baseline hearing levels in two frequencies also improved following exercise training. This is the first report we are aware of indicating that baseline hearing can be improved in a relatively short period of time. Subjects in the control group and those who did not adhere to the exercise training protocol did not show improvements in either pure-tone threshold or temporary shift following 8 weeks. Many factors influence the accuracy of clinical audiometric measurements, among which are the differences in tone presentation techniques, patient response patterns, equipment and testing environment. Variations in test results were minimized by adoption of a uniform tone

6 224 M Cristell et al. delivery, instrumentation calibration, and careful, consistent directions to the subjects. Certainly, the use of conventional automatic audiometry in evaluating changes in hearing across several testing times has the disadvantage of learning effects with repetition. However, intrasubject baseline hearing thresholds were found to be reliable using a test versus retest paradigm. Burns & Hinchcliffe (1975) found that the learning factor which occurs between hearing tests accounts for 1¹2dB of improvement in the high frequency range. Consistent improvement in hearing threshold values following 8 weeks of exercise training ranged from 3.9 db to 6.11 db within a group of 17 subjects. Temporary hearing loss occurred before and after exercise training when subjects were exposed to noise. Following the improvement of VO 2 peak, on average, subjects suffered one half the temporary hearing loss compared to pre-training levels. The current findings support the notion that susceptibility to TTS is related to a person s cardiovascular fitness, but other factors also contribute to the degree of TTS. The mechanism relating cardiovascular fitness and hearing sensitivity is not clearly understood. Ismail et al. (1973) suggested that increased activity of key oxidative enzymes associated with cardiovascular fitness may be partly responsible for the better hearing ability in high fit subjects. Perhaps the well-known exercise training adaptations that occur in skeletal muscle carry over in some degree to the stria vascularis, a relatively high vascular area on the outer wall of the scala media. The scala media is one of three tubes (scala vestibuli and scala tympani) supporting vestibular and auditory function. It contains the organ of Corti, which contains the mechanically sensitive hair cells. Although speculative, it is possible that increases in oxidative enzymes, myoglobin, and visceral organ blood flow in persons having high cardiovascular fitness (Holloszy & Booth, 1976) may also positively affect oxygen delivery and extraction in structures requiring energy in the inner ear. In summary, results of the present study indicated that 8 weeks of cardiovascular exercise training enhanced hearing ability as shown by improved pure-tone hearing levels at two frequencies (2 and 3 khz) and reduced TTS at the evaluated frequencies (2, 3, and 4 khz). Persons with low to moderate cardiovascular fitness who participated in a cardiovascular exercise training program of at least 8 weeks experienced benefits to their hearing ability as well as their cardiovascular fitness. In conclusion, both cardiovascular function and hearing ability are amenable to improvements following a moderate intensity exercise regimen lasting 2 months. References Alessio HM, Hutchinson KM. Effects of submaximal exercise and noise exposure on hearing loss. Res Q Exerc Sport 1991; 62: 413¹9. American College of Sports Medicine. Guidelines for exercise testing and prescription. 3rd ed. Philadelphia: Lea & Febiger, American National Standards Institute. Maximum permissible ambient noise levels for audiometric test rooms (ANSI S3.1). New York: ANSI, American National Standards Institute. Specifications for audiometers. New York: ANSI, Burns W, Hinchcliffe R. Comparison of the auditory threshold as measured by individual pure tone and by Bekesy audiometry. J Acoust Soc Am 1975; 29: 1274¹7. Holloszy JO, Booth FW. Biochemical adaptations to endurance training in muscle. Ann Rev Physiol 1976; 38: 273¹91. Hutchinson KM, Alessio HM, Spadafore M, Adair R. Effects of noise and low-intensity exercise on temporary threshold shift. Scand Audiol 1991; 20: 121¹7. Ismail AI, Corrigan DL, MacLeod DF, Anderson VL, Kasten RN, Elliot PW. Biophysiological and audiological variables in adults. Arch Otolaryngol 1973; 97: 447¹51. Kirkwood D. Washington starts waking up to hazards of recreational noise. Hear J 1992; 45: 13¹24. Manson J, Alessio H, Cristell M, Hutchinson K. Does cardiovascular health mediate hearing ability? Med Sci Sports Exerc 1994; 26: 866¹71.

Supplementary Online Content

Supplementary Online Content Lin FR, Ferrucci L. Hearing loss and falls among older adults in the United States. Arch Intern Med. 2012;172(4):369-371. eappendix. Audiometric Assessment and Other Study