Exercise-associated pain (EAP) often results from intense exercise. Exercise-associated pain is described as a threat to fluid movement and maximum performance (14), and it is suggested that individuals are at an increased risk of injury if strenuous activities are undertaken while this pain persists (4). Although various treatment modalities exist for the relief of EAP, analgesics, including both nonprescription and prescription nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen, are one of the most popular choices. Epidemiological research shows a pervasive use of prescription and nonprescription analgesics in various populations (2,3,6,13,19–23), with much of this use occurring without regard for label directions and the potential for adverse reactions (Table 1). Prevalent use, ranging from 17 to 83%, has been reported. The large range of prevalence may be attributed to differences in the definition of “use,” the length of time over which use was measured, and whether interest was in use of prescription and/or nonprescription analgesics (6,13,22). Among Food and Drug Administration regulated drugs, acetaminophen, ibuprofen, and aspirin are the top 3 medications used by males and females athletes, whereas naproxen ranks 12th (6,13).
Reasons for and rates of use vary between the general and athletic populations. National Health and Nutrition Examination Survey 1999–2000 data reported 14% of Americans (aged 20 years and older) use nonnarcotic analgesics daily or nearly every day over the course of a month to treat various ailments, including musculoskeletal pain (13). This is consistent with other research that reports daily use of nonprescription analgesics in approximately 15–27% of U.S. adults (aged 18 years and older) and frequent weekly use in an additional 29% of the population (22). Daily users of nonprescription analgesics in the general population are reported to be less concerned about potential side effects compared with those who use analgesics less frequently (22). Additionally, use of doses in excess of label directions is more prevalent in those who use nonprescription analgesics compared with prescription users, at 26 and 8%, respectively (22). Forty percent of nonprescription analgesic users cited muscle ache as their primary motivation for use (22). Data extrapolation translates these values into approximately 36 million U.S. adults who use nonprescription analgesics daily, including approximately 14 million who use these specifically for muscle ache (22). National Health and Nutrition Examination Survey data reveal that the use of nonprescription analgesics doubled between 1988 and 2000, with specific increases in frequent monthly use (≥14 days per month) in 20- to 39-year-old age groups (13). Alarmingly, self-administration of analgesics for muscle pain relief is reported to begin at 11.5 ± 2 years of age (2).
Overall rates of analgesic use are higher in some athletic populations, with specific samples of high school (21), collegiate (19,23), and professional (3,20) athletes reporting not only prevalent use but also dangerous motivations behind this behavior. Daily use of nonprescription analgesics has been reported in 6 and 15% of college and high school athletes, respectively (21,23). In athletic populations, daily use is found to be greater in those who believe NSAIDs aid performance, those who decide independently to use NSAIDs, and those who use NSAIDs to block pain (21). Athletes cite a desire to accelerate healing, to permit an earlier return to competition, to mask injury with prophylactic use, and to improve performance as reasons for analgesic use (14,19). Additionally, inappropriate dosing regimens and concomitant use of multiple analgesic products in anticipation of a synergistic effect have been reported in athletic populations (3). High rates of use in athletes have raised speculation that these drugs are being used not only for therapeutic purposes but also prophylactically in an attempt to conceal injury and/or facilitate performance (14).
Although use of analgesics has been characterized in the general U.S. population (18 years and older), adolescent population (13 ± 1 years), and athletic populations, to our knowledge, the use of analgesics in college-aged (18–24 years) students, specifically for EAP, has not been reported in literature. Age-related chronic ailments such as arthritis and participation in team sports resulting in musculoskeletal injury may inflate rates of use in general and athletic populations, respectively, relative to college-aged individuals. The specific interest in analgesic use for EAP in a recreationally-trained college-aged population was driven by research that reports muscle ache as a primary motivation for use of analgesics (22) and high rates of analgesic use in young individuals (6,13,19,21,23). Furthermore, research reports significantly reduced protein synthesis and satellite cell activity in young participants who combine analgesics and exercise (8,10,17,18).
Mackey et al. (8) reported that daily doses of indomethacin, beginning 4 days before a marathon and continuing 8 days after a marathon, significantly reduced satellite cell proliferation postrun in young trained males (25 ± 3 years). In addition, indomethacin infused in the hours before, during, and after a single bout of isokinetic resistance exercise has been found to significantly reduce satellite cell proliferation in young recreationally trained males (23 ± 3 years) (10). Trappe et al. (18) found orally administered nonprescription doses of ibuprofen and acetaminophen significantly reduced postexercise mixed muscle protein synthesis in response to an acute bout of isotonic exercise performed by young males (25 ± 3.5 years), by way of suppression of hormones that mediate protein synthesis (17).
In light of data demonstrating acute drug-induced inhibition of protein synthesis and satellite cell activity, the primary objective of this study was to determine if recreationally trained college-aged individuals use analgesics in ways that are similar to those used in research studies that show negative effects on these regenerative processes. Secondary objectives were to examine patterns and behaviors associated with analgesic use and to assess whether specific characteristics of individuals and their exercise habits predict analgesic use for EAP.
Experimental Approach to the Problem
The 16-item instrument was developed after a review of pharmacoepidemiological literature describing motivations, patterns, and behaviors associated with analgesic use. Analgesics were defined for respondents on the questionnaire as prescription and nonprescription NSAIDs and acetaminophen, with both generic and brand names provided for clarification. With previous research highlighting EAP as a primary motivation for use, the questionnaire began with questions related to exercise, including type (aerobic and/or resistance), number of weekly aerobic sessions (0–7+), number of weekly resistance sessions (0–7+), and length of time performing regular exercise. “Regular” exercise was defined as performing exercise ≥3 times per week, and respondents were able to indicate how long they had engaged in regular exercise (<6 months or ≥6 months).
The questionnaire then asked about the use of analgesics specifically for relief from EAP (the primary dependent variable in subsequent analyses). “Use” was defined as any use, with no specific restrictions on this definition, other than specifically for EAP. If participants indicated that they never used analgesics for EAP, they were instructed that the questionnaire was complete and to submit the questionnaire. If a participant indicated use of analgesics for EAP, they were directed to proceed with the next question.
The remaining questionnaire items included behavioral information on weekly frequency of use, daily frequency of use, directed vs. self-determined use, use of prescription and/or nonprescription analgesics, type of analgesic chosen (acetaminophen, ibuprofen, naproxen, or others), and number of pills consumed per typical dose. Four items related to adherence to label instructions were posed, including likeliness to self-adjust (increase or decrease) the recommended dosage size and/or the number of hours instructed to wait before the consumption of a subsequent dose. A final item sought to establish the likeliness to use prophylactically in anticipation of pain. Responses to behavioral questions were measured on a 5-point scale.
Three experts in survey design and pharmacy examined the instrument for content validity. Test-retest reliability was then established before formal data collection. To determine test-retest reliability, the instrument was administered twice to college-aged students (first administration, n = 33; second administration, n = 30) enrolled in a twice-weekly University resistance training course, with the second administration occurring 48 hours after the first. To ascertain interpretation stability throughout all components of the questionnaire, the 16 items were grouped into the following constructs: frequency of exercise, frequency of analgesic use, self-determined/directed use, type of analgesic chosen, typical dose size, and behaviors regarding adherence to label directions. Pearson's correlation coefficients for these variables between the first and second administrations were 0.60, 0.76, 0.83, 0.95, 0.82, and 0.83, respectively.
The total sample comprised of 127 male and 136 female (N = 263) participants, who met inclusion criteria. Inclusion criteria were a recreational training status and an age between 18 and 24 years. Recreationally trained was operationally defined as current participation in any level of aerobic and/or resistance exercise. Collegiate athletes and military personnel were excluded because of their advanced training status. Because the objective of the study was to determine prevalence of use of analgesics for EAP, patrons at the University exercise facility and students enrolled in activity courses (aerobics, jogging, resistance training, and racquetball) were orally invited to complete the questionnaire. If invited participants agreed to complete the questionnaire, they were provided with an oral description of the content of the instrument and informed their participation was voluntary. No incentives were provided for participation. With age and gender being the only demographic variables collected and because no other identifying information was obtained, participants were informed that their voluntary completion of the questionnaire indicated consent. This study was approved by the University's Institutional Review Board.
Procedures and Statistical Analyses
The primary outcome variable was the use of analgesics for relief of EAP, and all respondents (N = 263) were classified as either a user or nonuser based on self-reported data. For both users and nonusers, descriptive statistics and frequency counts related to exercise were calculated, including weekly frequency of both aerobic and resistance exercise and length of time (<6 months or ≥6 months) performing regular (≥3 times per week) exercise. For users, descriptive statistics and frequencies were determined for items related to analgesic use for EAP, including weekly frequency of use, daily frequency of use, use of prescription and/or nonprescription analgesics, type of analgesic chosen (ibuprofen, naproxen, aspirin, acetaminophen, and multiple), and behaviors relating to adherence to label directions.
For logistic regression analysis, 4 predictor variables (gender, weekly frequency of aerobic exercise, weekly frequency of resistance exercise, and length of time performing regular exercise) were first examined separately to evaluate their ability to predict analgesic use for EAP and to calculate unadjusted odds ratios with 95% confidence intervals. Pearson's chi-square test was used to determine potential significant differences between users and nonusers in gender (male or female) and length of time performing regular exercise (<6 months or ≥6 months), whereas t-tests were used to determined potential significant differences between users and nonusers in weekly frequency of aerobic and resistance exercise (0–7 days per week). The reference category for gender was female, and the reference category for length of time performing regular exercise was ≥6 months of regular exercise. After individual analysis for each predictor, all 4 were then included in a multivariable logistic regression model to examine adjusted odds ratios with 95% confidence intervals. Frequency of aerobic and resistance exercise were treated as continuous predictors in the model, whereas gender and length of time performing a regular exercise were treated as categorical predictors. Statistical analyses were performed using SPSS (version 17.0; SPSS, Inc., Chicago, IL, USA), and values of p < 0.05 were considered statistically significant.
Within the total sample, the average weekly frequency of aerobic exercise was 3.60 ± 1.48 sessions (mean ± SD), whereas the average weekly frequency of resistance exercise was 2.8 ± 1.5 sessions. Within the total sample, 80 respondents (30.4%) reported performance of regular exercise for a period <6 months, whereas 183 (69.6%) respondents reported performance of regular exercise for a period ≥6 months. Thus, most respondents were meeting recommendations for aerobic and resistance exercise and had been doing so regularly for a period of at least 6 months. Ninety-five respondents (36.1%) reported analgesic use for the relief of EAP, and 168 respondents (63.9%) reported no use of analgesics for EAP. Table 2 presents characteristics of the total sample and a comparison of users and nonusers with respect to the 4 variables considered as predictors in the multivariable logistic regression model. Figure 1 presents data illustrating weekly frequency of resistance training for users and nonusers.
Patterns of Analgesic Use
Fifty-nine percent of users reported analgesic use once per week, and 26.1% of users reported use twice per week (mean ± SD weekly use, 1.64 ± 0.99 days). On the days when analgesics were used for EAP, 77.4% of users consumed 1 dose per day, whereas 21.5% of users consumed 2 doses per day (mean ± SD daily use, 1.24 ± 0.45 times). More than 60% (63.3%) of users consumed 2 pills per typical dose, whereas 21.1% of users consumed 3 pills per dose. One pill and 4 pills per typical dose were consumed by 11.1 and 4.4% of users, respectively.
Eighty-three percent of users reported independently deciding to use analgesics for EAP, 1.1% were directed to use by a personal health professional and 16.3% reported that their decision was both internally and externally motivated. The overwhelming majority (94.6%) reported use of nonprescription analgesics, while 1.1% of users used prescription only, and 4.3% of users used a combination of prescription and nonprescription analgesics. Ibuprofen was chosen by 48.4% of users, followed by 44.0% of users who chose multiple types, 4.4% who chose naproxen, and 3.3% who chose to use acetaminophen.
Behaviors Related to Analgesic Use
Items related to analgesic-use behavior included (a) likeliness to follow label directions, (b) likeliness to take a dose in excess of label directions, (c) likeliness to take a dose smaller than label directions, (d) likeliness to wait the directed number of hours before taking subsequent dose, and (e) likeliness to take in anticipation of soreness. Responses to these questions were measured on a 5-point scale, with 1 indicating “not at all likely” and 5 indicating “very likely.” Data for these items can be found in Table 3. Among self-identified users (n = 95), only 89 users provided responses to the first item regarding likeliness to follow label directions. Less than half of these respondents (n = 41, 46.1%) described themselves as very likely to follow label directions. Those users who identified themselves as very likely to follow label directions were directed to skip the 3 items related to likeliness to self-adjust dosage size or schedule and answer the item related to prophylactic use. Those users (n = 48, 53.9%) who characterized themselves as anything less than “very likely” to follow label directions were directed to complete the 3 items related to the tendency to self-adjust dosing guidelines and the item related to prophylactic use (Table 3).
Within the portion of the sample who reported self-adjusting dosage guidelines (n = 48), approximately 25% of users reported being either “somewhat” (16.3%) or very likely (8.2%) to take a dose exceeding recommendations. Conversely, only 10.2% of users reported being either somewhat (6.1%) or very likely (4.1%) to take a smaller-than-recommended dose. Fifty-one percent of users described themselves as being either somewhat (12.2%) or very likely (38.8%) to wait the directed number of hours before taking a subsequent dose, whereas less than one-fourth of these users reported being “not at all” (8.2%) or “not very” (14.3%) likely to wait the directed hours. Twelve respondents failed to provide a response to the item concerning prophylactic use; thus, only 83 responses to this question were obtained. The tendency to take prophylactically was not seen in this population, with 63.9% reportedly “not at all likely” to use prophylactically in anticipation of EAP.
Predictors of Analgesic Use for Exercise-Associated Pain
In addition to determining prevalence of use, the secondary objective of this study was to evaluate specific characteristics of individuals and their exercise habits that might potentially predict analgesic use for EAP. To address this, 4 variables were examined in a logistic regression model for their potential to predict use: gender, length of time performing regular exercise, weekly frequency of aerobic exercise, and weekly frequency of resistance exercise. With each potential predictor first considered separately, gender was the only variable revealed as a significant predictor of analgesic use (p = 0.043), with male participants being less likely to use analgesics for EAP than female participants (29.9 vs. 41.9%, respectively; unadjusted odds ratio = 0.59). With all 4 predictors considered concurrently, the omnibus test was nonsignificant (p = 0.199), suggesting that these 4 predictor variables considered concurrently do not significantly contribute to the prediction of analgesics use for EAP in this population. Adjusted and unadjusted odds ratios with 95% confidence intervals are presented in Table 4.
Although analgesics are used to manage a variety of pain conditions, the primary objective of this study was to examine the prevalence of use specifically for EAP in a sample of recreationally trained college-aged students. Several factors drove the interest in obtaining data specifically for EAP. These factors included research that shows high rates of analgesic use for EAP in the general population (22), high rates of use in athletes for both pain management and performance concerns (3,5,19–21,23), increasing rates of use in young individuals over the last 2 decades (13), and experimental research to demonstrate a drug-induced attenuation of reparative processes in skeletal muscle in young participants when exercise is accompanied by analgesics (8,10,17,18). This study sought to determine if young recreational athletes use analgesics for EAP relief in ways that resemble the administration of such drugs in studies that report a suppression of regeneration when exercise is accompanied by nonprescription analgesics (8,10,17,18). If so, the results of these experimental studies hold significant implications for athletes, coaches, and trainers striving to improve muscular fitness.
Within the current sample, 36% of recreationally trained college-aged students reported use of analgesics for EAP. The majority use analgesics 1–2 times per day (98.9%) on 1–2 days per week (84.8%). Although these rates of use are lower than those reported for the general population (13,22), those studies examined use for any ailment and not EAP exclusively, thus comparisons are difficult. However, EAP was cited as one of the top 3 reasons for use in previous studies of the general population (13,22). Rates of use for EAP in the current sample are lower than rates reported for athletic populations, with data from studies of athletic populations averaged to roughly 53% across age groups and competition levels (3,5,19,21,23).
Ninety-five percent of users in the current sample reported selecting nonprescription analgesics, which agrees with the large percentage (82.6%) who reported independently deciding to use analgesics as opposed to being directed to use. It seems logical to assume that an association exists between independently deciding to use analgesics and selecting nonprescription analgesics. Those who independently decide to use analgesics are reported to be 2.5 times more likely to use NSAIDs daily (21). Although the 80% of users in the current sample who report independently deciding to use analgesics for EAP is higher than the 64% reported in a sample of collegiate athletes (23), the data are consistent with other studies that show most analgesic users independently decide to medicate (2,5,23).
Nonprescription analgesics are often selected over prescription formulations due to a presumption that they are safer and also because they are simply easier to obtain (22). This perception of their relative safety and the ease with which they can be obtained may potentially explain both their widespread use and the tendency to consume doses that exceed recommendations. Data from users in the current sample supports this contention, with 53.9% characterizing themselves as unlikely to follow label directions. Approximately 25% of users in the current sample reported a likeliness to exceed the recommended dosage, which is consistent with our finding that 21% report taking 3 pills of their self-selected analgesic per dose. This value is comparable to the 26% of the general population who reportedly exceed recommended doses of nonprescription analgesics (22), with a similar tendency reported in athletic populations (23). Importantly, research that demonstrates a drug-induced suppression of regeneration used dosages in accordance with label directions. It seems logical to assume that greater doses of these medications would be associated with greater inhibition of muscular regeneration. Rates of prophylactic use were low in the current sample and do not compare to data presented for collegiate athletic populations (21,23), possibly because of the lack of pressures related to competition (19).
In the current sample, nonprescription ibuprofen was selected by 48.4% of users, similar to findings from previous research (6,13,22,23). Interestingly, 44% reported use of multiple preparations of analgesics (acetaminophen, ibuprofen, and naproxen). With the current questionnaire, it was not possible to ascertain if the multiple preparations were used concurrently; however, 7.2% of users in the general population reportedly use 2 or more analgesics nearly every day during a month (13), and 8.9% of elite soccer players use at least 2 preparations in the 72 hours preceding tournament play (20). Use of multiple types in the current sample may possibly suggest how these medications are procured, as research has shown 58–60% of a sample of collegiate athletes obtained analgesics from teammates or friends (19). Other research shows 47% of a sample of collegiate athletes purchased these drugs as opposed to receiving them from an athletic trainer or physician, and these were also more likely to exceed the recommended dose (23). In the current sample, behavior deviating from label directions was more apparent in the tendency to self-adjust the dosage size as opposed to the dosage schedule, as the majority of the sample described themselves as likely to wait the directed number of hours before taking a subsequent dose. However, this is partially explained by the fact that users in the current sample only report use for EAP 1.2 ± 0.5 times per day on the days when these drugs were used.
When considered separately, gender was the only significant predictor of analgesic use for EAP, with male users being less likely than female users to use analgesics for EAP. This finding was not maintained after adjusting for other predictors. Studies of the general population show rates of use of acetaminophen, ibuprofen, and aspirin are greater in women than in men in every age group (6). Studies of the general U.S. population report that men are more likely to use analgesics for muscle ache (22), whereas studies of the athletic populations show female athletes' rate of analgesic use to be equal to or greater than that of male athletes (20). With all predictors considered concurrently, the ability to predict users from nonusers was not successful.
Generally, EAP is acute. It typically manifests as delayed onset muscle soreness, with symptoms that appear approximately 24 hours postexercise and persist for 48–72 hours (4). The data in the current study suggest analgesic use for EAP is also acute, and there seems to be an association between twice-weekly performance of resistance exercise and analgesic use. Although it is chronic use, rather than acute use, that is associated with long-term renal, gastrointestinal, and cardiovascular complications, acute use of nonprescription analgesics in conjunction with exercise has been shown to significantly inhibit normal increases in mixed muscle protein synthesis after acute resistance exercise in humans (17,18) and diminished satellite cell activity (8,10). Furthermore, other research shows the detrimental effects, with analgesic-treated animals exhibiting persistent deficits in force generation in response to electrical stimulation (7), reduced satellite cell proliferation (1,11,12), reduced satellite cell differentiation (9,15), reduced satellite cell fusion (9), reduced hypertrophy (11), reduced mixed muscle protein synthesis (16), and inhibition of the repeated bout effect (7). Acute use for acute pain relief resulting from exercise is therefore cause for concern, as it may impede many indices of muscular development.
Exercise-associated pain is commonly experienced after resistance exercise. Guidelines for resistance exercise put forth by several national health agencies include a general recommendation for 2–3 total body sessions separated by 48 hours. Although guidelines for the minimum amount of time required for recovery are included in the recommendation (48 hours), guidelines for the maximum number of days that should pass between resistance sessions for the same muscle group are lacking. Users of analgesics for EAP in the current sample reported resistance exercise on an average of 2.62 ± 1.13 times per week, and non-users reported resistance exercise about 2.88 ± 1.67 times per week. Although both users and nonusers are in-line with recommendations, closer inspection of frequency counts for each weekly frequency of resistance training (0–7 times) revealed curious and substantial differences between users and nonusers, particularly at the twice weekly level (Figure 1).
Twice weekly resistance exercise was reported by 23% of nonusers vs. 42% of users. Similarly, 25% of nonusers reported resistance training 3 times per week vs. 30.5% of users. With the current instrument, it is not possible to ascertain the type of resistance program performed (total body or split routine) or how many days passed between reported resistance training sessions. However, if too many days pass between resistance workouts, soreness is more likely to develop in response to the subsequent bout. This may be 1 factor that explains the acute use suggested by the data. If users are using acutely for acute EAP, then experimental research suggests such behavior would be counterproductive to muscular fitness goals (1,7–12,15–18). Thus, a caveat exists in that although college-aged individuals are meeting current resistance training recommendations, this frequency of exercise (2–3 times per week) seems to be associated with analgesic use for EAP.
In summary, approximately 36% of the current sample report analgesic use for EAP, and this use can be characterized as acute based on examination of weekly and daily frequencies of exercise and analgesic use. Behaviors deviating from label directions were more prevalent in items related to dose adjustment, as the acute nature of use for EAP reported by respondents lends itself to complying with guidelines for subsequent dosing. The rate of use reported in this study is somewhat difficult to compare with in other studies that examined analgesic use for any type of ailment and not exclusively EAP. In consideration that analgesics are used to treat a variety of pain conditions, it is reasonable to conclude absolute use is underrepresented in this sample. Because most users report not only self-determining use but also self-adjusting the recommended dosing, coaches and trainers may well be unaware if their athletes or clients are using such medications. In light of experimental research reports on the potential negative consequences of such drugs on muscular development, it seems prudent for coaches and trainers to be aware of the tendency of recreational exercisers and athletes to use such drugs. In addition, coaches and trainers should inquire about the use of such drugs in their athletes, and take proactive steps to educate clients about the potential of these drugs to inhibit the development of muscular fitness.
More than 1 in 3 students in the current sample report taking analgesics to alleviate pain resulting from exercise, with data reflecting acute use for acute pain. Unfortunately, this type of use has been shown to be counterproductive to the development of muscular fitness, as both prescription and nonprescription analgesics taken in conjunction with a single bout of exercise have been shown to suppress mixed muscle protein synthesis and satellite cell activity in humans (8,10,17,18). This may be a classic example of “one step forward and two steps back.” Although certain potential side effects of NSAIDs are well known, including increased risk of renal damage, gastrointestinal bleeding, and cardiovascular events, their effects on muscle regeneration postexercise are less well known. In light of the potential to suppress regeneration unintentionally in an attempt to alleviate pain and consideration of the ease with which these drugs may be obtained, it seems necessary for coaches and trainers to educate athletes on this risk and encourage a conservative approach to their use for EAP. Coaches and trainers should also be aware that female athletes may be more likely to use analgesics for EAP. Obviously, proper and systematic progression of exercise parameters (frequency, intensity, and volume) is necessary to allow physiological adaptation to the stresses of exercise. Furthermore, an amendment to current resistance training recommendations from national health entities to define clearly the maximum number of days that should pass between resistance training workouts should potentially be considered, as this could reduce pain resulting from exercise and the subsequent perceived need for analgesics.
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