Abstract
Background
Backpacking is a popular recreational activity, yet the differential experiences of women are unknown. The objective was to compare the experiences of women backpackers and determine the extent to which injuries and illnesses limit endurance outdoor recreational activities.
Methods
Prospective cohort survey. 334 persons who hiked the Appalachian Trail for ≥ 7 days were interviewed. At the end of their hike, 280 subjects completed a questionnaire. Male hikers were controls.
Results
Women comprised 26% [72/280] of the sample. The mean [± SD] duration of hiking was 144 ± 66 days covering 1570 ± 680 miles. Fifty-seven percent [41/72] of women and 72% [150/208] of men attained their goal (P = .02). The occurrence of individual musculoskeletal problems, such as strains, sprains, arthralgias, tendonitis, and fractures, were similar (P = .9). The occurrence of diarrhea (56%) was similar (RR 1.0; P = .9).
Of regularly menstruating women, 87% [43/49] had menstrual changes while hiking, such as change in frequency 45% or character 43% (RR 3.1; 95% CI: 2.0 to 4.8; P < .001). Shortened duration of menses was most common (41%). Amenorrhea occurred in 22% [11/49] including 5 of 25 taking oral contraceptives pills (OCPs). Breakthrough bleeding occurred in 20% [10/49].
Conclusions
Women had similar experiences as compared to men when backpacking. Menstrual changes were very common including amenorrhea. This prolonged amenorrhea raises concern for potential bone mineral density loss, and OCPs should be considered to prevent such loss.
Keywords: women’s health, backpacking, women, injury, camping, amenorrhea, estrogen
Hiking and backpacking are among the most popular and fastest growing outdoor recreational activities in the United States. In 2002, 34.7% of adult Americans hiked and 11.5% backpacked.1,2 Backpacking is one of the fastest grouping outdoor activities with participation increasing 54% from 1995 to 2000.1,2 In 2002, 32% of American women participated in outdoor adventure activities with 7.4% of women backpacking and 29% hiking.3,4
In the 1980’s, research demonstrated that women are less likely than men to believe that they are entitled to leisure and recreation.5,6 While seemingly outrageous, even today, women engaging in outdoor recreational activities are likely to feel constrained by personal safety concerns, inadequate facilities and information, insufficient funds, and outdoor pests.7 Participation in camping or hiking alone in remote areas may arise from fear of sexual assault or harassment.6
There are few studies examining wilderness morbidities and mortalities. There are no studies which examine the differential experiences of women. Among women backpackers, there has been no investigation.
Our study examines the experiences of female backpackers on the Appalachian Trail. Our major objective is to determine if there exist differential experiences in regards to injuries, illnesses, or gynecological concerns.
Methods
Data for this study were obtained via a prospective, observational cohort survey. The prospective design sought to incorporate a diverse group of backpackers, including those hiking only a section as well as the entire Appalachian Trail. In the initial recruitment stage, participants were approached while hiking and interviewed. Interviews occurred for 12 weeks from May 15 through August 5, 1997 over 1600 km stretching from New Hampshire to North Carolina. If hikers met the inclusion criteria of hiking for >7 days, the nature and purpose of the study were explained. Proposed participants were given a stamped postcard requesting their address and medical problems experienced. Of the 353 hikers approached, 352 agreed to participate, but 18 were excluded by a lack of a permanent address.
In the second phase of the study, at a 3 month follow up interval, a 4 page questionnaire was mailed to participants. The questionnaire assessed demographic information, achievement of the individual’s original goal, and occurrence of medical problems. The 25 most common medical problems of the initial recruitment phase were assessed via a form with checkboxes. Women were given a one page supplement regarding gynecological issues including: past history, menses in the prior year, and changes during hiking.
All continuous variables are compared using t tests. Comparison of categorical data is performed using chi-square tests. Comparisons of cohorts are expressed via the relative risk (RR) and 95% confidence interval (CI). Case-control comparisons are expressed via the odds ratio (OR) and 95% CI. Institutional review board approval was obtained.
Results
Of 334 backpackers, 280 responded with completed surveys. Women comprised 26% [72/280] of the sample. Median follow up time was 30 days from finishing hiking. Demographic and comparative gender data are presented (Table 1). When the 25 most common injuries and illnesses were examined, there were few statistically significant differences between genders. When musculoskeletal injuries were compared, there were no significant differences between genders in musculoskeletal injuries. The rate of fractures (RR 1.1; 95% CI: 0.3 to 4.0; P = .8), joint pain (RR 1.0; 95% CI: 0.7 to 1.3; P = .7), sprains (RR 1.2; 95% CI: 0.7 to 2.3; P = .6) and strains (RR 1.3; 95% CI: 0.7 to 2.3; P = .7), and other musculoskeletal problems were similar (P = .9). The occurrence of diarrhea was similar (RR 1.0; 95% CI: 0.8 to 1.3; P = .9); though, women performed water disinfection more consistently (OR 1.47; P = .03). There was no correlation between weight loss and diarrhea. Women self-reported more hypothermia (RR 3.4; 95% CI: 1.2 to 9.9; P = .02), paresthesias (RR 1.4; 95% CI: 1.1 to 2.0; P = .03), and sunburns (RR 1.9; 95% CI: 1.3 to 2.8; P < .01).
Table 1.
Characteristics of Subjects by Gender
| Characteristic | Men (n = 208) | Women (n=72) | P Value |
|---|---|---|---|
| Mean ± SD or Number (%) | |||
| Age (years) | 35 ± 15 | 33 ± 13 | 0.34 |
| Length of trip (days) | 138 ± 60 | 144 ± 66 | 0.47 |
| Length of trip (miles) | 1660 ± 690 | 1570 ± 680 | 0.38 |
| Weight loss (kg) | 6.6 ± 6.4 | 3.5 ± 6.0 | 0.0003 |
| Weight loss (%) | 7.9 ± 6.8% | 4.6 ± 7.7% | 0.001 |
| Backpack weight (kg) | 19.6 ± 3.9 | 17.3 ± 3.6 | <0.001 |
| Backpack weight (% body weight) | 25.0 ± 5.9% | 27.9% ± 5.4% | <0.001 |
| Treated water consistently | 45 (21%) | 22 (31%) | 0.03 |
| Had diarrhea | 116 (56%) | 40 (56%) | 0.90 |
| Days of diarrhea per month | 0.7 ± 1.2 | 1.0 ± 2.1 | 0.26 |
| Consistent hand washing | 108 (52%) | 47 (66%) | 0.01 |
When genders were compared, 57% [41/72] of women and 72% [150/208] of men attained their goal (P = .02). The primary reasons for women, abandoning hiking earlier than planned, were time limitation (27%), injury (20%), financial (16%), social / family constraints (13%), and psychological (13%). Observation revealed that women often hiked with companions, yet the rate of abandoning hiking because of a hiking partner quitting was similar between genders (4%). Environmental and dietary reasons were not significant factors (4%). Prior experience did not statistically increase success (OR=1.6; 95% CI: 0.9 to 3.0; P = .1). There was no overall difference in prior backpacking experience (P = .2). However, the proportion of hikers with less than a weekend’s backpacking experience was greater among women (39%, RR 1.8; 95% CI: 1.2 to 2.7; P = .003).
Women’s backpacks were lighter than men’s, and even indexed as percent baseline body weight, women carried slightly lighter loads (Table 1). Men lost twice as much weight (P < .001). With adjustment for baseline weight, there is a significant difference of percentage weight loss (men = 8 ± 7%, women = 5 ± 8%; P = .001).
Gynecological Issues
Sixty-four women fully completed the gynecologic survey (Figure 1). Twenty percent [13/64] were post-menopausal. Oral contraceptives pills (OCPs) were utilized by 39% [25/64]. Two hikers used depo-provera, and their induced amenorrhea is not included in further discussion. Of regularly menstruating women, 87% [43/49] had menstrual changes, such as change in frequency or character while hiking (RR 3.1; 95% CI: 2.0 to 4.8; P < .001) compared to the prior year. The most common change in menses was a shortened duration (n=21). Seven women had a shorter frequency of menses and four had irregular menstrual frequencies.
Figure 1.
Profile of Gynecologic Status
Twenty-two percent [11/49] became amenorrheic while hiking, only one of whom had skipped any menses in the year prior. Despite taking OCPs, five women were amenorrheic during their hiking trip. Breakthrough bleeding occurred in 10 women including 6 women on OCPs. In the year prior, only 3 women had reported breakthrough bleeding (OR 3.9; 95% CI: 1.01 to 15.3; P = .04). There was no difference (P = .9) in the average OCP estrogen content of either those with breakthrough bleeding (33 ± 3 mcg) or amenorrhea (34 ± 2 mcg) as compared with those in whom this did not occur (32 ± 4 mcg). There was no statistical difference between hike duration (P = .08), distance (P = .1), initial weight, (P = .8), percent weight loss (P = .4), or pack weight (P = .9) among those with amenorrhea or breakthrough bleeding than with those who did not.
Discussion
In comparing the experiences of women and men backpackers, their general experiences were remarkably similar. Both the distance and duration of women’s backpacking trips were similar to men’s. Women did not experience significantly more musculoskeletal problems.
Women were slightly less likely to achieve their individual goal. It was unclear as to why this occurred. The reasons given for quitting early were similar to that of men. While earlier research suggested environmental factors, such as safety or outdoor pests, were limitations to outdoor recreation,7 they were not significant reasons for leaving once in the outdoors in this study.
The most significant medical issue arising with long-distance backpacking was gynecologic abnormalities A significant proportion (22%) of women backpackers experienced amenorrhea. While many respondents commented as to the practical benefit of amenorrhea during hiking, the medical implications are of concern. Complications of intense exercise include: low estrogen and progesterone with risk of loss of trabecular bone and early osteoporosis.8,9 In athletes, the observed prevalence of amenorrhea is 5 to 66%.10,11 Our study was consistent with this in which 22% had amenorrhea. In a study of adult female athletes, 72% of the amenorrheic women were either osteopenic or osteoporotic.12
While no study of female backpackers has been performed, likely those with amenorrhea also experience bone mineral density (BMD) loss. The duration of amenorrhea and body weight are predictors of BMD.12 Weight-bearing exercise does not offset the negative effect of decreased estrogen on the skeleton of amenorrheic athletes.12 Though the episode of long distance backpacking and the amenorrhea may be only temporary, the BMD loss may be irreversible in spite of resumption of menses.11,13,14 This raises concern over a possible later increased risk for premature osteoporotic fractures.
Amenorrheic athletes using estrogen in doses used for menopausal women have shown maintenance of BMD but no gains.15 With OCP doses, BMD has improved in amenorrheic females.16 In our study, several women who took standard OCPs had difficulties with breakthrough bleeding. This may be indicative of the need for higher dose OCP in these metabolically active women. No pharmokinetic study of estrogen metabolism has been performed in active women. Likely, the nutritional,17 weight,18 and activity changes of backpacking may alter production and metabolism of estrogen.
Official recommendations encourage amenorrheic women to ingest ≥ 1500 mg of calcium daily to assure calcium balance.11,19,20 In backpacking, the typical diet of starches and dehydrated foods does not provide this. Further investigation is warranted as it has also been shown that current calcium intake is unrelated to BMD for either amenorrheic and eumenorrheic athletes.12
Limitations
Limitations of this study include the small sample size for gynecological comparisons among subgroups. Indeed this portion of the study was underpowered to detect statistical differences. For weight loss and amenorrhea, we calculate the sample sizes necessary for 80% power to be 49 persons.
Conclusions
Women had similar experiences when backpacking as compared to men. Our evaluation of women’s issues revealed that menstrual changes were very common including amenorrhea. Mid-dose OCPs should be considered to prevent bone mineral density loss while amenorrheic for extended backpacking trips.
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