Low Energy Intake Leads to Body Composition and Performance Decrements in a Highly-Trained, Female Athlete: The WANDER (Woman’s Activity and Nutrition during an Extensive Hiking Route) Case Study

Abstract

Thru-hiking requires high energy intake to support performance and reduce injury risks. Currently, there is limited information on the dietary demands, the practical considerations for optimal nutrient intake, and the negative consequences associated with reduced caloric intakes during a thru-hike, particularly in women.

Objective

This case study’s purpose was to quantify energy intake vs energy expenditure during a thru-hiker’s trek and assess its relationship to performance and health.

Methods

A highly trained, female thru-hiker (Age (yrs): 62, Ht (cm): 157, Wt (kg): 53.5, BMI (kg/m²): 21.7, %BF: 26.0) embarked on a 4-month journey through the Pacific Crest Trail, USA. The athlete’s body composition and 3-day diet record were assessed before (PRE) and after the hike (POST). During the hike, she tracked her diet and performance daily and completed a wellness survey each time she reached a town-check point. Data were analyzed for descriptive (weekly averages, means ± SD) and frequency statistics.

Results

She spent 10 wk (∼70 days) on the trail and hiked 1,506.35 km (26.1 ± 3.2 km/day) with an estimated energy expenditure of ∼2334 ± 351 kcal/day. During the hike, she under consumed calories (1285.3 ± 103 kcal) and dietary carbohydrate (169.5 ± 19.5g), fat (49.7 ± 5.8g), protein (41.9 ± 4.8g; 0.8 g/kg), fiber (11.8 ± 2.1g) and sodium (1642.4 ± 298.6 mg) when compared to ultra-endurance nutrition recommendations. She was unable to complete the trail due to fatigue and anthropometric changes. By POST, she had decreased total mass (PRE: 53.5 kg vs POST: 48.4 kg), BMI (PRE 21.6 vs POST: 19.5), fat-free mass (PRE: 39.6 vs POST: 38.8), and body fat (PRE: 26% vs POST: 19.6%) when compared to PRE.

Conclusion

Trail-related challenges combined with high energy expenditures led to low nutrient intake which contributed to trail-ending injuries and performance decrements. Research aimed at addressing the barriers associated with thru-hike fueling is needed to identify nutritional opportunities to support hikers’ performance and reduce injury risks.

Keywords:

• Thru-hiking
• female athletes
• sports nutrition
• ultra-endurance
• sport performance

Introduction

Thru-hiking, or a multi-month, ultra-endurance journey, is an arduous sport that relies on both aerobic and anaerobic energy systems for extended periods (1). It elevates the stress and recovery demands beyond those observed in acute hiking events (2, 3). This is in part due to the multi-day, sequential stressors encountered such as the athlete’s requirement to carry all supporting materials such as food and water, sleeping materials, shelter, clothing, and recovery tools (4). These additional stressors require even higher energy, performance, and recovery considerations (2). Therefore, athletes need to prepare for the physical and mental tolls this unique type of athletic event places on an athlete and the increased recovery and resiliency demands required for a thru-hike journey.

The Pacific Crest Trail (PCT) is a popular thru-hike in North America. The number of long-distance hikers requesting permits (hikers traveling 805+ kilometers) issued yearly continues to rise with 7,852 issued in 2022 (5). This 4,265 kilometer (km) trail poses specific challenges to hikers due to its variable terrain, elevation changes, environmental conditions, and difficult path (6). The PCT starts at the Mexican border in southern California and spans up along the United States western coast, finishing in Canada. The trail sees an elevation change of 677, 341 km with the lowest point at 225 km in Oregon, and the highest point at 21, 168 km in California. Due to these variable terrains, there are several different climates throughout the trail, presenting several environmental challenges for thru-hikers (2).

In addition to weather, hikers must monitor food rations and water availability, making energy support and hydration (both fluid intake and electrolyte availability) a particular challenge. Water scarcity limits access to drinking water throughout the trail, particularly the southern regions such as southern California. Altitude and terrain changes have been known to increase respiratory water loss, ultimately raising fluid intake (7). This leads to increased load carriages to ensure enough food, clean water, and supplies to sustain the daily mileage to reach the next station (8). To properly prepare and accomplish a hike of this magnitude, performance nutrition must be carefully constructed to best support the athlete and reduce injuries and health concerns.

Understanding the energy demands, nutritional habits, and resulting performance outcomes surrounding this multi-month thru-hike is paramount to providing evidence-supported and sport-specific nutritional recommendations. However, to date, there are little data detailing energy demands, nutritional planning, or performance outcomes associated with thru-hikes, especially among female hikers (8, 9). The few works that are available are primarily male-focused case studies (2, 10). These studies have highlighted key themes of food-related challenges, anthropometric, and performance considerations but are lacking on how this information extends into female-athlete physiology. Women are severely underrepresented in this body of literature (8) despite a well-documented difference in their energy metabolism, physiology, and self-reported measurements during ultra-endurance events as compared to men (11).

In addition to understanding the exercise metabolism associated with thru-hiking, it is imperative to explore the correct assessment tools and experimental designs that best suit this unique field-based research. To date, research in these areas have focused on pre and post assessments. It is important to also capture data during the hike since nuances such as environmental conditions, terrain changes, and additional stressors further impact energy expenditure and subsequent nutritional needs. While it is ideal to investigate health and performance in larger cohorts, thru-hiking research feasibility questions remain, such sport-specific tools that have the capability, validity and sustainability to capture data in remote areas while still being light-weight enough to minimize additional load and stress on thru-hikers. These remaining questions lend themselves to begin researching more dynamic thru-hiking events through smaller, case-study, field-based models before expanding to larger, more robust experimental designs. For this reason, our research team focused on a case-study where we could collect more frequent self-reported and performance data as well as pilot non-intrusive data collection methods during the hike. Our goal was to identify key nutrition and performance barriers and gaps in the literature through this case study that could be investigated further in a larger cohort study with more specific hypotheses.

Therefore, this case study’s purpose was to quantify energy intake vs energy expenditure during a highly-trained, female thru-hiker’s trek through the PCT and assess its relationship to performance and health.

Methods

This case study followed a highly trained, female thru-hiker (Age (yrs): 62, Ht (cm): 157, Wt (kg): 53.5, BMI (kg/m²): 21.7, %BF: 26.0) as she embarked on a four-month hike on the PCT. Before beginning the case study, the athlete was provided with verbal and written explanation of the experimental design after which she provided written informed consent approved by the university’s Institutional Review Board (JU Project 2021-020). Following the thru-hike, the athlete read and approved the final manuscript for this publication.

This well-trained female thru-hiker had a history of long-distance hiking. Her experience included hiking the Florida trail (966 km), Appalachian Trail (805 km), East Coast trail (Newfoundland; 322 km), and Colorado Trail (580 km) and had completed the last three of these endeavors within the 3 years leading up to the PCT thru-hike. Her primary goal was to complete the PCT within the spring-summer months. While this was a longer thru-hike than her previous events, she organized her training and performance program to help support the extended time on trail. To prepare, she trained for 8 months before the start of the PCT thru-hike through sport-specific modalities, which included daily incline treadmill walking and light-weight and body weight-based, high-intensity, resistance training about three times per week. The athlete would also complete shorter, weekend or week-long hikes in the anticipated daily mileage of the PCT (∼32km/day) during this 8-month period. These training hikes allowed the athlete to test manageable load carriage weights and test different food and hydration tactics. Although much effort was put toward physically preparing for the hike, a limitation to the training program was that the athlete hiked in a primarily flat region, therefore there were minimal elevations, climbing-efforts, and variable environmental conditions to contend with. As with many thru-hikers and given the minimal information currently available, much of this work was self-monitored with anecdotal tips from the thru-hiking community as a guide (12).

Nutritionally, the athlete adhered to a lower-calorie, vegetarian diet. Of note, the athlete self-disclosed she battled with chronic disordered eating patterns (40+ years) and often followed a reward-food relationship (i.e., eat more if exercising, otherwise, limited, very low-caloric intake). Since nutrient-dense, vegetarian options are more challenging to come across during thru-hiking, she proactively shipped food crates to planned towns throughout the hike to have food ready for the next leg of the journey. The athlete self-disclosed she focused on calorie and nutrient dense food options to ship to each leg, knowing it would be more challenging to locate healthier, calorie and fat-dense, vegetarian-friendly options at rest stops.

Experimental design

The athlete tracked a 3-day diet record for dietary carbohydrate (CHO), fat (FAT), and protein (PRO) and completed body composition testing one week before (PRE) and after (POST) the thru-hike. On the morning of testing, the athlete was checked for euhydration (USG < 1.025), using a urine-specific gravity via a refractometer. Height (cm) was collected during the PRE visit only and measured on the same stadiometer three times and averaged to the nearest 0.01 cm. Body mass (kg) (Health O Meter 349KLX Digital Scale, Pelstar®, LLC, McCook, IL) was collected twice and averaged to the nearest 0.01 kg. Body composition was assessed via bioelectrical impedance using the Inbody 570 (InBody, Cerritos, CA) following the manufacturer’s guidelines.

During the hike, diet tracking was conducted via a web-based, end-to-end security-built application, Nutracheck (version 9.20.0, Nottingham, England). Performance data was tracked via the GPS, smartwatch, Garmin Instinct Solar Fitness Watch (Garmin Ltd, Olathe, Kansas). The athlete completed a web-based, self-report, wellness survey (WS) via Qualtrics each time she reached a town. The WS was answered on a 5-point Likert scale (1= Strongly agree; 5= Strongly disagree). Town stops were estimated to occur every 2-5 days throughout the hike and were primarily designed to restock supplies, connect to Wi-Fi, and provide a short respite.

Data were analyzed for descriptive (weekly averages, means ± SD) and frequency statistics. Statistical analysis was performed using GraphPad Prism 6.01 for Windows 10.

Results

The athlete began her hike on March 30th at the southern border and finished on June 8th, 2021 in Mammoth, CA after about ∼10 wk. She hiked for 70 days, culminating in a total of 1,506.35 km (∼ 26.1 ± 3.2 km/day over ∼7.58 ± 1.02 h/day). She planned to complete the entire 4,265-kilometers of the PCT but ultimately, stopped hiking early due to fatigue and anthropometric changes.

Thru-hike performance

The athlete was in a chronic calorie deficit throughout the thru-hike (Figure 1A). Her estimated energy expenditure was ∼2633.8 ± 428 kcal/day (range: 1968-2929 kcal/day). Comparatively, she recorded a low-calorie intake of 1285.3 ± 103 kcal/day (range: 1147-1438 kcal/day), leading to ∼1349 ± 428 kcal/day deficit throughout the hike. When compared to the estimated energy expenditure, the lower caloric intake amounted to a ∼13,485 kcal total deficit by the end of the thru-hike (Figure 1B).

Figure 1. A-B Weekly caloric expenditure, intake & deficit.

Daily averages, by week, of both energy expenditure as well as total caloric intake. Examining both elucidates a large mismatch in energy needs and intake that takes place over the course of the hike (A). Throughout the hike, as energy expenditure far outpaces energy intake, the chronic calorie deficit accumulated to ∼13,485kcal (B).

When compared to current ultra-endurance single-stage ultra-endurance nutrition recommendations (13), the athlete was under-consuming dietary CHO (169.5 ± 19.5g; range 150-200 g/day; 3.2 g/kg), FAT (49.7 ± 5.8g; range: 44-60 g/day), PRO (41.9 ± 4.8g; range: 36-53 g/day; 0.8 g/kg/day), fiber (11.8 ± 2.1g) and Na (1642.4 ± 298.6 mg) throughout the entire hike (Figure 2A–C).

Figure 2. A-C: Weekly macronutrient intake vs. dietary recommendations.

When compared to current ultra-endurance single stage ultra-endurance nutrition recommendations, the athlete was found to be under consuming fat (A), carbohydrate (B), and protein (C) throughout the hike. While not a perfect nutrition recommendation to compare to since thru-hiking is a slightly different athletic event, it highlights the chronic impact of low calorie, and low nutrient, intake over the course of the thru-hike.

The athlete completed ∼2-3 WSs/week. Compared to the first half of the hike, the athlete increasingly reported “disagree” or “strongly disagree” feeling satiated by the foods consumed, feeling well-hydrated, having restful sleep, and feeling recovered during the second half of the hike. However, she continued to respond with “agree” or “strongly agree” to feeling mentally sharp and motivated throughout.

PRE vs post thru-hike

Although the athlete habitually consumed a low-calorie diet (PRE: 915 ± 323 kcal/day vs POST: 1026 ± 514 kcal/day), the thru-hike further intensified her ability to maintain body mass, including fat-free mass. Compared to PRE, the athlete had decreased total mass (PRE: 53.5 kg vs POST: 48.4 kg), BMI (PRE: 21.6 vs POST: 19.5), fat-free mass (PRE: 39.6 vs POST: 38.8), and body fat (PRE: 26% vs POST: 19.6%) while total body water was maintained (PRE: 28.9 L vs POST: 28.3 L) (Figure 3A and B) by the end of the hike.

Figure 3. A-B: P and post-hike anthropomorphic measurements.

Compared to before the start of the hike (PRE), the athlete had a decrease in percent body fat (A) and fat free mass (B) by the end of the hike (POST).

Discussion

This case study’s purpose was to quantify energy intake vs energy expenditure during a female thru-hikers trek and assess its relationship to performance and health. The main findings revealed 1) low energy (LE) intake combined with high energy expenditure led to the athlete being in a chronic calorie deficit 2) the chronic calorie deficit negatively impacted performance and anthropometric/body composition changes, and, an unexpected finding included 3) how habits and symptoms associated with relative energy deficiency in sport (REDs) may present themselves in highly trained, Masters class athletes, an area of research severely under-reported and discussed.

Inadequate nutritional intake could lead to large losses in fat-free mass, detriments in mental statuses of recovery, and hiking performance, as measured in this case study. By POST, the athlete, who began the hike in a naturally lean state, had lost ∼10% of her body weight and ∼6.5% of body fat. Moreover, this loss and associated fatigue led to a premature hike end. The athlete self-selected to stop the hike due to observed performance decrements (i.e., slower pace, higher fall risks, etc.) and for fear of short and long-term health issues. Some weight loss has been reported with thru-hiking (14) but this athlete also reported increased fatigue and decreased sleep quality and recovery. This signals a lack of energy availability and nutrient support and may lead to compromising the musculoskeletal integrity and potentially downstream, overuse injuries.

Several compounding factors contributed to the chronic calorie deficit during thru-hiking. These barriers included the impact of hiking logistics in general (i.e., food weight, food safety concerns, etc.), food access (both on the hike and during town stops), access to nutritionally dense and variable foods, budgetary considerations, food planning issues (i.e., shipping issues, damage during transportation, etc.), palatability of prepackaged/planned foods, and food source fatigue. These, combined with hiking and environmental stressors exacerbated the chronic LE intake. The athlete’s diet records demonstrated these challenges such as a shift to easier-to-carry options and a decrease in nutrient-dense options, fresh and whole foods, and food and nutrient variety from PRE to during the hike. Each of these contributed to the lower calorie and reduced nutrient intake she reported. It is important to note this was/is a highly experienced, well-trained thru-hiker so these challenges can affect any thru-hiker, regardless of training age. If energy needs are not met, the body may face nutrient deficiencies during a remote-athletic endeavor, potentially at a rapid rate, as observed in this case study, with the possibility of malnutrition and downstream physiologically deleterious effects.

This highlights the importance of and need for more performance team personnel in outdoor athletic event, such as thru-hiking. One study focused on high-altitude climbers found that despite having trouble managing nutrient needs and caloric intake, a mere 7% of climbers connected with a dietician before an excursion (15). Like our study, climbers consistently struggled with maintaining body weight, body fat, and lean mass during multi-day and multi-month climbs (15). RDs and strength and conditioning (S&C) specialists have a much-needed role for thru-hikers and could aid in more positive outcomes related to body composition, performance, and overall health. RDs could play a pivotal role in thru-hiking by providing counseling, estimated nutrient needs, nutrient-related testing, create sport-specific meal programs, and arrange product ordering and shipping schedules. Our team of sports dieticians (RDs) created an example of how some of this athlete’s food options could have been improved to address some of the challenges she faced during the thru-hike, emphasizing the role of RDs for this sport and the need to connect more with these athletes (Table 1). A previous case-study found a handcycling ultra-endurance male athlete improved his performance after participating in a 30-week muscular strength and endurance-focused training program (16). Similarly, S&C specialists can be instrumental in designing hiking-specific training programs to support the physical demands needed to complete a thru-hike, reduce injury rates throughout the journey, and improve recovery strategies during and after thru-hiking events.

Table 1. PRE and during hike 24-hour diet record vs an “Sample Ideal” 24 h-sample menu: The athlete’s 24-h diet records PRE and during the hike demonstrated consistent food intake, however, it was below target calorie ranges. Additionally, it highlighted food challenges many thru-hikers face such as decreased nutrient density, fresh/whole food options, and food variety. The sample diet record adds food options to increase calories, nutrients, and variety while remaining hiking-friendly.

	Pre-hike	During hike	Sample ideal
Breakfast	Waffle, Fruit, and Coffee	Poptart, CIB, Coffee	WP, Poptart, Dried Fruit, Coffee
	1 Eggo low fat waffle w/	1/3 Poptart	20 g protein powder
	1 Tbsp peanut butter	1 pkt CIB	1 Poptart
	5 large strawberries	½ srv nonfat DMP	40 g dried bananas
	Coffee w/ ½ cup milk	1 tsp instant coffee	1 Tbsp peanut butter
			1 tsp instant coffee
Totals	231 cals, 6 g PRO, 32 g CHO, 10 g FAT, 2.5 g FIBER, 249 mg Na	243 cals, 9.8 g PRO, 46 g CHO, 2 g FAT, 1 g FIBER, 244 mg Na	433 cals, 24 g PRO, 72.5 g CHO, 6 g FAT, 3 g FIBER, 265 mg Na
Lunch	English Muffin Sandwich	Chips and Trail Mix	WP, Trail Mix, Liquid IV
	1 slice cheddar cheese	1/4 snack bag Cheetos	20 g protein powder
	2 slices tomato	½ cup Cape Cod trail mix	½ cup Cape Cod trail mix
	2 leaves lettuce		35 g dried pineapple
	1 Tbsp mayo		½ pkt Liquid IV
	1 medium apple
Totals	234 cals, 11 g PRO, 47 g CHO, 2.5 g FAT, 5 g FIBER, 606 mg Na	340 cals, 8.5 g. PRO, 28 g CHO, 22.5 g FAT, 4 g FIBER, 107 mg Na	589 cals, 27 g PRO, 84 g CHO, 17 g FAT, 6.5 g FIBER, 503 mg Na
Dinner	Sushi	Mac & Cheese, Oreos	Mac & Cheese, Harvest Snaps
	4 pieces tuna roll	½ pkg Mountain House (MH) freeze dried mac & cheese	1 pkg MH freeze dried mac & cheese
	4 pieces rainbow roll	1 ½ golden oreos	30 g Harvest Snap baked peas
	3 pieces tempura roll
	3 pieces California roll
Totals	706 cals, 32.5 g PRO, 108 g CHO, 14.5 g FAT, 5.5 g FIBER, 1217 mg Na	555 cals, 21.5 g PRO, 60 g CHO, 25.5 g FAT, 1 g FIBER, 1318 mg Na	756 cals, 31 g PRO, 80 g CHO, 35 g FAT, 6 g FIBER, 1458 mg Na
Snacks	1 cup green grapes		¼ cup Skittles
			3 Golden Oreos
			1 snack back Cheetos
			1 Performance Energy Gel
Totals	90 cals, 1.5 g PRO, 21 g CHO, 0 g FAT, 1.5 g FIBER, 0 mg Na		590 cals, 3 g PRO, 102 g CHO, 19 g FAT, 0.5 g FIBER, 575 mg Na
Daily Total	1261 cals, 51 g PRO, 208 g CHO, 27 g FAT, 14.5 g FIBER, 2072 mg Na	1138 cals, 40 g PRO, 134 g CHO, 50 g FAT, 6 g FIBER, 1669 mg Na	2368 cals, 85 g PRO, 338 g CHO, 77 g FAT, 16 g FIBER, 2850 mg Na

* CIB: Carnation Instant Breakfast; DMP: dry milk powder; WP: whey protein.

Sample Ideal: uses foods similar to what hiker used, but in portions to better meet needs.

Environmental conditions were another compounding factor on the negative energy balance observed in this study. Although not directly measured, the extreme temperature ranges the athlete faced may have played a role in energy expenditures and food and water restock considerations. Using the athlete’s self-tracking logs and the National Weather Service, National Oceanic and Atmospheric Administration (NOAA) weather reports, temperatures during the 2021 thru-hike season ranged from -1^C to 32^C. Much of the temperature was dependent on elevation. For example, certain desert sections at the start of the hike also had mountain ranges above 3048 meters (m) which resulted in wide ranges of temperatures during the first 1127 km. Higher elevations were also found to have more variable precipitation, during which the athlete reported encountering hail, snow, and high winds. Environmental conditions, particularly altitude and temperature changes, greatly impact caloric and hydration needs in ultra-endurance sports and if ignored, these deficits could increase injury and illness rates (17). Thru-hiking is already a high caloric need sport; the additional extreme environmental conditions stress energy needs even further and must be considered when building nutrition and hydration programs for these athletes.

Perhaps one of the more revealing aspects of this study was how chronic disordered eating may present itself later in an athlete’s life. This athlete revealed a 40+ year history of disordered eating that primarily manifested itself as a very low-calorie and restrictive food choice diet. Eating disorders can impact any athlete in any sport regardless of sex, gender, age, or competition level (18). There is an abundance of research on disordered eating in younger female athletes (<25 yr) (18) and while there is a growing number of studies on eating disorders amongst older women (∼3.5%) (19, 20), to date, there is minimal research on disordered eating in Master class female athletes. More research is needed to better understand how older athletes with a history of disordered eating continue to manage the challenges faced and what types of tools and approaches can be offered to help these athletes.

Chronic LE, be it from high energy expenditures and/or lower calorie intakes, may lead to a series of health and performance deficits, collectively known as Relative Energy Deficiency in Sport (RED-S). It is important to note that RED-S is not always tied to disordered eating but those with a history of disordered eating tend to be at a higher risk for developing this syndrome (18). Older athletes with chronic cases of low energy availability (LEA) develop more negative consequences (21) that manifest themselves as decreased fat-free mass, bone mineral density, and hematological stores, and alter a myriad of hormones including those that impact basal metabolic rate, hunger and satiety, reproductive health, stress, and inflammation (22, 23). These alterations can lead to physical and psychological detriments, especially as the length of time under LE conditions persists with aging (24).

Despite the chronic LE, the WS did not indicate that the athlete was experiencing all of the noted potential performance consequences of RED-S such as depression, irritability, or decreased concentration (22), calling attention to the unique way RED-S expresses itself in individuals and how it may present in different types of sports. In fact, the athlete self-reported feeling mentally sharp and motivated throughout the thru-hike even while responding with increased notes of feeling less satiated, hydrated, and recovered as the hike continued. This is reflected in previous works on ultra-endurance sports where these athletes tend to demonstrate higher levels of “mental toughness” and psychological resiliency compared to other sports (25). This sport-characteristic provides valuable insight for those screening for RED-S and emphasizes exploring RED-S in more sport-specific manners. To date, RED-S screening tools and general guidance are geared toward younger athletes. Future investigations should explore how RED-S manifests itself in Master class athletes, the sports these athletes may be engaging in, and how current tools/approaches to address RED-S could be best adapted and personalized for athletes across the lifespan.

Future research opportunities

Thru-hiking has increased in popularity and the PCT is in the top three most frequented trails in the United States (2). The outcomes of this study can be translated to the growing, thru-hiking audience by bringing forth awareness of the exuberant energy expenditures observed and how the combination of environmental conditions and nutrient imbalances impact energy, muscle repair, cellular function, and overall health and performance. The protocol lends itself to a larger-scale study to continue learning more about the role of nutrition and exercise training on thru-hiking performance and health considerations and provides a framework for future thru-hiking research. Much of this research could focus on the identified challenges from this and other studies, such as maintaining weight and muscle mass, improving recovery strategies, and reducing injuries and illnesses. Future research could look at larger groups and the impact of nutritional interventions, both in caloric manipulation as well as nutrient profile, to identify strategies to address the nutrient needs, challenges, and barriers observed. Specific biomarkers could be targeted to learn more about how thru-hiking impacts other aspects of performance physiology such as stress profiles, cognitive functioning, endocrine responses, inflammation and immune markers, and metabolic health. Further investigations on sex-differences on energy balance and performance could provide insight into the divergent energy metabolisms noted in previous works, how this translates to thru-hiking, and the impact of hormonal and age-related factors on this paradigm. Finally, exploring how wearables and other technologies can be implemented into this work could provide much-needed insight into real-time, field-based data. This work is instrumental in building more targeted nutrition and training programs to support thru-hiker’s health, performance, and recovery systems. Overall, while the focus of this study was thru-hiking, it has several tenets that relate to broader audiences that are stationed in outdoor, extreme environments for extended periods of time, such as other ultra-endurance sports and tactical athletes. The outcomes of this study provide insight into how these strenuous conditions may impact energy balance and how this extends into acute and chronic health and performance parameters in female athletes.

Conclusion

In this case study, LE led to decreased performance, body composition, and energy in a well-trained, Master class, female thru-hiker. This study underscores the critical need for adequate energy intake during thru-hiking, ultra-endurance athletic events, especially those with challenging environmental stressors. It also strongly supports the need for multidisciplinary approaches for optimizing performance and reducing injury risks in ultra-endurance female athletes.

There are several gaps in the literature remaining, particularly how LEA, and possibly RED-S, expresses itself in Master class athletes. Adequate energy intake is paramount to a successful thru-hike and more research, and robust assessments, on energy needs, sustainable and enjoyable dietary approaches, and optimal thru-hike-specific dietary counseling can provide much-needed insight into ways to reduce injury risks and support performance and recovery in thru-hiking athletes.

Authorship

CS contributed to the concept, design, data collection, data analysis, and drafting manuscripts. LL and JR contributed to the concept, design, data collection, data, and analysis. AJ contributed to data collection and data analysis. MC and KS contributed to data analysis and figure/table creation. All authors contributed to manuscript writing, critical evaluation of the intellectual content, and article approval.

Acknowledgments

We are grateful to the exercise science research team and all members of Jacksonville University’s academic technology team who volunteered time and support for this research project. We are especially grateful to our participant who volunteered their time and provided insight into their health and performance throughout a very special hike and athletic endeavor.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The study was partially funded by The Office of Research & Sponsored Programs through the Summer of Scholarship Faculty Grant at Jacksonville University.