Effects of Trail Running versus Road Running—Effects on Neuromuscular and Endurance Performance—A Two Arm Randomized Controlled Study

g on less predictable terrain has the potential to increase the stimulation of the neuromuscular system and can boost aerobic performance. Hence, the purpose of this study was to analyze the effects of trail versus road running on neuromuscular and endurance performance parameters in running novices. Twenty sedentary participants were randomly assigned to either a trail (TRAIL; n = 10) or road running (ROAD; n = 10) group. A supervised and progressive, moderate intensity, and work-load-matched 8 wk endurance running program on TRAIL or ROAD was prescribed (i.e., randomized). Static balance (BESS test), dynamic balance (Y-balance test), gait analysis (RehaGait test, with regard to stride time single task, stride length dual task, velocity single task), agility performance (t-test), isokinetic leg strength (BIODEX), and predicted VO 2max were assessed in pre- and post-tests. rANOVA analysis revealed no signi cant time–group interactions. Large effect sizes (Cohen's d) for pairwise comparison were found for TRAIL in the BESS test (d = 1.2) and predicted (pred) VO 2max (d = 0.95). Moderate effects were evident for ROAD in BESS (d = 0.5), stride

leg strength (BIODEX), and predicted VO 2max were assessed in pre- and post-tests. rANOVA analysis revealed no signi cant time–group interactions. Large effect sizes (Cohen's d) for pairwise comparison were found for TRAIL in the BESS test (d = 1.2) and predicted (pred) VO 2max (d = 0.95). Moderate effects were evident for ROAD in BESS (d = 0.5), stride time single task (d = 0.52), and VO 2max predicted (d = 0.53). Possible moderate to large effect sizes for stride length dual task (72%), velocity single task (64%), BESS test (60%), and the Y-balance test left stance (51%) in favor of TRAIL occurred. Collectively, the results suggested slightly more bene cial tendencies in favor of TRAIL. Additional research is needed to clearly elucidate differences between TRAIL and ROAD, not only in novices but also in experienced exercisers. Keywords: postural balance; gait; agility; muscle strength; long distance running; endurance training; running surface 1. Introduction Regular physical activity, such as running, enhances cardiorespiratory and neuromuscu- lar performance and is associated with a delay in all causes of mortality and morbidity [1–4]. Lee et al. [5] found that minimal running training volumes of 30–59 min a week, or5–10 mina day are associated with lower risks of all-cause and cardiovascular mortality. Despite proven health benefits of physical exercise, the number of sedentary people worldwide is large and steadily growing [6–8] in both sexes and with increasing age [7,9]. Physical inactivity acceler- ates aging-induced functional decrements and compromises physical performance which can lead to impairments in activities of daily living [ At approximately 30 years of age, muscle mass and muscle strength begin to decrease gradually by 10–15% each decade [3]. Progressive skeletal muscle atrophy is accompanied by a loss in muscle coordination and a decline in balance [11], which can already be evident in individuals of 40 years of age [12]. Balance impairments and related spatiotemporal gait de cits both represent crucial risk factors for falls and fall-related injuries [13–15]. Falls and fall-related injuries as well as general health impairments not only occur in Int. J. Environ. Res. Public Health2023,20, 4501.

a decline in balance [11], which can already be evident in individuals of 40 years of age [12]. Balance impairments and related spatiotemporal gait de cits both represent crucial risk factors for falls and fall-related injuries [13–15]. Falls and fall-related injuries as well as general health impairments not only occur in Int. J. Environ. Res. Public Health2023,20, 4501.

Int. J. Environ. Res. Public Health2023,20, 4501 2 of 14 the elderly but are a frequent problem in middle-aged and young people [16,17]. Few studies have investigated falls and the frequencies of falls in young and middle-aged individuals [16]. In a longitudinal study by Niino et al. [17], the prevalence of falls among middle-aged individuals (40–59 years) was 12.9%, compared to 16.5% among the elderly group (60–79 years). Talbot et al. [16] observed a prevalence of one or more reported falls within a two-year period in 18.5% of young adults, 21% of middle-aged adults and 35% of older adults. In addition to the direct consequences of falls,many people develop a fear of falling after such an event which often leads to a vicious cycle of reduced physical activity, decreased mobility and muscle strength, and a subsequent higher risk for future falls [14,18,19]. To refute the natural decline in neuromuscular properties with aging and augment spontaneous balance and maintenance of strength, our main study objective was to de- termine the effectiveness of exercising on uneven surfaces (i.e., dirt trails) vs. familiar (or predictably even road) surfaces in a younger adult population on the prior mentioned variables (e.g., neuromuscular or gait training, balance, strength). For instance, running has been shown to improve or amplify several task-speci c, metabolic, and neuromuscular factors [20]. However, few studies have focused on neuromuscular variables (e.g., gait parameters via a wearable gait analysis system) resulting from endurance training on distinctly different surfaces [20]. As a suggestion, future researchers should theoretically look at the protective effects of frequent running on uneven surfaces related to unexpected falls, especially in the elderly. Ultimately, the impact of trail running, which is attracting an increasing number of recreational and competitive runners [21,22], compared to road running, has not been extensively compared. In the present project, we hypothesized trail running would lead to more pronounced improvements in neuromuscular and endurance performance than road running. These assumptions are based on the different characteristics of surface type and gradients between the two conditions. Trail running tends to invoke higher challenges for the neuromus- cular system,

compared to road running, has not been extensively compared. In the present project, we hypothesized trail running would lead to more pronounced improvements in neuromuscular and endurance performance than road running. These assumptions are based on the different characteristics of surface type and gradients between the two conditions. Trail running tends to invoke higher challenges for the neuromus- cular system, especially regarding involved muscle coordination, proprioception, and activation [23–26] compared to road running. Furthermore, since uphill running is an effective stimulus for improving endurance running performance [27,28] and submaximal running economy [27,29] we expected a more pronounced performance at posttest in the submaximal incremental treadmill test for TRAIL. 2. Materials and Methods 2.1. Participants and Experimental Setting This pilot study adheres to CONSORT guidelines [30]. Participants were recruited via yers, posters, word-of-mouth, and local advertisement as well as via “batch” emails among faculty and staff at the university where the project was conducted. Inclusion criteria [31] for participation were: (i) 18–59 years of age; (ii) currently sedentary or not exercising more than twice a week for the last three months; (iii) free from any injury or illness and currently no intake of any medication; (iv) and non-smoker. Importantly, according to ACSM, sedentary, healthy (e.g., free of disease, non-smoker, uninjured) individuals will showcase a greater physiological change from pre to post exercise intervention. To ensure that participants met the inclusion criteria, all subjects were asked to complete several physical activity questionnaires. The questionnaires included: (a) International Physi- cal Activity Questionnaire—Short Form (IPAQ-SF) [32], (b) the Physical Activity Readiness Questionnaire (PAR-Q&YOU) [33], and the (c) American College of Sports Medicine (ACSM) Risk Stratification [31] to assess individual current health and activity levels. If a participant reported two risk factors related to cardiovascular diseases, he/she had to consult a physician for medical clearance to participate in moderate to vigorous exercise. The study was conducted according to the Code of Ethics for Human Experimentation of the World Medical Association and the Declaration of Helsinki [34]. Participants were informed in detail about the design of the study, including the potential risks and bene ts of

diseases, he/she had to consult a physician for medical clearance to participate in moderate to vigorous exercise. The study was conducted according to the Code of Ethics for Human Experimentation of the World Medical Association and the Declaration of Helsinki [34]. Participants were informed in detail about the design of the study, including the potential risks and bene ts of included procedures, before providing their informed written consent to participate. The study protocol was approved by the Institutional Review Board of the Northern Michigan

Int. J. Environ. Res. Public Health2023,20, 4501 3 of 14 University (Trial registration number: ID Proposal Number HS16-786; Date of registration: September, 2017). Participants were anonymously assigned by the researcher via simple randomization using a random number generator to either TRAIL (n = 20) or ROAD (n = 19) and entered into an endurance exercise program. The program consisted of 8 weeks of gradually increasing running workouts with a total amount of 29 training sessions. This randomized controlled pilot trial compared two training groups (i.e., TRAIL vs. ROAD) in terms of balance, gait, agility, along with strength and endurance performance measures in a pre- and post-intervention testing format. Participants in the TRAIL group ran outdoors on uneven and soft trails with varying gradients and under-foot terrain (e.g., rocks, roots, more consistent undulating routes). Participants from the ROAD group ran on predictable terrain or roads with asphalt, concrete or paved surfaces exhibiting no or infrequent gradients. An adherence rate of a minimum of 80% (24 runs) was required for inclusion in the nal analysis. To con rm, a total of 39 healthy adults were initially assigned, whereof 6 subjects did not start the program; 5 participants dropped out during the intervention due to injuries; 3 participants did not meet the required 80% adherence rate and 1 participant was not available for post testing. Additionally, 2 participants (i.e., “4” total) from each group were excluded from analysis due to other exclusion criteria—not following the prescribed training load and for participating in additional training during the period of the study. Then end total of analyzed participants equaled 20. Demographic data at baseline for all participants who received the allocated interven- tion are depicted in Table. Table 1.Demographic data at baseline. TRAIL 1 (n = 10, 6 fem) ROAD 1 (n = 10, 7 fem) Total (n = 20) Female/male (n) 6/4 7/3 13/7 Age (years) 33.2 6.8 29 10.5 31.3 8.8 Height (cm) 171.1 8.0 170.9 6.6 171 7.3 Weight (kg) 77.4 17.6 74.5 15.6 76.1 16.5 BMI (kg/m 2 ) 26.2 4.1 25.4 4.5 25.8 4.3 Physical Activity (min/week) 1904.8 957.5 2105.3

= 10, 6 fem) ROAD 1 (n = 10, 7 fem) Total (n = 20) Female/male (n) 6/4 7/3 13/7 Age (years) 33.2 6.8 29 10.5 31.3 8.8 Height (cm) 171.1 8.0 170.9 6.6 171 7.3 Weight (kg) 77.4 17.6 74.5 15.6 76.1 16.5 BMI (kg/m 2 ) 26.2 4.1 25.4 4.5 25.8 4.3 Physical Activity (min/week) 1904.8 957.5 2105.3 1679.5 2000.5 1445.6 1 Values are mean ( SD). TRAIL = trail running group. ROAD = road running group. 2.2. Experimental Design Qualifying participants were asked to report to an Exercise Science Laboratory for pre- and post-intervention testing. Post-testing sessions were scheduled at a similar time of the day as pre-testing and within a week upon completion of the training program in November and December 2017, depending on pre-testing dates. Testing order, as well as the examiner were kept constant for each participant. Finally, ten participants in each group were included in the statistical analysis. The study ow is depicted following the CONSORT criteria, which is easily referenced [30]. Notably, 10 participants in each group provided signi cant differences (alpha error proba- bility: 0.05) and notable study power (i.e., 1-beta error probability: 0.9) when moderate to large effects size differences between group were presumed for balance performance as the primary outcome. Lastly, mandatory running meetings were held twice a week and coaching appoint- ments were scheduled as required. Furthermore, participants were contacted by email or phone once a week for feedback. As an additional motivation, a nal joint 5k running event was held upon completion of the intervention.

Int. J. Environ. Res. Public Health2023,20, 4501 4 of 14 2.3. Heart Rate and Blood Pressure Prior to baseline testing, a blood pressure cuff (Adcuff™, Hauppauge, NY, USA) and stethoscope (Littmann, St. Paul, MN, USA) were employed for blood pressure measures; then, pre-exercise resting heart rate (Polar monitor and watch, Lake Success, NY, USA), as well as body height (Seca stadiometer, Chino, CA, USA) and weight (Health O Meter scale, Mccook, IL, USA) were measured. Maximal heart rate (HRmax) in beats per minute (bpm) was predicted using the following formula according to Tanaka et al. [35]: 207—(age 0.7) for men and 206—(age 0.88) for women. The lateral preference inventory for measurements of footedness [36] was used to evaluate leg dominance. Limb length was measured from the umbilicus to the medial malleolus of the right leg using a tape measure [37]. Blood pressure, pre-exercise resting heart rate, as well as body height and weight measurements were repeated before post-testing as well. 2.4. Warm-Up Warm-up consisted of walking on a treadmill for 5 min at a rate of perceived exertion (RPE) of 3 on the Borg CR-10 scale [38], followed by dynamic stretching and muscle activation (Knee Hug to Forward Lunge–Elbow to Instep, Heel to Butt Moving Forward with Arm Reach, Handwalk, Lateral Squat Low). 2.5. Static Balance Testing Static balance was tested with the Balance Error Scoring System (BESS) [39], which evaluates 3 stance variations in the following order: (1) double leg, (2) single leg, and (3) tandem or feet in line with one another. The test takes place on 2 different surfaces, starting on rm for all “3” conditions and ending on foam for all “3” conditions while wearing no shoes. Each trial lasts 20 s, during which the number of deviations from the proper testing position were counted. Deviations from the proper testing position in the BESS test are: (a) moving hands off the hips; (b) opening the eyes; (c) step, stumble or fall; (d) abduction or exion of the hip beyond 30 ; (e) lifting the forefoot or the heel off of the testing surface; and (f) remaining

of deviations from the proper testing position were counted. Deviations from the proper testing position in the BESS test are: (a) moving hands off the hips; (b) opening the eyes; (c) step, stumble or fall; (d) abduction or exion of the hip beyond 30 ; (e) lifting the forefoot or the heel off of the testing surface; and (f) remaining out of proper testing position for more than 5 s. Proper position consists of the hands on the iliac crest, eyes closed, and consistent foot position. For the double leg stance, feet need to touch and remain at on the testing surface. For the single leg stance, the participant stands on the non-dominant leg with the other leg held in approximately 20 of hip exion, 45 of knee exion, and neutral position in the frontal plane. For the tandem stance, one foot is placed in front of the other with the heel of the anterior foot touching the toes of the posterior foot, and the non-dominant leg in the posterior position. The maximum amount of errors for any single condition was set at 10. If multiple errors were committed simultaneously, only one was recorded. To improve reliability, the test was repeated 3 times by the same examiner [39] and the mean score of the three trials was calculated for nal analysis. 2.6. Dynamic Balance Testing The Y Balance test (YBT) was performed to evaluate dynamic postural stability and functional symmetry during single leg stance in three (anterior, posteromedial, posterolateral) directions [40]. In a Y pattern, each posterior line was marked with tape 135 from the anterior line and 90 apart from one another. Subjects performed a practice trial followed by three test trials for each direction and each leg and were instructed to reach as far as possible, thereby pushing a pen held by the examiner to mark the reaching distance. The testing order started with standing on the left foot and reaching in the anterior direction followed by the trials standing on the right foot for the same direction. This procedure was repeated for all directions. Trials were considered

were instructed to reach as far as possible, thereby pushing a pen held by the examiner to mark the reaching distance. The testing order started with standing on the left foot and reaching in the anterior direction followed by the trials standing on the right foot for the same direction. This procedure was repeated for all directions. Trials were considered invalid and were repeated if the participant either made a heavy touch or rested the reaching foot on the ground, could not return in a controlled way to the starting position, raised or moved the stance foot, or kicked the marker with the

Int. J. Environ. Res. Public Health2023,20, 4501 5 of 14 reaching foot to gain more distance [40]. Results were calculated as a composite score with the help of following formula: (((anterior length + posteromedial length + posterolateral length)/3 leg length) 100). (1) 2.7. Gait Analysis Spatiotemporal gait parameters (stride time [s], stride length [m], and stride velocity [m/s]) were measured during 20 m (65.6 feet) of level walking at self-selected habitual walking speed by using the portable gait analysis system RehaGait ® (Hasomed GmbH, Magdeburg, Germany). The RehaGait ® system consists of two mobile sensors which are attached to the lateral part of each shoe to measure linear acceleration, angular velocity, and the magnetic eld of the foot at a sampling rate of 500 Hz [41]. Each participant performed a familiarization trial followed by 2 trials with single task condition and 2 trials with dual task condition. For dual task trials, participants were asked to perform a double-digit subtraction task while walking. The combination of gait analysis with cognitive interference tasks was applied to distract participants and limit the cognitive resources for gait control. The mean score for each condition was included in further analysis. For all trials, the phases of gait initiation and deceleration at the end of the walkway were excluded from analysis. For both pre- and post-testing, participants were wearing their running shoes. 2.8. Agility Testing Thet-test evaluates the subjects' agility, leg power and leg speed [42]. Four cones are set out in a T pattern. The test starts at the rst cone with a forward sprint of 9.14 m to the second cone, continues with shuf ing sideways for 4.57 m to another cone on the right, then 9.14 m to the one on the left, and again 4.57 m back to the middle, before ultimately running backwards 9.14 m to return to the starting point. The base of the cone always has to be touched with the hand further away from the cone when performing the test. The fastest out of 3 trials was used for analysis. 2.9. Strength Testing Unilateral isokinetic concentric leg strength

This study analyzes the effects of trail versus road running on neuromuscular and endurance performance in running novices.