Do Highly Trained Mountain Runners Differ from Recreational Active Non-Runners on Range of Motion and Strength in the Hip and Ankle as Well as Postural Control?

governing mountain running force athletes to implement into their training programmes uphill and downhill running on unstable surfaces, which are demanding for hip and ankle as well as for the postural control system. The aim of the present cross-sectional study was to compare highly trained mountain runners (MR) and recreational active non-runners (NR) on range of motion (ROM) and strength in the hip and ankle, as well as dynamic postural control. Thirty MR and thirty-two NR were included in the study. ROM was assessed using a digital inclinometer. Strength was measured using a hand-held dynamometer. Postural control was evaluated using the lower quarter Y-balance test (YBT-LQ). The results showed that MR, in relation to NR, had statistically signi cant smaller hip external rotation

and ankle, as well as dynamic postural control. Thirty MR and thirty-two NR were included in the study. ROM was assessed using a digital inclinometer. Strength was measured using a hand-held dynamometer. Postural control was evaluated using the lower quarter Y-balance test (YBT-LQ). The results showed that MR, in relation to NR, had statistically signi cant smaller hip external rotation ROM (p= 0.007), lower hip external rotator (p= 0.006) and extensor (p= 0.023) strength and greater normalised anterior reach in the YBT-LQ (p= 0.028). Mountain running training may reduce hip external rotation ROM as well as hip external rotator and extensor strength. Moreover, such training may improve postural control. MR should implement exercises targeted at developing hip ROM and strength. Furthermore, it seems that mountain running training may be a good way to improve postural control. Keywords:mountain running training; strength; range of motion; dynamic postural control 1. Introduction Running is very common form of physical activity around the world, as demon- strated, for example, by the 15.5 million U.S. races completed in 2012 [1] and approximately 50 millionpeople who are frequent long-distance runners in Europe [2]. Regular running provides numerous health bene ts such as reduced total cardiovascular, cancer, neurologi- cal and infectious mortality [3], as well as reduced weight gain [4] and risk of cardiovascular disease [5]. However, inappropriate administration of this form of physical activity may lead to negative consequences, e.g., running-related injuries (RRI). In a meta-analysis performed by Videbæk et al. [6], it has been demonstrated that, depending on the type of runner, injury de nition and length of follow-up, RRI incidence rate ranges from 2.5 to 33.0 per 1000 h of running. It should also be borne in mind that the consequences of each injury are dif culties participating in normal training and competition [7], as well as socio-economic costs [8]. One type of running, which has especially grown in popularity in recent years, is mountain running [9]. The discipline of mountain running takes place on various types of natural terrain (e.g., sand, dirt roads, forest, paths, single-track footpaths, snow), and in J. Clin. Med.2023,12, 2715.

dif culties participating in normal training and competition [7], as well as socio-economic costs [8]. One type of running, which has especially grown in popularity in recent years, is mountain running [9]. The discipline of mountain running takes place on various types of natural terrain (e.g., sand, dirt roads, forest, paths, single-track footpaths, snow), and in J. Clin. Med.2023,12, 2715.

J. Clin. Med.2023,12, 2715 2 of 10 various kinds of environments (e.g., mountains, forests, plains, deserts). Mountain races are traditionally divided into “uphill” and “up and down” types. The average altitude gain or loss can vary from 50 m to 250 m per kilometre, and a distance up to42.2 km [10] . Those rules force athletes to implement high-volume discipline-speci c exercises into their training programmes, such as uphill (UR) and downhill (DR) running, often on various unstable surfaces, which are generally very demanding on the human body. UR and DR are different from level running (LR) with regard to movement biomechanics (i.e., foot strike pattern, ground reaction forces, joint kinematics and kinetics, as well as shock impact); therefore, they may result in speci c training-induced musculoskeletal system disfunctions [11]. The most common injuries sustained by long-distance runners were found to be Patellofemoral Pain Syndrome (PFPS), Achilles Tendinopathy, Iliotibial Band Syndrome (ITBS) and Medial Tibial Stress Syndrome (MTS) [12–14]. Moreover, mountain running is very strenuous with regard to an athlete's postural control system due to the presence of an unstable ground combination (after which runners must run with considerable speed) and exercise-induced fatigue, which deteriorates balance [15]. Advanced specialist sport training may cause changes in muscle strength [16,17], joint range of motion (ROM) [18,19] and dynamic postural control [20,21]. On the one hand, these changes are necessary to improve performance; on the other, they may lead to dysfunction associated with RRI. Assessment of the listed variables may be performed using reliable, valid, inexpensive, portable and easy-to-use tools in a clinical setting. Hand-held dynamometers (HHD) are convenient and versatile devices used for muscle strength testing. A HHD can be placed between the hand of the practitioner and the athletes' tested body part, similar to how a practitioner would perform a manual muscle test. Unlike manual muscle testing, HHD provides a quanti ed measurement of force [22]. Digital inclinometers (DI) are one of the tools used to assess ROM in the joints. The DI is an instrument applied to measure surface inclination (in degrees) by sensors sensitive to gravity. One of the

part, similar to how a practitioner would perform a manual muscle test. Unlike manual muscle testing, HHD provides a quanti ed measurement of force [22]. Digital inclinometers (DI) are one of the tools used to assess ROM in the joints. The DI is an instrument applied to measure surface inclination (in degrees) by sensors sensitive to gravity. One of the signi cant advantages of DI in ROM measurements is that its positioning does not depend that much on anatomic references [23]. The lower quarter Y-balance test (YBT-LQ) is used to evaluate dynamic postural control. YBT-LQ is popular and extensively utilised for injury risk identi cation, return-to-sport testing and pre–post-intervention measurements [24]. Based on a systematic review performed by Francis et al., [14] it seems that the foot/ankle is second most frequently injured area among runners. In turn, the hip holds just fth place in this ranking, but dysfunctions of this area are associated with most common RRI located in the knee area [25,26]. Moreover, the hip joint seems to be the most stressed during non-level running [27–29]. To the best of our knowledge, there are no studies on the assessment of implications in mountain running training regarding the ROM and strength of the hip and ankle, as well as postural control in highly trained athletes. These data may be valuable for physiotherapists as well as strength and conditioning coaches involved in developing exercise programmes focused on compensating the negative consequences of mountain running training and/or directed at reducing the risk of RRI in athletes practicing this type of activity. Moreover, if mountain running training turns out to improve postural control, it would be an interesting endurance alternative to strength training on unstable surfaces aimed at balance development in athletes. We hypothesise that mountain running training, in which UR, DR, unstable ground and large training loads are present, may cause de cits in hip and ankle ROM as well as strength, and may improve dynamic postural control. Therefore, the aim of the present cross-sectional study was to compare MR and NR on ROM and strength in the hip and ankle, as

hypothesise that mountain running training, in which UR, DR, unstable ground and large training loads are present, may cause de cits in hip and ankle ROM as well as strength, and may improve dynamic postural control. Therefore, the aim of the present cross-sectional study was to compare MR and NR on ROM and strength in the hip and ankle, as well as dynamic postural control.

J. Clin. Med.2023,12, 2715 3 of 10 2. Materials and Methods 2.1. Participants The study involved 30 highly trained MRs and 32 recreationally active NRs. Basic characteristic of studied populations are showed in Table. The inclusion and exclusion criteria are presented in Table. The participants were informed about the research protocol and provided their written informed consent to participate in the study. All procedures were carried out in accordance with the 1964 Declaration of Helsinki and its subsequent amendments. Consent to perform testing was provided by the Bioethics Committee at the Regional Medical Chamber in Krakow (no. 206/KBL/OIL/2022). Table 1.Basic characteristics (mean (SD)) of the studied populations. Mountain Runners Non- Runners p Test Power Age (years) 28.5 (6.6) 21.8 (2.5) 0.000 * ,M-W 0.99 Body height (cm) 179.1 (7.4) 177.2 (7.0) 0.315 T 0.18 Body mass (kg) 71.5 (7.4) 79.6 (11.0) 0.001 * ,CC 0.92 Body mass index (kg m 2 ) 22.7 (1.6) 24.8 (2.9) 0.001 * ,CC 0.94 Training experience (years) 8.4 (3.3) NA NA NA p—probability of type I error, *—statistically signi cant difference, M-W —Mann–Whitney U test, T —t-test, CC —Cochran–Cox test, SD—standard deviation, NA—not applicable. Table 2.Inclusion and exclusion criteria for the study. Mountain Runners Non-Runners Inclusion criteria Age: 18–40 years Sex: male Tier: Highly trained/national-level # Minimum 3 years of training experience Tier: Recreationally active # Exclusion criteria Lower-limb massive injuries in the past (anterior cruciate ligament rupture, hip fractures, instability and recurrent ankle sprains) Minor lower limb injury in past 3 months before examination that may disable performance on the Lower Quarter Y-balance test Diagnosed dif culties in maintaining balance Diagnosed ankle, knee or hip instability # Tier classi cation was performed according to McKay et al. [30]. 2.2. Study Design In this cross-sectional study carried out among highly trained mountain runners (MR) and recreational active non-runners (NR), the following variables were bilaterally assessed: ankle dorsi exion (DF) ROM, internal (IR) and external (ERR) hip rotation ROM and hip abductor (ABD), extensor (EXT) and external rotator (ERS) strength, as well as dynamic postural control. A participant's stance leg was determined as the opposite

cross-sectional study carried out among highly trained mountain runners (MR) and recreational active non-runners (NR), the following variables were bilaterally assessed: ankle dorsi exion (DF) ROM, internal (IR) and external (ERR) hip rotation ROM and hip abductor (ABD), extensor (EXT) and external rotator (ERS) strength, as well as dynamic postural control. A participant's stance leg was determined as the opposite of their self-preferred leg for kicking a ball [31]. Moreover, at baseline, anthropometric measurements were taken. Each measurement was carried out without blinding by one researcher (physiotherapist with 4 years' experience), without a warm-up, between8:00 a.m. and 12:00 a.m. Every participant was instructed not to consume stimulants (e.g., caffeine)

J. Clin. Med.2023,12, 2715 4 of 10 and/or alcohol on the test day and not to perform heavy endurance or strength exercise 36–48 h prior to testing. 2.3. Range of Motion Measurements ROM assessment was performed using the Baseline digital inclinometer (RMS UK Ltd., London, UK). The mean of 3 measurements was considered for analysis. Ankle DF ROM was measured during the Weight-Bearing Lunge Test, using the protocol described by Bennell et al. [32]. The participant stood facing the wall with his hands on it. Each subject was instructed to maximally move the knee forward without lifting the heel off the ground. The inclinometer was placed 15 cm below tibial tuberosity to de ne maximal shank inclination. Passive hip IR and ERRROM were measured following the protocol proposed by Carvalhais et al. [33]. The participant was in a prone position on the treatment table with the knee exed to 90 . The participant's pelvis was additionally stabilised by binding to the table using a rigid strap to minimise lumbopelvic compensatory movements during hip rotations. The examiner performed passive hip rotation until he noted tension of the muscles or passive structures of the hip joint stopped this movement. The inclinometer was placed on the lateral shank side for external hip rotation and on the medial shank side for the internal hip. 2.4. Strength Measurements Isometric strength assessment was performed using the MicroFET2 hand-held dy- namometer (Hoggan Health Industries Inc., West Jordan, UT, USA). The participant's pelvis was stabilised by binding to the table using a rigid strap to minimise lumbopelvic com- pensatory movements during the trials. The participants performed 3 maximal isometric contractions for 5 s each with a 15 s rest between trials. The mean of 3 measurements was considered for analysis. The average force value was multiplied by the force arm length and normalised to the body mass (Nm kg 1 ). Arm of force measurements were performed using measuring tape (TK Gruppe Klingler, Hong Kong, China). Body mass was determined using the MC 780 MA analyser (Tanita, Japan). ERShip strength was evaluated in the prone position with 90

for analysis. The average force value was multiplied by the force arm length and normalised to the body mass (Nm kg 1 ). Arm of force measurements were performed using measuring tape (TK Gruppe Klingler, Hong Kong, China). Body mass was determined using the MC 780 MA analyser (Tanita, Japan). ERShip strength was evaluated in the prone position with 90 knee exion using the protocol described by Men- donça [34]. The dynamometer was placed proximally to the medial malleolus. Force arm length represents the linear distance from dynamometer placement to hip axis of rotation. EXT hip strength was measured in the prone position with the knee exed to 90 according to Thorborg et al. [35]. The dynamometer was placed 5 cm proximal to the knee joint line on the posterior thigh. Force arm length represents the linear distance from dynamometer placement to the greater trochanter. ABD hip strength was measured using the protocol described by Bittencourt et al. [36] in the side-lying position. The dynamometer was placed proximally to the lateral femoral condyle. Force arm length represents the linear distance from dynamometer placement to the greater trochanter. 2.5. Dynamic Postural Control Assessment Dynamic postural control was assessed using the YBT-LQ. Each participant performed 6 training and 3 testing trials in each direction (ANT, PL, PM) for both stance (SL) and kicking leg (KL) using the Y-balance test kit (Move2Perform, Evansville, IN, USA) [37]. Training and testing trials were separated by a 1 min rest. Prior to performing the trials, all participants received verbal instruction and visual demonstration. Each participant performed the single-leg stance barefoot on a starting block. They used the opposite leg as the reaching one to push the reach indicator box as far as possible in the following directions and order: anterior (ANT), posteromedial (PM) and posterolateral (PL). Attempts did not count if the participant was unable to maintain single-leg balance throughout movement, kicked the indicator box or did not return to centre position with maintained balance. The mean of 3 testing trials in each direction was used for further analysis. Scores were calculated by dividing the average

directions and order: anterior (ANT), posteromedial (PM) and posterolateral (PL). Attempts did not count if the participant was unable to maintain single-leg balance throughout movement, kicked the indicator box or did not return to centre position with maintained balance. The mean of 3 testing trials in each direction was used for further analysis. Scores were calculated by dividing the average reach distance (in cm) by the participant's leg length, which was measured using measuring tape (TK Gruppe Klingler, China) in the supine

J. Clin. Med.2023,12, 2715 5 of 10 position from the anterior superior iliac spine to the medial malleolus [38]. To calculate the composite score sum of average reaches in each of the 3 directions, the value was divided by 3 leg lengths and multiplied by 100%. Normalised reach distance was calculated as the average reach distance divided by the leg length and multiplied by 100% [39]. 2.6. Statistical Analysis Statistical analysis was carried out using Statistica 13.3 software (TIBCO Software Inc., Palo Alto, CA, USA). The differences between groups in the measured variables were evaluated with the independent samplet-test, the Cochran–Cox test or the Mann– Whitney U test, depending on variable distribution and equality of variance. The variable distribution in groups was examined with the Shapiro–Wilk test. In turn, the equality of variable variance between groups was assessed using Levene's test. The probability of type I error below 0.05 was adopted as the level of signi cance. The test power was calculated post hoc using G*Power 3.1.9.6 software (Franz Faul, Universität Kiel, Kiel, Germany). 3. Results 3.1. Range of Motion MRs had signi cantly smaller hip ERRROM in relation to NRs (Table). Table 3.Results (mean (SD)) of ROM measurement.Mountain Runners Non-Runners p Test Power Ankle dorsi exion ROM ( ) Kicking leg 42.8 (4.8) 42.3 (5.4) 0.692 T 0.07 Stance leg 42.7 (5.3) 42.8 (4.4) 0.920 T 0.05 Kicking/stance leg ratio1.00 (0.11) 0.99 (0.83) 0.658 T 0.05 Hip internal rotation ROM ( ) Kicking leg 25.0 (10.8) 25.6 (9.3) 0.794 T 0.06 Stance leg 36.6 (10.9) 37.5 (11.9) 0.761 T 0.06 Kicking/stance leg ratio0.67 (0.20) 0.68 (0.18) 0.779 T 0.05 Hip external rotation ROM ( ) Kicking leg 57.7 (10.7) 64.8 (9.5) 0.007 * ,CC 0.79 Stance leg 41.6 (10.5) 47.1 (11.9) 0.054 T 0.49 Kicking/stance leg ratio1.43 (0.25) 1.42 (0.24) 0.965 T 0.05 ROM—range of motion, p—probability of Type I error, *—statistically signi cant difference, T —t-test, CC —Cochran–Cox test. 3.2. Strength MRs had signi cantly lower hip ERSand EXT strength in relation to NRs (all differ- ences registered for KL). Moreover, MR characterised the KL/SL ratio for ERSstrength

This study compares mountain runners and non-runners on hip and ankle strength and range of motion.