Abstract
mportant skill in the downhill sections of trail running; however, its actual role in the performance of this sport is unknown. The aim of the study was to evaluate the correlation of reactive agility (RA) and certain biomechanical parameters with the performance of runners when performing trail running descents. Nine amateur trail runners (four women and five men) performed a session of change of direction, RA, and 15 m linear sprint tests. In a second session, they performed a trail running race of 400 m with a negative elevation gain of 40 m. The relationship between the variables obtained in both sessions was evaluated using Pearson’s correlation coefficient. The results revealed significant correlations of performance during the trail running descent, with the time of the 15 m linear sprint (r = 0.77,ρ≤0.05.), 5 m linear sprint (r = 0.79,ρ≤0.05.), and with the reaction time in the reactive agility test with a sport-specific stimulus (r = 0.82,ρ≤0.05.). The correlations found in the tests suggest
evaluated using Pearson’s correlation coefficient. The results revealed significant correlations of performance during the trail running descent, with the time of the 15 m linear sprint (r = 0.77,ρ≤0.05.), 5 m linear sprint (r = 0.79,ρ≤0.05.), and with the reaction time in the reactive agility test with a sport-specific stimulus (r = 0.82,ρ≤0.05.). The correlations found in the tests suggest that reactive agility skills and acceleration abilities have a significant relationship with performance on downhill sections in trail running. Keywords:inertial sensors; spatio-temporal parameters; changes of direction; reaction times; acceleration 1. Introduction According to the International Trail Running Association (ITRA), ‘trail running is a running sport that is practised in the middle of nature, in various types of environments such as forests, deserts, and mountains, crossing different types of terrain such as paths, trails, and even sand or snow’ [1]. This sport involves an added challenge compared to other long-distance running competitions due to the variety of surfaces and inclines of the terrain. Distance is not the only relevant factor, as terrain characteristics and the relationship between distance and elevation trigger the overall level of difficulty of this discipline [1,2]. The key parameters related to performance in long-distance and middle-distance running on flat surfaces have been extensively studied. In the ‘classical’ model, maximal oxygen uptake (VO2max), the percentage of VO2max that can be sustained at a certain sub-maximal speed, lactate threshold, and running economy are the main determinants of performance in races ranging from 5 km to marathons [3,4]. In contrast, the key factors determining runners’ performance on trail terrain are not yet well defined [5], as most studies conducted in recent years have evaluated running on flat surfaces. Therefore, the regulation of locomotor behaviour and motor control in ascents and descents are very interesting elements to increase our knowledge of human locomotion [6]. Appl. Sci.2024,14, 11128.
Appl. Sci.2024,14, 11128 2 of 12 Recently, some studies have been carried out on trail running with the aim of gaining a general understanding of the most important physiological, biomechanical, and neuro- muscular parameters in this sport [6–11], since it has been shown that the classical model is only effective in predicting 48% of performance in short trail running races [11]. It is evident that trail running requires specific physiological and biomechanical capabilities that vary between flat terrain, ascent and descent [9,12–14], and some of the determinants of trail running performance have been described in different investigations [10,11,15,16]. In addition, research has been performed differentiating between uphill and downhill sec- tions [6,7,9,12]. Lemire et al. [9] described the determinants of performance in trail running, differentiating between uphill and downhill sections. They reported that performance in the uphill sections can be predicted at 94% by three determinants, the average speed when reaching VO2max, the body mass index (BMI), and the maximal strength achieved in the knee flexors. In downhill sections, the runner’s performance can be predicted at 84% with the leg stiffness value being taken into account instead of the BMI as one of the determining factors. On the other hand, none of the aforementioned studies have included the runner’s abilities in the downhill sections. In Björklund’s study [5] with a group of runners, it was shown that the greatest variability in performance was generated precisely in the downhill sections. Therefore, it seems reasonable to assume that in addition to the physiological and neuromuscular parameters of the runner, agility factors and psychological factors such as tendency to take risks, fear of falling, and fear of injury may come into play. In this respect, the evidence indicates that the speeds achieved in the downhill sections are much higher than in the uphill sections [5,6,17], requiring shorter contact times and the ability to modify the step frequency [5,9], which places greater demands on the runner’s agility and explosiveness to ensure correct foot placement in each step [9]. Currently, the most accepted definition of agility is that proposed by Sheppard and Young [18], who
the downhill sections are much higher than in the uphill sections [5,6,17], requiring shorter contact times and the ability to modify the step frequency [5,9], which places greater demands on the runner’s agility and explosiveness to ensure correct foot placement in each step [9]. Currently, the most accepted definition of agility is that proposed by Sheppard and Young [18], who defined it as ‘the rapid movement of the whole body, with change of speed or direction in response to a stimulus’. In the literature, the terms ‘Agility’ and ‘Reactive Agility’ (RA) are interchangeably used and are employed in this paper according to the definition of Sheppard and Young [18]. The model of agility proposed by Young et al. [19] outlines potential factors that determine agility. These factors are the ability to process visual information in the sport and competitive environment, the capacity to anticipate events that influence movements, and the ability to recognise sport-specific patterns and knowledge based on previous experience of the game or sport [19]. Therefore, reactive agility comprises many components present in downhill mountain running, such as the correct positioning of the foot, the cognitive components of recognition and anticipation, the speed and technique of the change of direction, and the muscular qualities of the lower limb [18]. Zwierco et al. [20] showed in their study that RA performance is associated with both motor and perceptual-cognitive factors, and Scanlan et al. [21] determined that cognitive factors had a greater influence on RA than physical factors. Therefore, RA tests have also been used to discriminate different levels of athletes in different sports such as rugby and football [22,23]. However, in the current literature, there are no studies that assess the possible relation- ship between the individual’s reactive agility, the performance of runners in trail running descents, and the influence of the biomechanical parameters of the athlete. Understanding this relationship may be of particular interest to coaches and athletes, as this information can be used to improve sporting performance by optimising the training of these variables. Therefore, the main objective of this research was to evaluate the correlation between
the performance of runners in trail running descents, and the influence of the biomechanical parameters of the athlete. Understanding this relationship may be of particular interest to coaches and athletes, as this information can be used to improve sporting performance by optimising the training of these variables. Therefore, the main objective of this research was to evaluate the correlation between reactive agility and performance in downhill sections of amateur trail running runners. Thus, the hypothesis was that the existence of better reactive agility values is related to better performance values in the downhill sections during a trail running test. Likewise, the specific objective was to evaluate the type of RA against numerical stimuli (cognitive stimuli) and sport-specific stimuli, assessing its influence on the possible correlations of
Appl. Sci.2024,14, 11128 3 of 12 the variables extracted during the tests. The hypothesis in relation to this objective is that RA against sport-specific stimuli will have a greater correlation with performance than RA against a cognitive stimulus. 2. Materials and Methods 2.1. Design A cross-sectional observational study was conducted to identify whether reactive agility variables, extracted from change of direction tests, agility tests with numerical stimuli (generic) and sport-specific stimuli, and linear sprint tests correlate with trail running downhill performance and biomechanical parameters of the runners. The study was divided into two sessions, one session of RA testing and one session of timed downhill trail running. The time between each session was a minimum of 48 h to avoid related fatigue and was not longer than two weeks. 2.1.1. First Session In the first session, participants were asked to attend the testing facility in comfortable sports clothing and running shoes. Session one tests consisted of a 15 min warm-up, a 15 m linear sprint test, a 45 ◦ change of direction test (COD 45 ◦ ), a reactive agility test with a generic (numerical) stimulus, and a reactive agility test with a sport-specific stimulus. The procedure for each is later discussed. All participants were orally encouraged throughout the session by the researcher and had rest periods between attempts of each test. 2.1.2. Second Session For session 2, participants were asked to wear comfortable running clothes and trail running shoes. Session two consisted of a 3 km warm-up and time-trial testing with trail- running variable measurements being taken on a downhill trail section. The procedure for this is later discussed. The test section was set at 400 m to minimise the influence of fatigue. Dry trail conditions were standardised by all participants completing testing on a dry day, without rainfall in the preceding days. The downhill course consisted of a rugged terrain characterised by stone-strewn path. The section was not a straight downhill line, meaning some changes of direction were required. The route was marked with white and red ribbons to make it easy to recognise the route. The participants
all participants completing testing on a dry day, without rainfall in the preceding days. The downhill course consisted of a rugged terrain characterised by stone-strewn path. The section was not a straight downhill line, meaning some changes of direction were required. The route was marked with white and red ribbons to make it easy to recognise the route. The participants were instructed to make the descent as fast as possible as if it were a competition and they were orally motivated by the researcher during the test. 2.2. Participants Nine participants (4 women and 5 men), recruited by consecutive sampling among amateur runners from the trail running club ‘Las cabras azules’ (Alcobendas, Spain), partic- ipated in this study. The sample size was determined by the availability of collaborating participants. Of the 11 participants initially recruited, there was one withdrawal during session one due to sustaining an injury and a second participant did not attend session two. This resulted in a final sample size of 9 participants who voluntarily took part in this study, with a mean age of 34±8 years, a height of 171±11 cm, a body mass of 67.5±11.7 kg, a body mass index BMI of 22.95±1.75 kg/m 2 . All participants were of legal age, practised trail running at least once a week, and had at least six months of experience in the sport. Participants were excluded from the study if they had suffered a musculoskeletal injury during the 6 months prior to testing and those who were not currently physically active for any reason. Participants were informed in writing about the risks and benefits of this research before signing their consent to take part in the study. The study was approved by the Research Ethics Committee of the University San Pablo-CEU (662/23/TFM).
Appl. Sci.2024,14, 11128 4 of 12 2.3. Procedures 2.3.1. First Session Linear Sprint 15 m: Participants performed two 15 m sprint tests. The times were recorded by means of four Chronojump ® photoelectric cells (Boscosystem, Barcelona, Spain) placed at 5 m intervals (Start line, 5 m, 10 m and 15 m). Participants were instructed to perform the test as fast as possible. All attempts were followed by 1 min of passive rest. In this test, the variables recorded were the 15 m sprint time and the 5 m sprint time. Both were measured in seconds with an accuracy of milliseconds. The mean of both attempts was recorded for analysis. The time recorded in the first 5 m was subsequently used to personalise the appearance of the visual stimulus in the RA tests and for the discarding of invalid attempts. Change of direction at 45 ◦ (COD): The change of direction test comprised a total distance of 15 m with a change of direction at 45 ◦ at 7.5 m as shown in Figurea. Participants made four attempts, two to the right and two to the left (all in that order). All attempts were followed by 1 min of passive rest. The measures captured were the Total COD Time (measured in seconds); the Initial COD Sprint Time, which comprised the time to perform the 7.5 m sprint from the start photocell; and the Final COD Sprint Time, which was the time to perform the second 7.5 m sprint after the change of direction. The averages of the 4 attempts were recorded for analysis.Appl. Sci. 2024, 14, x FOR PEER REVIEW 4 of 12 Participants were informed in writing about the risks and benefits of this research before signing their consent to take part in the study. The study was approved by the Research Ethics Committee of the University San Pablo-CEU (662/23/TFM). 2.3. Procedures 2.3.1. First Session Linear Sprint 15 m: Participants performed two 15 m sprint tests. The times were recorded by means of four Chronojump ® photoelectric cells (Boscosystem, Barcelona, Spain) placed at 5 m intervals (Start line, 5 m,
take part in the study. The study was approved by the Research Ethics Committee of the University San Pablo-CEU (662/23/TFM). 2.3. Procedures 2.3.1. First Session Linear Sprint 15 m: Participants performed two 15 m sprint tests. The times were recorded by means of four Chronojump ® photoelectric cells (Boscosystem, Barcelona, Spain) placed at 5 m intervals (Start line, 5 m, 10 m and 15 m). Participants were instructed to perform the test as fast as possible. All attempts were followed by 1 min of passive rest. In this test, the variables recorded were the 15 m sprint time and the 5 m sprint time. Both were measured in seconds with an accuracy of milliseconds. The mean of both attempts was recorded for analysis. The time recorded in the first 5 m was subsequently used to personalise the appearance of the visual stimulus in the RA tests and for the discarding of invalid attempts. Change of direction at 45° (COD): The change of direction test comprised a total dis- tance of 15 m with a change of direction at 45° at 7.5 m as shown in Figure 1a. Participants made four attempts, two to the right and two to the left (all in that order). All attempts were followed by 1 min of passive rest. The measures captured were the Total COD Time (measured in seconds); the Initial COD Sprint Time, which comprised the time to perform the 7.5 m sprint from the start photocell; and the Final COD Sprint Time, which was the time to perform the second 7.5 m sprint after the change of direction. The averages of the 4 attempts were recorded for analysis. (a) ( b) ( c) Figure 1. (a) The 45° change of direction test design; (b) design of the reactive agility test in response to a generic stimulus displayed on the screen, RAge. (c) Design of the reactive agility tests with sport-specific stimulus, RAsp. Reactive agility tests with generic stimulus (RAge): Four attempts of the reactive agil- ity test were performed with a generic (numerical) stimulus. The test consisted of the same COD as
design; (b) design of the reactive agility test in response to a generic stimulus displayed on the screen, RAge. (c) Design of the reactive agility tests with sport-specific stimulus, RAsp. Reactive agility tests with generic stimulus (RAge): Four attempts of the reactive agil- ity test were performed with a generic (numerical) stimulus. The test consisted of the same COD as above, but the participant had to make a decision to run to the right or left exit in response to a visual stimulus that was displayed on a screen when passing the 5 m mark (Figure 1b). The time of occurrence of the stimulus was customised according to the mean times recorded over the 5 m of the linear sprint [24]. The stimulus was a random number from 0 to 9; if the number on the screen was an even number, the participant should finish the trial at the right exit, and if the number was odd, the participant should take the left exit. The attempt was discarded if the participant did not make the correct decision or did not reach the 5 m line within the average time recorded in the 5 m sprint test. Everyone was instructed to sprint as fast as possible, make a quick and accurate decision about the stimulus received, and sprint to the finish photocell as fast as possible. All participants were encouraged during the test by the researcher. The measures recorded in this test were RAge Total Time, RAge Reaction Time and RAge Deficit. All variables were recorded by means of photocells. The RAge Total Time Figure 1.(a) The 45 ◦ change of direction test design; (b) design of the reactive agility test in response to a generic stimulus displayed on the screen, RAge. (c) Design of the reactive agility tests with sport-specific stimulus, RAsp. Reactive agility tests with generic stimulus (RAge): Four attempts of the reactive agility test were performed with a generic (numerical) stimulus. The test consisted of the same COD as above, but the participant had to make a decision to run to the right or left exit in response
RAge. (c) Design of the reactive agility tests with sport-specific stimulus, RAsp. Reactive agility tests with generic stimulus (RAge): Four attempts of the reactive agility test were performed with a generic (numerical) stimulus. The test consisted of the same COD as above, but the participant had to make a decision to run to the right or left exit in response to a visual stimulus that was displayed on a screen when passing the 5 m mark (Figureb). The time of occurrence of the stimulus was customised according to the mean times recorded over the 5 m of the linear sprint [24]. The stimulus was a random number from 0 to 9; if the number on the screen was an even number, the participant should finish the trial at the right exit, and if the number was odd, the participant should take the left exit. The attempt was discarded if the participant did not make the correct decision or did not reach the 5 m line within the average time recorded in the 5 m sprint test. Everyone was instructed to sprint as fast as possible, make a quick and accurate decision about the stimulus received, and sprint to the finish photocell as fast as possible. All participants were encouraged during the test by the researcher. The measures recorded in this test were RAge Total Time, RAge Reaction Time and RAge Deficit. All variables were recorded by means of photocells. The RAge Total Time was the time from the start of the test at the start photocell until it cut one of the two finish photocells and completed 15 m. The RAge Reaction Time, defined as the time from the appearance of the visual stimulus on the screen until the first foot-floor contact of the step marking the change of direction [24,25], was calculated a posteriori by analysing the video
Appl. Sci.2024,14, 11128 5 of 12 using Matlab software R2021.b (The MathWorks Inc., Natick, MA, USA). The video was recorded using the video camera of an iPad and an iPhone (Apple Inc., Cupertino, CA, USA) with a sampling rate of 240 Hz, which detected the time at which the stimulus appeared and the time at which the participant had the first contact with the ground, marking the change of direction with an accuracy of 4.16 milliseconds. To avoid bias when analysing the video, they were all analysed by the same researcher. The RAge Deficit was defined as the time difference between performing the reactive agility test with numerical stimulus and the 15 m linear sprint. This measure allowed us to know the additional time required to perform a change of direction with decision-making compared to a purely linear task (sprint) over an equivalent distance [26]. Reactive agility tests with sport-specific stimulus (RAsp): Four attempts of this test were performed with the same conditions and configuration as the reactive agility test with generic (numerical) stimulus. The difference in this reactive agility test was that the stimulus received by the participants was sport-specific, consisting of images of terrain or paths where one of them was dangerous and the other safer for running; the subjects had to divert towards the image that showed more safety (Figurec). The measures were recorded in the same way as in the previous test, Total RAsp Time, RAsp Reaction Time, and RAsp Deficit. All variables were recorded by means of photoelectric cells and videos taken at a sampling rate of 240 Hz. 2.3.2. Second Session The participants completed two time trials on a 400 m descent with a negative differ- ence in altitude of 40 m, average gradient of−10%, and maximum gradient of−17.9%. It had a negative elevation gain of 40 m, average gradient of−10%, and maximum gradient of−17.9%. The overall performance of the test was measured by the total time (seconds) it took the runners to complete the test. This was recorded by the researcher using a Garmin ® digital stopwatch (Olathe, KC, USA). Contact time, flight
Description
This study evaluates the correlation of reactive agility and biomechanical parameters with performance in downhill trail running.