Differentiating Endurance-and Speed-Adapted Types of Elite and World Class Milers According to Biomechanical, Pacing and Perceptual Responses during a Sprint Interval Session

s to compare pacing, biomechanical and perceptual responses between elite speed-and endurance-adapted milers during a sprint interval training session (SIT). Twenty elite and world-class middle-distance runners (male:n= 16, female: n = 4; 24.95 5.18 years; 60.89 7 kg) were classi ed as either speed- or endurance-adapted milers according to their recent performances at 800 m or longer races than 1500 m (10 subjects per group). Participants performed 10 repetitions of 100 m sprints with 2 min of active recovery between each, and performance, perceptual and biomechanical responses were collected. The difference between accumulated times of the last and the rst ve repetitions was higher in speed-adapted milers (ES = 1.07) displaying a more positive pacing strategy. A higher coef cient of variation (CV%) was

group). Participants performed 10 repetitions of 100 m sprints with 2 min of active recovery between each, and performance, perceptual and biomechanical responses were collected. The difference between accumulated times of the last and the rst ve repetitions was higher in speed-adapted milers (ES = 1.07) displaying a more positive pacing strategy. A higher coef cient of variation (CV%) was displayed across the session by speed-adapted milers in average repetition time, contact time, and affective valence (ES 1.15). Speed-adapted milers experienced lower rates of valence after the 4th repetition excepting at the 8th repetition (ES 0.99). Speed-adapted milers may need to display a more positive pacing pro le than endurance-adapted milers and, therefore, would experience lower levels of affective valence and a more rapid increase of ground contact time during a SIT. Keywords:athletics; exercise performance; perceptions; coaching 1. Introduction The 800 m, 1500 m, and 3000 m events are considered middle-distance running races and at the elite level are typically completed in between 1.6 and 10 min [1], meaning a range of physiological and biomechanical qualities, which determines performance in these events. Although middle-distance running events are characterized by a high relative contribution from the aerobic energy system [2] and performance in these events is highly correlated with the speed at which maximal oxygen uptake is achieved (vVO2max) [3], the high speeds at which elite races are completed demand high levels of biomechani- cal power output and a well-developed anaerobic capacity [4]. However, 1500 m and mile runners (milers) can approach the event from either the 800 m or 3000 m ends of the speed-endurance spectrum due to differing physiological adaptations achieved through speci c-distance training or innate characteristics such as the individual's muscle ber [5]. Consequently, they may display different performance-related characteristics (i.e., a800–1500 mrunner would be able to produce greater power biomechanical output [6] whereas a 1500–3000 m runner would display a higher relative contribution of the aerobic energy system [2]. We can, therefore, classify these runners as either endurance-adapted Int. J. Environ. Res. Public Health2021,18, 2448.

different performance-related characteristics (i.e., a800–1500 mrunner would be able to produce greater power biomechanical output [6] whereas a 1500–3000 m runner would display a higher relative contribution of the aerobic energy system [2]. We can, therefore, classify these runners as either endurance-adapted Int. J. Environ. Res. Public Health2021,18, 2448.

Int. J. Environ. Res. Public Health2021,18, 2448 2 of 10 or speed-adapted milers. In a similar vein, Nummela and Rusko [7] found a signi cantly greater aerobic contribution for endurance trained subjects compared with sprint trained participants during the rst 30 s of 49 s of exhaustive treadmill running. Conversely, it has been suggested that 800 m runners are required to display high levels of power output early in the race, which are not required for success during the 3000 m event, whereas during the latest stages of the race, the relative contribution of the aerobic energy system increases [6]. Due to differing demands of the events, pacing strategies observed during 800 m world record races are mostly positive (the second half of the race is covered slower than the rst) whereas in longer races such as 5000 m, runners display a fast end spurt [8,9]. From a biomechanical perspective, in middle-distance running races, high ground reaction forces are generated but they are lower than in sprint races [10]. Furthermore, a longer stride and a shorter contact time has been observed in middle-distance runners when compared to long-distance runners [11]. Whilst these biomechanical variables have not been found to discriminate across performance level in runners [12], it has been observed that during a repeated sprint ability (RSA) session, contact time and step length increased with fatigue and lower speed whereas step frequency decreased [13]. Accordingly, speed-adapted milers may be expected to display a more positive pacing pro le when conducting a short interval training (SIT) session than endurance-adapted milers and, although changes in the biomechanical responses are to be expected throughout the session, these might also differ between the two groups. Furthermore, any difference in pacing pro le displayed by the two types of milers may also result in differences in the progression of change of perceptual responses during the SIT session. For example, a greater change in rating of perceived exertion (RPE) across the session in the speed than in endurance-adapted runners might be expected. However, a recently proposed three-dimensional framework of centrally regulated and goal directed exercise behavior

the two types of milers may also result in differences in the progression of change of perceptual responses during the SIT session. For example, a greater change in rating of perceived exertion (RPE) across the session in the speed than in endurance-adapted runners might be expected. However, a recently proposed three-dimensional framework of centrally regulated and goal directed exercise behavior emphasizes the dynamic and complex interplay of sensory, affective, and cognitive processes that underpin perceived fatigability [14]. This framework more comprehensively accounted for perception–thinking– action coupling in response to psychophysiological distress than the traditional Gestalt concept of perceived exertion [14]. Therefore, another psychological variable that has been demonstrated to be implicated in the awareness of achievement of performance is core affect. Speci cally, a more negative affective state or valence is associated with low performance [14,15]. Accordingly, speed-adapted milers may also display a greater change in affective valence than endurance-adapted runners across a SIT session due to their presumably more positive pacing strategy. The analysis of these variables in elite middle-distance runners may help coaches to make correct training decisions regarding the optimal approach that should be used for each type of runner. Therefore, the aim of this study was to compare the different performance, biomechanical and perceptual responses among elite speed- and endurance-adapted milers during a SIT session. 2. Materials and Methods 2.1. Participants Twenty elite middle-distance runners (male: n = 16, female: n = 4; age = 24.95 5.18 years old; body mass = 60.89 7 kg; height = 174.7 6.48 cm) were recruited from a professional middle-distance running group. All participants are currently active at national or international level by the time of writing the present article and 15 of them have been selected by their national federation to compete at international events. Two of the participants competed at two nal races of the 2019 World Championships of Athletics. Runners competed at the 1500 m event regularly. Mean of their 1500 m best performance during the year preceding the study was 230.56 10.88 s for males, and 266.76 6.3 s for females. Participants completed 7.2 1.4 training

federation to compete at international events. Two of the participants competed at two nal races of the 2019 World Championships of Athletics. Runners competed at the 1500 m event regularly. Mean of their 1500 m best performance during the year preceding the study was 230.56 10.88 s for males, and 266.76 6.3 s for females. Participants completed 7.2 1.4 training sessions per week. They had been systematically training for 7.7 3.2 years. Neither physical limitations nor musculoskeletal injuries that could affect testing for at least six months prior to the test were reported. All participants provided written informed consent prior to participation in

Int. J. Environ. Res. Public Health2021,18, 2448 3 of 10 the experimental procedures. The study protocol adhered to the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board of Pablo de Olavide University (935/CEIH/2019). 2.2. Experimental Design An independent measures experimental design was employed involving assessment of performance, biomechanical and psychological variables during one session of high- intensity repetition running. Participants were divided in two groups of ten athletes according to their coach's perceptions. The coach based this decision on the target event for the season, and the type of training being conducting (i.e., lower volume and higher intensity in the training of the milers who also were training for 800 m and higher volume and lower intensity in the training of the milers who also were training for either the 3000 m, 3000 m steeplechase, or 5000 m). Furthermore, this decision was further checked through an analysis of the difference in recent competitive performances in both shorter (i.e., 800 m) and longer (i.e., 3000 m, 3000 m steeplechase, and 5000 m) events than 1500 m. Fastest performance times achieved by participants during competition in the 12 months prior to testing were collected from the World Athletics open access website (www.worldathletics. org Athletics Federations (IAAF) scores [16]. Participants were allocated to groups (speed- or endurance-adapted) depending on whether they achieved a “better” recent performance in either the shorter or longer events than 1500 m event. Participants were requested to arrive for testing in a rested state, thereby having avoided intense exercise during the previous 48 h. They also were instructed to be in a fully hydrated state and having fasted for at least 3 h. These conditions were con rmed by athletes prior to the test. They were asked to prepare their training and diet for 48 h prior to the session, thereby simulating their typical routine before a high-intensity running session or competition. This session was completed at 11 a. m. on a synthetic indoor athletics running track. Temperature and humidity were constantly between 20 C and 22 C and between 35 and 40%.

test. They were asked to prepare their training and diet for 48 h prior to the session, thereby simulating their typical routine before a high-intensity running session or competition. This session was completed at 11 a. m. on a synthetic indoor athletics running track. Temperature and humidity were constantly between 20 C and 22 C and between 35 and 40%. A standardized warm-up protocol was used by all participants, consisting of 15 min of running at a self-selected easy pace, 5 min of joint mobilization exercises, and two 30 m running accelerations. Subsequently, athletes performed 10 bouts of 100 m sprints at the highest possible speed with an active recovery period of 2 min between attempts in which they walked back to the starting point. Performance, biomechanical and perceptual responses were collected from participants across the session. Coef cient of variation for every measure collected from athletes during each repetition (CV%) was calculated using the mean and standard deviation (SD) in order to assess the variability in each variable across the SIT session. Speci c distance length, number of repetitions, and recovery times between repetitions were set in order to induce a demand for high biomechanical outputs without a very high anaerobic glycolytic energy contribution, which also may allow for a suf cient contribution of the aerobic system by means of a high muscle O2demand and greater reliance on oxidative metabolism [17,18]. 2.3. Measures 2.3.1. 100 m Sprint Time and Maximal Speed Sprint times were recorded for both 100 m and 30–40 m distances using photocell timing gates (Polifemo Radio Light Racetime, Microgate, Bolzano, Italy). This intermediate distance was chosen because it has been reported that top speed during a maximal sprint is reached at this point [19]. Participants used a standing start, placing the leadoff foot 1 m behind the rst timing gate. A standard crouched start position was adopted by participants. They placed the toes of their preferred leg just behind the start line. Once in position participants were asked to start the sprint when they would be ready for it. Athletes were instructed to accelerate maximally, thereby

a standing start, placing the leadoff foot 1 m behind the rst timing gate. A standard crouched start position was adopted by participants. They placed the toes of their preferred leg just behind the start line. Once in position participants were asked to start the sprint when they would be ready for it. Athletes were instructed to accelerate maximally, thereby attempting to complete the sprint distance as fast as possible. Athletes wore spike shoes during the SIT.

Int. J. Environ. Res. Public Health2021,18, 2448 4 of 10 2.3.2. Biomechanical Variables Ten meters of optoelectronic system (Optojump Next Microgate, Bolzano, Italy) were installed on the lane of the indoor track from 30 to 40 m to analyze running stride patterns during the maximum velocity phase. Ground contact time, ight time, step frequency, and stride length were measured during this section, which represented the maximal speed phase [19]. 2.3.3. Ratings of Perceived Exertion (RPE) The 15-point (6–20) Borg scale [20] was used to record RPE. Participants were encour- aged to use decimals, and the scale was “anchored” in a way that a previous memory of maximum exhaustion should equate to a score of 20. They were directly requested to report “how hard, heavy, and strenuous this repetition was” [21]. In this way, they were instructed to report the mental sense of effort generated by the task after each repetition. 2.3.4. Core Affect Dynamic changes in core affective state in participants were analyzed through the use of three different psychometric variables [14]. In this way, they were requested to indicate dynamic changes in valence from 5 (“very bad”) to 0 (“neutral”) to +5 (“very good”) after each 100 m repetition using the 11-point Feeling Scale (FS [22]). Participants also had to indicate felt arousal just before the rst 100 m repetition and after each 100 m repetition through the 6-point Felt Arousal Scale (FAS [23]) from 1 (“low activation”) to 6 (“high activation”). Using decimals was recommended in order to rate felt arousal. 2.4. Statistical Analyses Statistical analyses were performed using the Statistical Package for the Social Sciences 24.0 (IBM, Armonk, NY, USA). Data were checked for normality of distribution, equality of variances, and assumption of sphericity as appropriate. Greenhouse–Geisser correc- tions were used if the sphericity assumption was violated. Two-way (group repetitions) repeated measures analysis of variance (ANOVA) was conducted on performance, biome- chanical and perceptual variables with repeated contrast tests and Bonferroni's post hoc tests conducted to identify changes between successive repetitions and between groups for each repetition, respectively. Means and CV% of performance, biomechanical and perceptual variables,

correc- tions were used if the sphericity assumption was violated. Two-way (group repetitions) repeated measures analysis of variance (ANOVA) was conducted on performance, biome- chanical and perceptual variables with repeated contrast tests and Bonferroni's post hoc tests conducted to identify changes between successive repetitions and between groups for each repetition, respectively. Means and CV% of performance, biomechanical and perceptual variables, recent performance in 1500 m, and recent performance achieved at respective events of each group were compared between groups using independent t-tests, Cohen'sd[24] effect sizes (ES), and 95% con dence intervals (95% CI). The same comparisons were conducted with performance, biomechanical and perceptual variables for each repetition between groups and between successive segments for each group where appropriate. Statistical signi cance was accepted atp< 0.05. Cohen'sdwas considered to be either trivial (d< 0.20), small (0.21–0.60), moderate (0.61–1.20), large (1.21–2.00), or very large (2.01–4.00) [25]. Effect sizes of the ANOVA were calculated using eta partial squared (hp 2). In both gures, differences between successive repetitions and between groups at each repetition have been indicated only when the effect size was moderate or larger (d 0.61) and the 95% CI did not cross zero. 3. Results In Table, means and SD of performance, pacing, biomechanical and perceptual variables collected from both speed- and endurance-adapted milers and ES and 95% CI from comparison of these variables between groups are displayed. Both groups displayed similar recent performances in the 1500 m event (Table) and the only signi cant difference between groups was found between accumulated times achieved in the rst ve and last ve 100 m repetitions. Therefore, although both groups displayed a positive pacing pro le, it was more pronounced in the speed- than endurance-adapted milers (Table). However, despite displaying no signi cant differences, the rest of the variables showed either small or moderate ES. Speed-adapted milers performed faster repetitions and displayed a faster

Int. J. Environ. Res. Public Health2021,18, 2448 5 of 10 maximal speed, a lower ight time, contact time, and valence, and a higher step frequency, stride length RPE, and felt arousal than endurance-adapted milers (Table). Table 1. Means and standard deviations (SD) of performance, biomechanical and perceptual variables collected to speed- and endurance-adapted milers. Effect sizes (ES),p-value and con dence intervals (95% CI) calculated from the comparison of these variables between groups. Performance, Biomechanical and Perceptual Variables Mean SD ES p 95% CI Speed-Adapted Endurance- Adapted Performance (IAAF) 977.8 132.65 980.9 110.68 0.03 0.86 118.14–111.94 Other perform (IAAF) 944.4 164.98 1003.5 127.6 0.4 0.38 197.67–79.47 Times of 100 m rep (s) 12.97 1.03 13.26 0.72 0.33 0.47 1.12–0.54 Maximal speed (m/s) 8.53 0.62 8.28 0.45 0.45 0.32 0.27–0.76 Flight time (s) 0.126 0.006 0.129 0.01 0.31 0.49 0.01–0.005 Contact time (s) 0.12 0.007 0.13 0.008 0.21 0.64 0.09–0.005 Frequency (steps/s) 4.02 0.13 3.95 0.14 0.45 0.32 0.07–0.19 Stride length (m) 212.28 11.54 209.75 11.79 0.22 0.63 8.43–13.48 RPE 16.14 1.86 15.48 1.85 0.36 0.44 1.08–2.4 Valence 1.12 1.7 0.29 1.96 0.77 0.09 3.13–0.31 Felt arousal 3.64 0.87 3.37 0.98 0.29 0.53 0.61–1.13 Halves difference (s) 2.36 0.93 1.03 1.48 1.07 0.03 0.17–2.49 Performance (IAAF): International Association of Athletics Federations (IAAF) performance scores at 1500 m event; other perform: IAAF performance scores of each group at either shorter or longer events than 1500 m event, respectively. rep: repetition; frequency: step frequency; RPE: rate of perceived exertion; halves difference: difference between accumulated times registered from the rst 5 and last 5 100 m repetitions; SD: standard deviations; ES: Cohen'sdeffect size;p:p-value; CI: con dence intervals. In Table, means and SD of CV% of performance, biomechanical and perceptual variables are displayed and comparisons between groups of these variables are shown. No signi cant differences were found between groups in either 1500 m performance or longer and shorter distances. A higher CV% in the speed- than in endurance-adapted milers with moderate ES was shown in the average of repetition times and with large ES in contact time and valence (Table). Table 2. Means and standard

This study compares responses of elite milers during sprint interval training.