Influence of Running Surface Using Advanced Footwear Technology Spikes on Middle- and Long-Distance Running Performance Measures

e:This study evaluated the effects of advanced footwear technology (AFT) spikes on running performance measures, spatiotemporal variables, and perceptive parameters on different surfaces (track and grass).Methods:Twenty-seven male trained runners were recruited for this study. In Experiment 1, participants performed 12×200 m at a self-perceived 3000 m running pace with a recovery of 5 min. Performance (time in each repetition), spatiotemporal, and perceptive parameters were measured. In Experiment 2, participants performed 8×5 min at 4.44 m/s while energy cost of running (W/kg), spatiotemporal, and perceptive parameters were measured. In both experiments the surface was randomized and mirror order between spike conditions (Polyether Block Amide (PEBA) and PEBA + Plate) was used.Results:Experiment 1: Runners were faster on the track (p= 0.002) and using PEBA + Plate spike (p= 0.049). Experiment 2: Running on grass increased energy cost (p= 0.03) and heart rate (p< 0.001) regardless of the spike used, while PEBA + Plate spike reduced respiratory exchange ratio (RER) (p= 0.041). Step frequency was different across surfaces (p< 0.001) and spikes (p= 0.002), with increased performance and comfort perceived with PEBA + Plate spikes (p< 0.001;p= 0.049).Conclusions:Running on the

Experiment 2: Running on grass increased energy cost (p= 0.03) and heart rate (p< 0.001) regardless of the spike used, while PEBA + Plate spike reduced respiratory exchange ratio (RER) (p= 0.041). Step frequency was different across surfaces (p< 0.001) and spikes (p= 0.002), with increased performance and comfort perceived with PEBA + Plate spikes (p< 0.001;p= 0.049).Conclusions:Running on the track surface with PEBA + Plate spikes enhanced auto-perceived 3000 m running performance, showed lower RER, and improved auto-perceptive comfort and performance. Running on grass surfaces increased energy cost and heart rate without differences between spike conditions. Keywords:super spike; carbon fiber plate; athletics; cross-country running 1. Introduction During running, elastic storage and return of mechanical energy in tendons minimize the metabolic cost of running [1]. However, optimizing external storage and return of energy at the foot–ground interface during ground contact can provide additional metabolic savings [2,3]. Hoogkamer et al. [4] showed that the first advanced footwear technology (AFT) with Polyether Block Amide (PEBA) returned more than twice mechanical energy when compressed with forces similar to vertical ground reaction while running and lowered metabolic cost by 4%, compared to other traditional Ethyl Vinil Acetate (EVA) running shoes. The AFT spikes [spikes that combine lightweight, compliant, resilient foams, i.e., PEBA and a stiff curved (nylon/PEBA/carbon fiber) plate] have recently been shown to improve running economy (RE), expressed as lower energy cost (4–5%) and middle distance performance around 2% running [5,6] similar to their corresponding AFT road shoes [4]. In track races, the performance improvements have been similar, improving more in events where speed is higher [7]. Sports2024,12, 329.

Sports2024,12, 329 2 of 11 Rodrigo-Carranza et al. [6] showed that the AFT spikes that combined PEBA with a stiff curved carbon fiber plate were the best option to improve the 800 m (∼6.5 m/s) performance. Runners ran faster in PEBA (1.2%) and PEBA + Plate (2.8%) compared to EVA spike. However, PEBA + Plate was better than PEBA condition (1.5%). Nevertheless, RE at 5 m/s was better in PEBA (5.1%) and PEBA + Plate (4.0%) than EVA spike. This suggests that the speed of the track event may influence the design of the best spike for each distance. Moreover, the improvements in both AFT spikes were accompanied by small spatiotemporal modifications, especially in an increase in stride length [5,6]. Historically, spikes have been used in athletics for track events and also for cross- country events that are characterized by courses of 1500 m (short cross or team relay) to 10,000 m in nature with generally soft surfaces such as grass, sand, or woodland courses. These events might also include stretches of gravel paths and hills. In contrast to running on tracks, cross-country surfaces are softer and more deformable. It has been shown that more compliance surfaces with a greater amount of cushioning could improve RE [2,3] with 2.5% slower stride frequency, ~5 cm longer stride length, and 5.9% longer contact time running shod compared to unshod on a rigid treadmill. However, no differences were found running unshod on the treadmill with different amounts of cushioning (10 vs. 20 mmof EVA), which indicates that the cushioning of the surface influences the cushioning of the shoe. Nevertheless, on extremely deformable surfaces, energy cost could increase due to increasing center-of-mass oscillation (vertical oscillation), contact time, and the corresponding decrease in leg stiffness, all of which have been related to a deterioration of RE [8]. This suggests that new AFT with more compliant materials may not improve or even worsen RE/running performance on these types of surfaces. This raises the question of whether different AFT spikes influence RE and running performance differently depending on the type of surface (track/grass) and the inten- sity/distance

all of which have been related to a deterioration of RE [8]. This suggests that new AFT with more compliant materials may not improve or even worsen RE/running performance on these types of surfaces. This raises the question of whether different AFT spikes influence RE and running performance differently depending on the type of surface (track/grass) and the inten- sity/distance tested. Therefore, the aim of the current study was to examine the influence of different AFT spike components on middle- and long-distance performance measures and spatiotemporal variables on different athletic surfaces. We hypothesized that at middle- distance pace, AFT combined with a modern foam with a curved carbon fiber plate would have the largest improvement in running speed, while PEBA-only would have better RE performance. However, the performance using AFT spikes would be similar between PEBA and PEBA + Plate spikes when running on grass. Small spatiotemporal modifications, such as a reduction in stride frequency, are expected when using PEBA + Plate compared to traditional PEBA spikes with lower differences while running on grass. 2. Materials and Methods 2.1. Participants Twenty-seven (Experiment 1: n = 15; Experiment 2: n = 12) trained runners (age: 24.84±5.20 years ; body mass: 63.32±6.27 kg; height: 175.73±6.79 cm; performance: World Athletics (WA) score in distance between 5 km and 21 km (score scale used to com- pare performance across different distances): 779.84±117.05 points) were recruited for this study. The recruitment process was carried out by asking local running clubs. The partici- pants were different in each intervention but with very similar characteristics (Experiment 1: age: 24.11±5.83 years; body mass: 64.00±7.28 kg; height:175.83±7.24 cm ; perfor- mance: WA score: 717.00±86.23 points; Experiment 2: age: 25.91±3.92 years; body mass: 62.18±4.30 kg; height: 174.91±6.57 cm; performance: WA score: 861.72±96.69 points). The inclusion criteria were the following: (1) ranged between 18 and 35 years old; (2) participation in endurance training for at least 5 days per week; (3) <35 min in 10 k event, (4) fitting a men’s 42–44 EU shoe size; and (5) to be a spikes and advanced footwear technology user. The exclusion criteria were the

score: 861.72±96.69 points). The inclusion criteria were the following: (1) ranged between 18 and 35 years old; (2) participation in endurance training for at least 5 days per week; (3) <35 min in 10 k event, (4) fitting a men’s 42–44 EU shoe size; and (5) to be a spikes and advanced footwear technology user. The exclusion criteria were the following: (1) not being familiar with AFT spikes, and (2) being injury-free during the previous 6 months. Participants were categorized as nationally trained runners, as they compete at the national level in cross- country, track, and road racing championships [9].

Sports2024,12, 329 3 of 11 Before this study, all participants were informed about the testing protocols and the possible risks involved; moreover, they were requested to provide written informed consent. This study was performed using the principles of the Declaration of Helsinki (December 2013, Brazil), and the experimental protocols were approved by the Ethics Committee of the local university (CEIC924). 2.2. Spike Characteristics Two experimental AFT spikes were tested: (1) spikes that combine a curved carbon fiber plate with PEBA midsole foam, and (2) spikes with PEBA midsole foam without ele- ments that increase the longitudinal bending stiffness as a control (Figure). All spikes used 6 mm spike pins for traction. The weight of the spikes was 163 g for thePEBA + Platecon- dition and 142 g for the PEBA condition, both in EU42 (Table). Participants could see the spikes they wore but could not manipulate them or learn more about their characteristics.Sports 2024, 12, x FOR PEER REVIEW 3 of 12 categorized as nationally trained runners, as they compete at the national level in cross- country, track, and road racing championships [9]. Before this study, all participants were informed about the testing protocols and the possible risks involved; moreover, they were requested to provide written informed con- sent. This study was performed using the principles of the Declaration of Helsinki (De- cember 2013, Brazil), and the experimental protocols were approved by the Ethics Com- mittee of the local university (CEIC924). 2.2. Spike Characteristics Two experimental AFT spikes were tested: (1) spikes that combine a curved carbon fiber plate with PEBA midsole foam, and (2) spikes with PEBA midsole foam without elements that increase the longitudinal bending stiffness as a control (Figure 1). All spikes used 6 mm spike pins for traction. The weight of the spikes was 163 g for the PEBA + Plate condition and 142 g for the PEBA condition, both in EU42 (Table 1). Participants could see the spikes they wore but could not manipulate them or learn more about their character- istics. Figure 1. Force–displacement representation for AFT spikes condition used in this study. (A)

for traction. The weight of the spikes was 163 g for the PEBA + Plate condition and 142 g for the PEBA condition, both in EU42 (Table 1). Participants could see the spikes they wore but could not manipulate them or learn more about their character- istics. Figure 1. Force–displacement representation for AFT spikes condition used in this study. (A) AFT spike with PEBA midsole foam + carbon plate (Cloudspike Citus). (B) AFT spike PEBA midsole foam (Clouspike XC). Table 1. Characteristics of experimental spikes for EU42. Characteristics PEBA + Plate PEBA Carbon plate Full length No Midsole foam PEBA PEBA Mass (g) 163 142 Stiffness (N/mm) 155.6 152.1 Energy loss (kN/mm) 1.0 1.1 Energy return (J) 5.7 3.7 Resistance (%) 83.7 82.3 Midsole thickness (mm) 24.5 19.5 The force–displacement relationship of the spikes was determined by a compression test on the complete spike (including the shoe upper), where a custom-made structure simulating a size EU42 foot was attached to a material testing machine that measures force Figure 1.Force–displacement representation for AFT spikes condition used in this study. (A) AFT spike with PEBA midsole foam + carbon plate (Cloudspike Citus). (B) AFT spike PEBA midsole foam (Clouspike XC). Table 1.Characteristics of experimental spikes for EU42. Characteristics PEBA + Plate PEBA Carbon plate Full length No Midsole foam PEBA PEBA Mass (g) 163 142 Stiffness (N/mm) 155.6 152.1 Energy loss (kN/mm) 1.0 1.1 Energy return (J) 5.7 3.7 Resistance (%) 83.7 82.3 Midsole thickness (mm) 24.5 19.5 The force–displacement relationship of the spikes was determined by a compression test on the complete spike (including the shoe upper), where a custom-made structure simulating a size EU42 foot was attached to a material testing machine that measures force and displacement (Zwick/Roell, Ulm-Einsingen, Germany). A force of 1800 N was applied at 2 Hz in the forefoot during 60 cycles, and the average of the last 10 cycles was used for characterizing of spikes. Longitudinal bending stiffness was calculated as the line between 0 and 1500 N. 2.3. Experimental Design Using a counter-balanced randomized experimental design, we evaluated the effects of wearing two AFT

A force of 1800 N was applied at 2 Hz in the forefoot during 60 cycles, and the average of the last 10 cycles was used for characterizing of spikes. Longitudinal bending stiffness was calculated as the line between 0 and 1500 N. 2.3. Experimental Design Using a counter-balanced randomized experimental design, we evaluated the effects of wearing two AFT spikes, which differ mainly in the midsole design through the insertion

Sports2024,12, 329 4 of 11 of a carbon fiber plate on different surfaces (track and grass). The experimental design consisted of two experiments carried out in different groups (but with homogeneous char- acteristics) and on different days. All participants were asked to avoid strenuous exercise (no intense exercise in the previous 48 h), caffeine, and alcohol intake 24 h before the visit. The test was carried out on an outdoor athletics track (400 m) with similar environmental conditions in all sessions (529 m altitude, 20–25 ◦ C, and 35–40% relative humidity). 2.4. Procedure 2.4.1. Experiment 1: Efforts at Self-Perceived 3000 m Race Pace Warm-up consisted of 10 min of jogging and two runs of 200 m at a self-perceived 3000 m race pace for familiarization. Then, participants performed 12 repetitions of200 m at auto-perceived intensity [5] (Figure), two repetitions with each spike condition and on each surface, in a mirror order in a randomized order of surface condition (i.e., a1–b1– b1–a1–a2–b2–b2–a2). To minimize any confounding effects of participants running the first (excitement) or last (“emptying the tank”) trials at a higher effort, the number of trials that we told the participants to run was greater (12 repeats) than the number of trials they would actually run [5], thus the remaining two repetitions were performed in case of failure of a previous measurement. If the whole procedure was correct, participants performed 10 repetitions. Participants were not informed of the time achieved in each repetition. Rest between repetitions was 5 min. Before each repetition, participants put on the spikes and performed a progressive run of ~100 m toward the starting line to test each spike. Then, they walked the final 100 m to the start line to avoid fatigue.Sports 2024, 12, x FOR PEER REVIEW 4 of 12 and displacement (Zwick/Roell, Ulm-Einsingen, Germany). A force of 1800 N was applied at 2 Hz in the forefoot during 60 cycles, and the average of the last 10 cycles was used for characterizing of spikes. Longitudinal bending stiffness was calculated as the line between 0 and 1500 N. 2.3. Experimental Design Using a counter-balanced

FOR PEER REVIEW 4 of 12 and displacement (Zwick/Roell, Ulm-Einsingen, Germany). A force of 1800 N was applied at 2 Hz in the forefoot during 60 cycles, and the average of the last 10 cycles was used for characterizing of spikes. Longitudinal bending stiffness was calculated as the line between 0 and 1500 N. 2.3. Experimental Design Using a counter-balanced randomized experimental design, we evaluated the effects of wearing two AFT spikes, which differ mainly in the midsole design through the inser- tion of a carbon fiber plate on different surfaces (track and grass). The experimental design consisted of two experiments carried out in different groups (but with homogeneous char- acteristics) and on different days. All participants were asked to avoid strenuous exercise (no intense exercise in the previous 48 h), caffeine, and alcohol intake 24 h before the visit. The test was carried out on an outdoor athletics track (400 m) with similar environmental conditions in all sessions (529 m altitude, 20–25 °C, and 35–40% relative humidity). 2.4. Procedure 2.4.1. Experiment 1: Efforts at Self-Perceived 3000 m Race Pace Warm-up consisted of 10 min of jogging and two runs of 200 m at a self-perceived 3000 m race pace for familiarization. Then, participants performed 12 repetitions of 200 m at auto-perceived intensity [5] (Figure 2), two repetitions with each spike condition and on each surface, in a mirror order in a randomized order of surface condition (i.e., a1–b1– b1–a1–a2–b2–b2–a2). To minimize any confounding effects of participants running the first (excitement) or last (“emptying the tank”) trials at a higher effort, the number of trials that we told the participants to run was greater (12 repeats) than the number of trials they would actually run [5], thus the remaining two repetitions were performed in case of fail- ure of a previous measurement. If the whole procedure was correct, participants per- formed 10 repetitions. Participants were not informed of the time achieved in each repeti- tion. Rest between repetitions was 5 min. Before each repetition, participants put on the spikes and performed a progressive run of ~100 m toward the starting

repetitions were performed in case of fail- ure of a previous measurement. If the whole procedure was correct, participants per- formed 10 repetitions. Participants were not informed of the time achieved in each repeti- tion. Rest between repetitions was 5 min. Before each repetition, participants put on the spikes and performed a progressive run of ~100 m toward the starting line to test each spike. Then, they walked the final 100 m to the start line to avoid fatigue. Figure 2. Experimental design. (A) Experiment 1: Efforts at self-perceived 3000 m race pace. (B) Experiment 2: Running economy protocol at 4.44 m/s. Figure 2.Experimental design. (A) Experiment 1: Efforts at self-perceived 3000 m race pace. (B) Experiment 2: Running economy protocol at 4.44 m/s. 2.4.2. Experiment 2: Running Economy Protocol at Moderate Intensity After a standardized warm-up of 10 min of jogging, participants completed 8 rep- etitions of 5 min at 4.44 m/s (3:45 min/km) (Figure). We chose the specific intensity so participants should be able to run below the second ventilatory threshold to ensure steady-state VO2measurement to evaluate RE. They performed two trials in each spike and surface condition, following a mirror order with the surface condition randomized (same as Experiment 1). To ensure that participants maintained a constant pace during each repetition, they were given an acoustic signal each 100 m (split times of 22.5 s for the pace of 3:45 min/km). Rest between repetitions was 5 min, allowing them to change spikes. 2.5. Measurements The main spatiotemporal parameters of the gait cycle (contact time [CT] and step frequency [SF]) were measured for each step during both experiments by using an inertial measurement unit (Stryd Power Meter, Stryd Inc., Boulder, CO, USA) with a sampling

Sports2024,12, 329 5 of 11 frequency of 1000 Hz. The Stryd Power Meter device has shown adequate validity and reliability compared to optical measurement devices and slow-motion recording to measure spatiotemporal parameters [10]. This device does not need any calibration; according to the manufacturer team, it is ready to use out of the box [11]. In Experiment 1, each repetition was recorded using Witty photocells (Microgate, Bolzano, Italy) in an intermediate segment of 25 m. In this way, we ensured that the self-perceived speed measured was accurate. To avoid incorporating the acceleration into the average data, the intermediate time for 25 m was measured on the straight during a segment between 125 and 150 m. The spatiotemporal parameters were measured during that segment. During the RE efforts (Experiment 2), respiratory variables were measured, specifi- cally those related to gas exchange, including carbon dioxide production (VCO2), oxygen consumption (VO2), and respiratory exchange ratio (RER), using the Cosmed K5 Wearable Metabolic System (COSMED, Rome, Italy), which was warmed up for a minimum of 30 mincalibrated with high-grade calibration gases provided by the manufacturers and by pumping gas with a 3 L calibration syringe through the flow meters, all following the recommendations of the manufacturers. VO2values, collected during the two last minutes of each 5-min trial, were used to calculate RE in W/kg [12]. We expressed RE such as cost (W/kg). The spatiotemporal parameters were measured during the entire effort. At the end of each repetition with each spike condition in both experiments, par- ticipants provided their perception of spike comfort and performance enhancement on a subjective scale [13] from 0 to 100. The questions were: “How comfortable were the spikes?” and “How much do you think the spikes help you during running?”. The corre- sponding scores for this scale were from 0 = “least comfortable spike I have ever worn” to 100 = “most comfortable spike I have ever worn” and from 0 = “least helpful spike I have ever worn” to 100 = “most helpful spike I have ever worn”, respectively. 2.6. Statistical Analysis Statistical analyses were carried out using IBM

This study examines the impact of footwear technology on running performance across different surfaces.