Recreational Runners Gain Physiological and Biomechanical Benefits From Super Shoes at Marathon Paces

PURPOSE

Advanced footwear technology is prevalent in distance running, with research focusing on these "super shoes" in competitive athletes, with less understanding of their value for slower runners. The aim of this study was to compare physiological and biomechanical variables between a model of super shoes (Saucony Endorphin Speed 2) and regular running shoes (Saucony Cohesion 13) in recreational athletes.

METHODS

We measured peak oxygen uptake (VO2peak) in 10 runners before testing each subject 4 times in a randomly ordered crossover design (ie, Endorphin shoe or Cohesion shoe, running at 65% or 80% of velocity at VO2peak [vVO2peak]). We recorded video data using a high-speed camera (300 Hz) to calculate vertical and leg stiffnesses.

RESULTS

65% vVO2peak was equivalent to a speed of 9.4 km·h-1 (0.4), whereas 80% vVO2peak was equivalent to 11.5 km·h-1 (0.5). Two-way mixed-design analysis of variance showed that oxygen consumption in the Endorphin shoe was 3.9% lower than in the Cohesion shoe at 65% vVO2peak, with an interaction between shoes and speed (P = .020) meaning an increased difference of 5.0% at 80% vVO2peak. There were small increases in vertical and leg stiffnesses in the Endorphin shoes (P < .001); the Endorphin shoe condition also showed trivial to moderate differences in step length, step rate, contact time, and flight time (P < .001).

CONCLUSIONS

There was a physiological benefit to running in the super shoes even at the slower speed. There were also spatiotemporal and global stiffness improvements indicating that recreational runners benefit from wearing super shoes.

Estimation of Ground Contact Time with Inertial Sensors from the Upper Arm and the Upper Back

Ground contact time (GCT) is one of the most relevant factors when assessing running performance in sports practice. In recent years, inertial measurement units (IMUs) have been widely used to automatically evaluate GCT, since they can be used in field conditions and are friendly and easy to wear devices. In this paper we describe the results of a systematic search, using the Web of Science, to assess what reliable options are available to GCT estimation using inertial sensors. Our analysis reveals that estimation of GCT from the upper body (upper back and upper arm) has rarely been addressed. Proper estimation of GCT from these locations could permit an extension of the analysis of running performance to the public, where users, especially vocational runners, usually wear pockets that are ideal to hold sensing devices fitted with inertial sensors (or even using their own cell phones for that purpose). Therefore, in the second part of the paper, an experimental study is described. Six subjects, both amateur and semi-elite runners, were recruited for the experiments, and ran on a treadmill at different paces to estimate GCT from inertial sensors placed at the foot (for validation purposes), the upper arm, and upper back. Initial and final foot contact events were identified in these signals to estimate the GCT per step, and compared to times estimated from an optical MOCAP (Optitrack), used as the ground truth. We found an average error in GCT estimation of 0.01 s in absolute value using the foot and the upper back IMU, and of 0.05 s using the upper arm IMU. Limits of agreement (LoA, 1.96 times the standard deviation) were [-0.01 s, 0.04 s], [-0.04 s, 0.02 s], and [0.0 s, 0.1 s] using the sensors on the foot, the upper back, and the upper arm, respectively.

THE RELATIONSHIP BETWEEN LOWER LIMB STIFFNESS AND RUNNING ECONOMY IN CHILD SOCCER PLAYERS

ABSTRACT Introduction Lower limb stiffness has been shown to be associated with running economy (RE) in adults, but this relationship in children remains unclear. Objectives The purpose of this study was to investigate the relationship between lower limb stiffness, RE, and repeated-sprint ability in child soccer players. Methods Twenty-eight male child soccer players (mean age 11.8 ± 0.9 years) participated in the study. RE was determined by measuring the steady-state oxygen uptake (ml/min/kg) at submaximal running speeds of 8 and 9 km/h. Vertical and leg stiffness were calculated from the flight and contact time data obtained during two submaximal running tests. Additionally, vertical stiffness was measured during the maximal and submaximal hopping tests. All participants performed the repeated sprint test consisting of 10 × 20-m all-out sprints interspersed with 20-s active recovery. Results During both submaximal running tests, vertical (r= –0.505 to –0.472) and leg stiffness (r= –0.484 to –0.459) were significantly correlated with RE (p< 0.05). Maximal (r= –0.450) and submaximal hopping stiffness (r= –0.404) were significantly correlated with RE at 8 km/h (p< 0.05). Maximal hopping stiffness was significantly correlated with the best sprint time (r= –0.439) and mean sprint time (r= –0.496) (p< 0.05). Vertical (r= –0.592 to –0.433) and leg stiffness (r= –0.612 to –0.429) at 8 and 9 km/h and submaximal hopping stiffness (r= –0.394) were significantly correlated with the fatigue index (p< 0.05). Conclusions Current findings indicate that the lower limb stiffness may be an important determinant of both RE and repeated-sprint ability in child soccer players. Level of Evidence II; Diagnostic Studies - Investigating a Diagnostic Test.

Influence of lower limb dominance on mechanical asymmetries during high-speed treadmill running

We determine whether mechanical asymmetries differ between dominant and non-dominant legs at fast treadmill speed. Stride temporal variables, derived from high-speed camera recordings, allowed to estimate leg and vertical stiffness through the sine-wave method in 31 uninjured males during treadmill running at 6.67 m.s-1. Lower limb dominance was determined by the triple-jump test. The asymmetry was expressed as dominant-non-dominant and indexed by the absolute asymmetry index (ASI). The lowest and highest mean ASI values were detected for contact time (1.69%) and flight time (5.66%), respectively; ASI values for spring-mass characteristics (2.6% ≤ leg and vertical stiffness, peak vertical force, change in vertical leg length and centre of mass vertical displacement ≤ 4.7%) were within this range. Inter-subject variability in ASI varied substantially among the seven analysed variables with larger and smaller range of variability in ASI found for flight time (0-16.56%) and contact time (0-3.47%), respectively. Because the magnitude of group mean ASI appears inconsistent among stride temporal and spring-mass characteristics, different biomechanical variables should not be used interchangeably to assess laterality effects at fast treadmill speed. The widespread ASI range also indicates that using a 'fixed cut-off' threshold is an arbitrary approach.

Acute Effects of Whole-Body Vibration Warm-up on Leg and Vertical Stiffness During Running

ABSTRACT

Paradisis, GP, Pappas, P, Dallas, G, Zacharogiannis, E, Rossi, J, and Lapole, T. Acute effects of whole-body vibration warm-up on leg and vertical stiffness during running. J Strength Cond Res 35(9): 2433-2438, 2021-Although whole-body vibration (WBV) has been suggested as a suitable and efficient alternative to the classic warm-up routines, it is still unknown how this may impact running mechanics. Therefore, the aim of this study was to investigate the effect of a WBV warm-up procedure on lower-limb stiffness and other spatiotemporal variables during running at submaximal speed. Twenty-two males performed 30-second running bouts at 4.44 m·s-1 on a treadmill before and after a WBV and control warm-up protocols. The WBV protocol (vibration frequency: 50 Hz, peak-to-peak displacement: 4 mm) consisted of 10 sets of 30-second dynamic squatting exercises with 30-second rest periods within sets. Leg and vertical stiffness values were calculated using the spring mass model. The results indicated significant increases only after the WBV protocol for leg stiffness (3.4%), maximal ground reaction force (1.9%), and flight time (4.7%). Consequently, the WBV warm-up protocol produced a change in running mechanics, suggesting a shift toward a more aerial pattern. The functional significance of such WBV-induced changes needs further investigation to clearly determine whether it may influence running economy and peak velocity.

Validity and Reliability of an Instrumented Treadmill with an Accelerometry System for Assessment of Spatio-Temporal Parameters and Impact Transmission

Running retraining programs focused on concurrent feedback of acceleration impacts have been demonstrated to be a good strategy to reduce running-related injuries (RRI), as well as to improve running economy and reduce acceleration impacts and injury running incidence. Traditionally, impacts have been registered by mean of accelerometers attached directly to the athletes, which is inaccessible to the entire population, because it requires laboratory conditions. This study investigated the validity and reliability of a new device integrated directly into the treadmill, compared to a traditional acceleration impact system. Thirty healthy athletes with no history of RRI were tested on two separate days over the instrumented treadmill (AccTrea) and simultaneously with an acceleration impact system attached to the participant (AccAthl). AccTrea was demonstrated to be a valid and reliable tool for measuring spatio-temporal parameters like step length (validity intraclass correlation coefficient (ICC) = 0.94; reliability ICC = 0.92), step time (validity ICC = 0.95; reliability ICC = 0.96), and step frequency (validity ICC = 0.95; reliability ICC = 0.96) during running. Peak acceleration impact variables showed a high reliability for the left (reliability ICC = 0.88) and right leg (reliability ICC = 0.85), and peak impact asymmetry showed a modest validity (ICC = 0.55). These results indicated that the AccTrea system is a valid and reliable way to assess spatio-temporal variables, and a reliable tool for measuring acceleration impacts during running.

Reproducibility of the Evolution of Stride Biomechanics During Exhaustive Runs

Running biomechanics and its evolution that occurs over intensive trials are widely studied, but few studies have focused on the reproducibility of stride evolution in these runs. The purpose of this investigation was to assess the reproducibility of changes in eight biomechanical variables during exhaustive runs, using three-dimensional analysis. Ten male athletes (age: 23 ± 4 years; maximal oxygen uptake: 57.5 ± 4.4 ml0₂·min^-1·kg^-1; maximal aerobic speed: 19.3 ± 0.8 km·h^-1) performed a maximal treadmill test. Between 3 to 10 days later, they started a series of three time-to-exhaustion trials at 90% of the individual maximal aerobic speed, seven days apart. During these trials eight biomechanical variables were recorded over a 20-s period every 4 min until exhaustion. The evolution of a variable over a trial was represented as the slope of the linear regression of these variables over time. Reproducibility was assessed with intraclass correlation coefficients and variability was quantified as standard error of measurement. Changes in five variables (swing duration, stride frequency, step length, centre of gravity vertical and lateral amplitude) showed moderate to good reproducibility (0.48 ≤ ICC ≤ 0.72), while changes in stance duration, reactivity and foot orientation showed poor reproducibility (-0.71 ≤ ICC ≤ 0.04). Fatigue-induced changes in stride biomechanics do not follow a reproducible course across the board; however, several variables do show satisfactory stability: swing duration, stride frequency, step length and centre of gravity shift.

Accurate Estimation of Running Temporal Parameters Using Foot-Worn Inertial Sensors

The aim of this study was to assess the performance of different kinematic features measured by foot-worn inertial sensors for detecting running gait temporal events (e.g., initial contact, terminal contact) in order to estimate inner-stride phases duration (e.g., contact time, flight time, swing time, step time). Forty-one healthy adults ran multiple trials on an instrumented treadmill while wearing one inertial measurement unit on the dorsum of each foot. Different algorithms for the detection of initial contact and terminal contact were proposed, evaluated and compared with a reference-threshold on the vertical ground reaction force. The minimum of the pitch angular velocity within the first and second half of a mid-swing to mid-swing cycle were identified as the most precise features for initial and terminal contact detection with an inter-trial median ± IQR precision of 2 ± 1 ms and 4 ± 2 ms respectively. Using these initial and terminal contact features, this study showed that the ground contact time, flight time, step and swing time can be estimated with an inter-trial median ± IQR bias less than 12 ± 10 ms and the a precision less than 4 ± 3 ms. Finally, this study showed that the running speed can significantly affect the biases of the estimations, suggesting that a speed-dependent correction should be applied to improve the system's accuracy.

Acute Effects of Stretching on Leg and Vertical Stiffness During Treadmill Running

Pappas, PT, Paradisis, GP, Exell, TA, Smirniotou, AS, Tsolakis, CK, and Arampatzis, A. Acute effects of stretching on leg and vertical stiffness during treadmill running. J Strength Cond Res 31(12): 3417-3424, 2017-The implementation of static (SS) and dynamic (DS) stretching during warm-up routines produces significant changes in biological and functional properties of the human musculoskeletal system. These properties could affect the leg and vertical stiffness characteristics that are considered important factors for the success of athletic activities. The aim of this study was to investigate the influence of SS and DS on selected kinematic variables, and leg and vertical stiffness during treadmill running. Fourteen men (age: 22.58 ± 1.05 years, height: 1.77 ± 0.05 m, body mass: 72.74 ± 10.04 kg) performed 30-second running bouts at 4.44 m·s, under 3 different stretching conditions (SS, DS, and no stretching). The total duration in each stretching condition was 6 minutes, and each of the 4 muscle groups was stretched for 40 seconds. Leg and vertical stiffness values were calculated using the "sine wave" method, with no significant differences in stiffness found between stretching conditions. After DS, vertical ground reaction force increased by 1.7% (p < 0.05), which resulted in significant (p < 0.05) increases in flight time (5.8%), step length (2.2%), and vertical displacement of the center of mass (4.5%) and a decrease in step rate (2.2%). Practical durations of SS and DS stretching did not influence leg or vertical stiffness during treadmill running. However, DS seems to result in a small increase in lower-limb force production which may influence running mechanics.

Differences in Spatiotemporal Parameters Between Trained Runners and Untrained Participants

Gómez-Molina, J, Ogueta-Alday, A, Stickley, C, Tobalina, JC, Cabrejas-Ugartondo, J, and García-López, J. Differences in spatiotemporal parameters between trained runners and untrained participants. J Strength Cond Res 31(8): 2169-2175, 2017-The aim of this study was to compare the spatiotemporal parameters of trained runners and untrained participants with the same foot strike pattern (rearfoot) during running at controlled speeds. Twenty-one participants were classified in 2 groups according to their training experience: Trained (n = 10, amateur runners with long distance training experience) and Untrained (n = 11, healthy untrained participants). Anthropometric variables were recorded, and the participants performed both a submaximal (between 9 and 15 km·h) and a graded exercise running test (from 6 km·h until exhaustion) on a treadmill. Physiological (V[Combining Dot Above]O2max, heart rate, running economy [RE], peak speed …) and biomechanical variables (contact and flight times, step rate, and length) were simultaneously registered. Trained runners showed higher step rate and shorter step length than the Untrained group at the same running speeds (between 4 and 7%, p ≤ 0.05) and at the same physiological intensities (between 7 and 11%, p ≤ 0.05). However, there were no differences in contact and flight times between groups. Significant differences (p ≤ 0.05) and large effect sizes (Cohen's d) between groups were found for body mass, sum of 6 skinfolds, V[Combining Dot Above]O2max, peak speed, and ventilatory threshold and respiratory compensation threshold speeds. The Trained group also showed a ∼7% better RE (ml·kg·km) than the Untrained group. In conclusion, adopting higher step rate and shorter step length may be an adaptive mechanism of the Trained group to reduce injury risk and possibly improve RE. However, contact and flight times were consistent regardless of training level.

Similarities and differences among half-marathon runners according to their performance level

This study aimed to identify the similarities and differences among half-marathon runners in relation to their performance level. Forty-eight male runners were classified into 4 groups according to their performance level in a half-marathon (min): Group 1 (n = 11, < 70 min), Group 2 (n = 13, < 80 min), Group 3 (n = 13, < 90 min), Group 4 (n = 11, < 105 min). In two separate sessions, training-related, anthropometric, physiological, foot strike pattern and spatio-temporal variables were recorded. Significant differences (p<0.05) between groups (ES = 0.55–3.16) and correlations with performance were obtained (r = 0.34–0.92) in training-related (experience and running distance per week), anthropometric (mass, body mass index and sum of 6 skinfolds), physiological (VO_2max, RCT and running economy), foot strike pattern and spatio-temporal variables (contact time, step rate and length). At standardized submaximal speeds (11, 13 and 15 km·h^-1), no significant differences between groups were observed in step rate and length, neither in contact time when foot strike pattern was taken into account. In conclusion, apart from training-related, anthropometric and physiological variables, foot strike pattern and step length were the only biomechanical variables sensitive to half-marathon performance, which are essential to achieve high running speeds. However, when foot strike pattern and running speeds were controlled (submaximal test), the spatio-temporal variables were similar. This indicates that foot strike pattern and running speed are responsible for spatio-temporal differences among runners of different performance level.

Accuracy of PARTwear Inertial Sensor and Optojump Optical Measurement System for Measuring Ground Contact Time During Running

Ammann, R, Taube, W, and Wyss, T. Accuracy of PARTwear inertial sensor and Optojump optical measurement system for measuring ground contact time during running. J Strength Cond Res 30(7): 2057-2063, 2016-The aim of this study was to validate the detection of ground contact time (GCT) during running in 2 differently working systems: a small inertial measurement sensor, PARTwear (PW), worn on the shoe laces, and the optical measurement system, Optojump (OJ), placed on the track. Twelve well-trained subjects performed 12 runs each on an indoor track at speeds ranging from 3.0 to 9.0 m·s. GCT of one step per run (total 144) was simultaneously obtained by the PW, the OJ, and a high-speed video camera (HSC), whereby the latter served as reference system. The sampling rate was 1,000 Hz for all methods. Compared with the HSC, the PW and the OJ systems underestimated GCT by -1.3 ± 6.1% and -16.5 ± 6.7% (p-values ≤ 0.05), respectively. The intraclass correlation coefficients between PW and HSC and between OJ and HSC were 0.984 and 0.853 (p-values < 0.001), respectively. Despite the constant systematic underestimation of GCT, analyses indicated that PW successfully recorded GCT over a wide range of speeds. However, results showed only moderate validity for the OJ system, with increasing errors when speed decreased. In conclusion, the PW proved to be a highly useful and valid application, and its use can be recommended not only for laboratory settings but also for field applications. In contrast, data on GCT obtained by OJ during running must be treated with caution, specifically when running speed changes or when comparisons are made with GCT data collected by other measurement systems.

Agreement Between Face-to-Face and Free Software Video Analysis for Assessing Hamstring Flexibility in Adolescents

The objective of this study was to determine the level of agreement between face-to-face hamstring flexibility measurements and free software video analysis in adolescents. Reduced hamstring flexibility is common in adolescents (75% of boys and 35% of girls aged 10). The length of the hamstring muscle has an important role in both the effectiveness and the efficiency of basic human movements, and reduced hamstring flexibility is related to various musculoskeletal conditions. There are various approaches to measuring hamstring flexibility with high reliability; the most commonly used approaches in the scientific literature are the sit-and-reach test, hip joint angle (HJA), and active knee extension. The assessment of hamstring flexibility using video analysis could help with adolescent flexibility follow-up. Fifty-four adolescents from a local school participated in a descriptive study of repeated measures using a crossover design. Active knee extension and HJA were measured with an inclinometer and were simultaneously recorded with a video camera. Each video was downloaded to a computer and subsequently analyzed using Kinovea 0.8.15, a free software application for movement analysis. All outcome measures showed reliability estimates with α > 0.90. The lowest reliability was obtained for HJA (α = 0.91). The preliminary findings support the use of a free software tool for assessing hamstring flexibility, offering health professionals a useful tool for adolescent flexibility follow-up.

Reliability of video-based identification of footstrike pattern and video time frame at initial contact in recreational runners

INTRODUCTION

Two-dimensional video recordings are used in clinical practice to identify footstrike pattern. However, knowledge about the reliability of this method of identification is limited.

OBJECTIVE

To evaluate intra- and inter-rater reliability of visual identification of footstrike pattern and video time frame at initial contact during treadmill running using two-dimensional (2D) video recordings.

METHODS

Thirty-one recreational runners were recorded twice, 1 week apart, with a high-speed video camera. Two blinded raters evaluated each video twice with an interval of at least 14 days.

RESULTS

Kappa values for within-day identification of footstrike pattern revealed intra-rater agreement of 0.83-0.88 and inter-rater agreement of 0.50-0.63. Corresponding figures for between-day identification of footstrike pattern were 0.63-0.69 and 0.41-0.53, respectively. Identification of video time frame at initial contact ranged from five frames to 12 frames (95% limits of agreement).

CONCLUSION

For clinical use, the intra-rater within-day identification of footstrike pattern is highly reliable (kappa>0.80). For the inter-rater between-day identification inconsistencies may, in worst case, occur in 36% of the identifications (kappa=0.41). The 95% limits of agreement for identification of video time frame at initial contact may, at times, allow for different identification of footstrike pattern. Clinicians should, therefore, be encouraged to continue using clinical 2D video setups for intra-rater identification of footstrike pattern, but bear in mind the restrictions related to the between day identifications.

Rearfoot striking runners are more economical than midfoot strikers

PURPOSE

This study aimed to analyze the influence of foot strike pattern on running economy and biomechanical characteristics in subelite runners with a similar performance level.

METHODS

Twenty subelite long-distance runners participated and were divided into two groups according to their foot strike pattern: rearfoot (RF, n = 10) and midfoot (MF, n = 10) strikers. Anthropometric characteristics were measured (height, body mass, body mass index, skinfolds, circumferences, and lengths); physiological (VO2max, anaerobic threshold, and running economy) and biomechanical characteristics (contact and flight times, step rate, and step length) were registered during both incremental and submaximal tests on a treadmill.

RESULTS

There were no significant intergroup differences in anthropometrics, VO2max, or anaerobic threshold measures. RF strikers were 5.4%, 9.3%, and 5.0% more economical than MF at submaximal speeds (11, 13, and 15 km·h respectively, although the difference was not significant at 15 km·h, P = 0.07). Step rate and step length were not different between groups, but RF showed longer contact time (P < 0.01) and shorter flight time (P < 0.01) than MF at all running speeds.

CONCLUSIONS

The present study showed that habitually rearfoot striking runners are more economical than midfoot strikers. Foot strike pattern affected both contact and flight times, which may explain the differences in running economy.