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Improving running economy through altered shoe bending stiffness across speeds
Abstract
Increasing the longitudinal bending stiffness of running shoes decreases energy cost until a low point is reached, suggesting an optimal shoe stiffness. Previous research found optimal stiffness varies among individuals, however, none has determined the causes of variation both between individuals and running speeds. The primary purpose of this study was to understand how optimal shoe stiffness is affected by running speed. A secondary purpose examined the anatomical and biomechanical characteristics associated with optimal stiffness variation. Six shoe stiffness conditions were manufactured with a carbon fibre plate between the midsole and outsole of a standard running shoe. Twenty-one male runners (mass = 67.1 ± 5.0 kg, height = 178.9 cm ± 4.0 cm, age = 26.4 ± 8.4 years) completed testing at 2.98 m/s and 4.47 m/s in all shoe conditions, measuring metabolic cost, and several biomechanical and anatomical variables. Data were separated by foot strike. At the fast speed, average optimal stiffness was 19.29 ± 5.62 N/mm with a metabolic benefit of 3.02 ± 2.62%. Slow speed average optimal stiffness was 17.04 ± 6.09 N/mm with a metabolic benefit of 1.93 ± 1.82%. Only rearfoot strikers demonstrated a significant increase in optimal stiffness (p = .04) across speeds. There were no correlations between any of the measured anatomical or biomechanical variables and optimal stiffness. Optimal stiffness varied between subjects but was not correlated to any of our measured characteristics. Rearfoot striking runners may benefit from a higher stiffness shoe at faster speeds to enable optimal performance.
... In addition, researchers have also investigated the sine qua non conditions for observing meaningful improvements in running efficiency. While previous studies investigated the independent roles of foam resiliency (Flores et al., 2019;Worobets et al., 2014), sole curvature (Freitag et al., 2023;Nigg et al., 2020), and longitudinal bending stiffness (LBS) (Flores et al., 2019;Healey & Hoogkamer, 2022), others focused on the effect of running speed (Day & Hahn, 2021;McLeod et al., 2020) and distance (Kiesewetter et al., 2022). More recently, the role of the runners' profile (e.g. ...
... This agrees with previous studies having observed that an approximately 60% increase in LBS, achieved through the embedding of a carbon plate, did not affect running economy when running at 14-16 km/h (Healey & Hoogkamer, 2022;Perrin et al., 2023). Note that it is challenging to compare the absolute values of LBS across studies because of the lack of consistency and normalisation of the mechanical testing procedures (Chollet et al., 2023;Healey & Hoogkamer, 2022;Hoogkamer et al., 2019;McLeod et al., 2020;Perrin et al., 2023). Otherwise, an average 2% impairment of running economy was observed when LBS increased in uphill running. ...
... Otherwise, an average 2% impairment of running economy was observed when LBS increased in uphill running. Previous studies demonstrated that the effect of LBS is speed-dependent (Chollet et al., 2023;Day & Hahn, 2021;McLeod et al., 2020). In other words, high bending stiffness would exhibit its greatest benefit at the fastest speeds. ...
The emergence of carbon-plated trail running footwear has spurred a re-evaluation of their effects on metabolic power and joint biomechanics. This study investigates the influence of increased longitudinal bending stiffness (LBS) on these parameters during uphill running and on irregular terrain. Ten amateur trail runners wore two conditions of footwear: with and without carbon plates. For each condition, metabolic power was assessed on level and uphill treadmill running (11.6 ± 1.2 km/h and 7.8 ± 0.6 km/h, respectively), while 3D kinematics and kinetics of
lower limb joints were evaluated in a laboratory setting on unstable terrain. Subjective assessment of plantar feedback during running on irregular terrain was collected. Regarding biomechanics, discrete variables were extracted as surrogates for joint control on unstable terrains (e.g. normalised jerks, frontal peak angles, and ranges of motion). Because there is no consensus on the quantification of joint stability, the biomechanical analysis was completed with Bayesian statistical parametric mapping to depict differences in-between shoe conditions over the entire signals. Results revealed no footwear effect on metabolic power on level terrain but showed an increase in uphill running metabolic power with the plated condition (2 ± 2%, p = .04). No differences were observed in biomechanical parameters or plantar feedback between conditions. These findings suggest that while increasing LBS does not affect metabolic power during level running, it leads to performance degradation during uphill running. Therefore, the benefits of
increased LBS may not be applicable to technical trail running scenarios where running paces are very low. Embedding carbon plates in trail running footwear may lack physiological or biomechanical advantage, underscoring the necessity of considering contextual factors in footwear design for specific activities.
... An important consideration is that running economy and performance gains due to footwear can vary between individuals, with some individuals being 'high-responders' and some experiencing little to no gains (i.e., 'non-responders') (Hoogkamer et al., 2016;Hunter et al., 2019;McLeod et al., 2020;Stefanyshyn & Fusco, 2004). This individualised shoe response highlights how shoe technology can considerably disadvantage non-responders, making it critical for governing bodies to provide regulations to maintain fairness and integrity based on empirical evidence, particularly at the elite level where small differences can transform a race. ...
... The lower metabolic cost recorded in the prototype Vaporfly shoes was instead linked to the lower positive and negative work at the ankle indicative of lesser triceps surae muscle involvement . Although the benefit of increased longitudinal bending stiffness on running economy is, on average, clear (Rodrigo-Carranza et al., 2021); there are numerous moderating factors to consider and optimal shoe stiffness varies between individuals (McLeod et al., 2020;Nagahara et al., 2018;Smith et al., 2016;Stefanyshyn & Fusco, 2004;Willwacher et al., 2016), leading to some authors recommending personalised shoe stiffness (McLeod et al., 2020;Stefanyshyn & Fusco, 2004). Like shoe mass (Fuller et al., 2015), there may be a threshold beyond which additional longitudinal bending stiffness does not provide further running economy or performance gains. ...
... The lower metabolic cost recorded in the prototype Vaporfly shoes was instead linked to the lower positive and negative work at the ankle indicative of lesser triceps surae muscle involvement . Although the benefit of increased longitudinal bending stiffness on running economy is, on average, clear (Rodrigo-Carranza et al., 2021); there are numerous moderating factors to consider and optimal shoe stiffness varies between individuals (McLeod et al., 2020;Nagahara et al., 2018;Smith et al., 2016;Stefanyshyn & Fusco, 2004;Willwacher et al., 2016), leading to some authors recommending personalised shoe stiffness (McLeod et al., 2020;Stefanyshyn & Fusco, 2004). Like shoe mass (Fuller et al., 2015), there may be a threshold beyond which additional longitudinal bending stiffness does not provide further running economy or performance gains. ...
Advancements in running shoe technology over the last 5 years have sparked controversy in athletics as linked with clear running economy and performance enhancements. Early debates mainly surrounded ‘super shoes’ in long-distance running, but more recently, the controversy has filtered through to sprint and middle-distance running with the emergence of ‘super spikes’. This Current Concepts paper provides a brief overview on the controversial topic of super shoes and super spikes. The defining features of technologically advanced shoes are a stiff plate embedded within the midsole, curved plate and midsole geometry, and lightweight, resilient, high-energy returning foam that – in combination – enhance running performance. Since the launch of the first commercially available super shoe, all world records from the 5 km to the marathon have been broken by athletes wearing super shoes or super spikes, with a similar trend observed in middle-distance running. The improvements in super shoes are around 4% for running economy and 2% for performance, and speculatively around 1% to 1.5% for super spikes. These enhancements are believed multifactorial in nature and difficult to parse, although involve longitudinal bending stiffness, the ‘teeter-totter effect’, the high-energy return properties of the midsole material, enhanced stack height and lightweight characteristic of shoes.
... Thus, several LBS were suitable to several groups of runners with similar MTP stiffnesses. Cigoja et al. 17 and McLeod et al. 21 identified an individual optimal LBS based on running economy measurements, but they did not highlight any explanatory variables. Madden et al. 13 and Flores et al. 22 reported participant-specific benefits of an increased shoe LBS associated with biomechanical changes induced by an increased LBS. ...
... Based on the assumption from Cigoja et al., 24 it was hypothesised that an increased shoe LBS would limit and/or delay the increase in metabolic energetic demand. As highlighted in numerous studies, 12,13,17,[20][21][22] it was expected that the benefits induced by an increased shoe LBS would also be participant-specific, especially according to individual characteristics and/or biomechanical changes induced by an increased LBS relative to their shoe habits. ...
... The observed individual variability was in line with several studies highlighting participant-specific effects of the shoe LBS according to the task characteristics, 18 participants' characteristics 12,20 and biomechanics. 13,21,22 In the current study, correlation analyses were used on individual variations induced by an increased shoe LBS to highlight such potential associations. For the participants in the present study, an increased LBS mainly induced unclear (5 out of 11 runners) and detrimental (4 out of 11 runners) metabolic effects. ...
This study analysed the effects of increasing the longitudinal bending stiffness (LBS) of runners’ habitual shoes on the metabolic energetic demand, lower limb muscle activation and stride spatiotemporal parameters during a prolonged running session through classical group investigation, as well as a more individualised approach. Eleven recreational male participants ran overground for 40 min at 95% of their ventilatory anaerobic threshold with their own shoes or their shoes with higher LBS (stiff carbon plate inserted under insole). The net energetic cost of running, lower leg muscle activation and spatiotemporal parameters were measured during the prolonged running. The variables of interest were analysed for 1 min in seven time intervals. There were no main effects of LBS or interaction effects with running duration on the group averaged variables. Overall, the participant-specific metabolic effects induced by an increased shoe LBS were not beneficial. Beneficial metabolic effects were more likely to occur when the increased LBS induced a decrease or no change in the ground contact time relative to their habitual shoes, as well as for taller runners. Increasing the LBS in runners’ habitual shoes did not induce systematic metabolic effects for all the runners and may not be beneficial for performance purposes if the runners’ shoe habits were too disrupted.
... Currently, there is no standard method of measuring longitudinal bending stiffness of footwear. The most commonly used test is the three-point bending test [18][19][20][21][22][23], but torsional tests [5] and custom setups [24] have also been used. Even when the same setup is used, displacement ranges, measurement ranges, loading rates, and the number of loading cycles often differ between studies. ...
... Since then, studies have reported mixed results for the effects of increased longitudinal bending stiffness on RE ranging from small deteriorations [24], to no difference [19,21,23], to small (~ 1%) improvements [18,20], to more substantial (3-4%) improvements [5,8,9,22] (Table 2, see Electronic Supplementary Material Appendix S1 Table S2 for 1-page table and Electronic Supplementary Material Appendix S2 for all information reported in this article combined in a single table). ...
... There have been three main locations the plate has commonly been placed: (1) top loaded (plate placed as an insole or just below it); (2) embedded (in between midsole foam); (3) bottom loaded (along the sole of the shoe). There appears to be a distinction between studies that used embedded carbon-fiber plates and reported significant improvements in RE [18,22], and studies that use top-loaded plates, and did not find overall significant RE improvements [20,21,23,24]. Specifically, Flores et al. [21] and Beck et al. [23] both used top-loaded plates of similar longitudinal bending stiffness as the Vaporfly shoes, and while both studies controlled for mass, they did not observe improvements in RE as compared to control shoes. ...
In the wake of the quest to break the 2-h marathon barrier, carbon-fiber plates have become commonplace in marathon racing shoes. Despite the controversy surrounding this shoe technology, studies on the effects of increased longitudinal bending stiffness on running economy report mixed results. Here, we provide a comprehensive review of the current literature on midsole bending stiffness and carbon-fiber plates in distance running shoes, focusing on how longitudinal bending stiffness affects running energetics and lower limb mechanics. The current literature reports changes in running economy with increased longitudinal bending stiffness ranging from ~ 3% deterioration to ~ 3% improvement. In some studies, larger improvements have been observed, but often those shoes varied in many aspects, not just longitudinal bending stiffness. Biomechanically, increased longitudinal bending stiffness has the largest impact on metatarsal–phalangeal (MTP) and ankle joint mechanics. Plate location [top loaded (an insole), embedded (in between midsole foam), and bottom loaded (along the bottom of the shoe)] and geometry (flat/curved) affect joint moments and angular velocities at the MTP and ankle joint differently, which partly explains the mixed running economy results. Further research investigating how carbon-fiber plates interact with other footwear features (such as foam and midsole geometry), scaling of those with shoe size, body mass, and strike pattern, and comparing various plate placements is needed to better understand how longitudinal bending stiffness affects running economy.
... Energy storage and return of the ankle plantar flexor complex and the subsequent influence on metabolic cost may also be affected by altered ankle plantar flexor moments in response to increased LBS [4]. Prior research has suggested that longitudinally stiffer shoes improve running economy at faster speeds [8,9]. Investigation into joint-level mechanics changes may reveal a potential mechanism as to why. ...
... With such a mechanical re-organization of how we run at faster speeds, there may be speed dependent changes in joint level mechanics to altered LBS. These changes may help explain speed-dependent changes in running economy to footwear stiffness [8,9]. ...
... Lastly, participant recruitment was not limited to rearfoot strike runners only. Altering LBS may affect forefoot and rearfoot strike runners differently [9]. ...
Background
Modifying the longitudinal bending stiffness (LBS) of footwear has become a popular method to improve sport performance. It has been demonstrated to influence running economy by altering lower extremity joint level mechanics. Previous studies have only examined within-participant effects at one running speed.
Research Question
Do joint level mechanics differ in response to varying footwear LBS at a range of running speeds?.
Methods
This study utilized a cross-sectional repeated measure study design using a convenience sample. Ten well trained non-rearfoot strike male distance runners ran at 3.89, 4.70, and 5.56 m/s (14, 17, 20 km/hr) in footwear of three different LBS levels. Mechanics and energetics of the metatarsophalangeal joint (MTPJ), ankle, knee, and hip joints during stance phase were assessed using an 8-camera optical motion capture system (fs =200 Hz), a force instrumented treadmill (fs =1000 Hz) and standard inverse dynamics theory.
Results
Range of motion and negative work decreased and angular stiffness increased for the MTPJ with increasing LBS at all speeds (p < .001). Peak MTPJ moment did not change at any speed in response to increased LBS. Negative work at the ankle decreased in the stiff shoe at 17 km/hr (p = .036). Peak ankle plantar flexion velocity decreased with increasing LBS at all speeds (p < .05).
Significance
While changes in MTPJ mechanics were consistent across speeds, decreased negative ankle work was only observed at 17 km/hr in the stiff shoe, suggesting that perhaps tuned footwear LBS may need to focus primarily on metabolically beneficial changes in ankle plantar flexor mechanical behavior to improve performance in distance runners. Tuning footwear stiffness may also be beneficial to clinical populations, as clinicians seek to optimize their patients’ locomotion economy.
... These views persist even though it is inconclusive whether adding carbon fiber to shoe soles improves running economy [12][13][14][15][16] or distance-running performance. To date, two studies have reported that adding optimally stiff carbon fiber plates to shoe soles improves running economy by 0.8 12 and 1.1% 13 , while data from four other studies suggest that adding carbon fiber plates to shoe soles does not affect running economy [14][15][16][17] . ...
... How does adding carbon fiber plates to shoe soles affect athlete plantar flexor dynamics during running? Adding carbon fiber plates to shoe soles increases the footwear's 3-point bending stiffness 12,13,15,17,24,25,28 and typically shifts the athlete's center of pressure more anterior along the foot during ground contact 24,25,28,29 . These altered biomechanics generally yield a longer moment arm between the ground reaction force (F GRF ) and the ankle-joint center ( R GRF ) 13,24 . ...
... In particular, we sought to investigate how footwear 3-point bending stiffness affects soleus fascicle dynamics and running economy. Based on the reported interactions between adding carbon fiber plates to shoe soles, footwear 3-point bending stiffness [12][13][14][15]17,24,25,28,29 , and ankle-joint dynamics 13,14,24,29 , we hypothesized that running with shoes that have stiffer carbon fiber plates would increase soleus fascicle force generation while decreasing its operating length and shortening velocity during the ground contact. We also hypothesized that an optimal footwear bending stiffness would minimize soleus active muscle volume and aerobic energy expenditure. ...
In an attempt to improve their distance-running performance, many athletes race with carbon fiber plates embedded in their shoe soles. Accordingly, we sought to establish whether, and if so how, adding carbon fiber plates to shoes soles reduces athlete aerobic energy expenditure during running (improves running economy). We tested 15 athletes as they ran at 3.5 m/s in four footwear conditions that varied in shoe sole bending stiffness, modified by carbon fiber plates. For each condition, we quantified athlete aerobic energy expenditure and performed biomechanical analyses, which included the use of ultrasonography to examine soleus muscle dynamics in vivo. Overall, increased footwear bending stiffness lengthened ground contact time (p = 0.048), but did not affect ankle (p ≥ 0.060), knee (p ≥ 0.128), or hip (p ≥ 0.076) joint angles or moments. Additionally, increased footwear bending stiffness did not affect muscle activity (all seven measured leg muscles (p ≥ 0.146)), soleus active muscle volume (p = 0.538; d = 0.241), or aerobic power (p = 0.458; d = 0.04) during running. Hence, footwear bending stiffness does not appear to alter the volume of aerobic energy consuming muscle in the soleus, or any other leg muscle, during running. Therefore, adding carbon fiber plates to shoe soles slightly alters whole-body and calf muscle biomechanics but may not improve running economy.
... Only limited research is currently available on how AFT influences the performance of recreational runners. McLeod et al. (2020) examined different levels of longitudinal bending stiffness (LBS) across a faster and slower speed, on runners able to complete a 10 km run in under 36 min, finding that for a group of 10 rearfoot strikers the optimal stiffness was higher at the faster speed. also examined the influence of LBS across trained (10 km time 38:51 ± 0:51 mm:ss) and national (31:51 ± 0:53 mm:ss) level runners, they found that the increased stiffness resulted in improved running economy at both slow and fast speeds for the trained runner, and only at fast speed in national runners. ...
... Previous research has been conducted on different shoe sizes (Barnes & Kilding, 2019;Hébert-Losier et al., 2020;Hunter et al., 2019;McLeod et al., 2020). However, the majority of research has focused mainly on male runners, with only Reynolds et al. (2023) and Barnes and Kilding (2019) using female participants. ...
... Few addressed individual responses to changes in longitudinal bending stiffness, and the existence of these individual responses remains largely unexplained. In regard to previous findings (Oh and Park 2017;Flores et al. 2019;McLeod et al. 2020;Madden et al. 2016), it is worth to analyze the relationship between physiological responses, increased bending stiffness, and runners' characteristics (e.g., anthropometrics, biomechanics, etc.). In addition, studying the effect of bending stiffness on RE in a wider population of runners is of interest for shoe manufacturers aiming at developing footwear for very different profiles of participants. ...
... Furthermore, recent studies have highlighted the notion of optimal stiffness. The term optimal stiffness describes the bending stiffness permitting to minimize RE. McLeod et al. (McLeod et al. 2020) showed that this optimal stiffness would depend on the runner's speed and running pattern. Moreover, Oh and Park. ...
Background:
Shoe longitudinal bending stiffness is known to influence running economy (RE). Recent studies showed divergent results ranging from 3% deterioration to 3% improvement in RE when bending stiffness increases. The variability of these results highlights inter-individual differences. Thus, our purpose was to study the runner-specific metabolic responses to changes in shoe bending stiffness.
Methods:
After assessing their maximal oxygen consumption ([Formula: see text] max) and aerobic speed (MAS) during a first visit, 96 heterogeneous runners performed two treadmill 5 min runs at 75% [Formula: see text] max with two different prototypes of shoes on a second day. Prototypes differed only by their forefoot bending stiffness (17 N/mm vs. 10.4 N/mm). RE and stride kinematics were recorded during each trial. A clustering analysis was computed by comparing the measured RE and the technical measurement error of our gas exchange analyzer to identify functional groups of runners, i.e., responding similarly to footwear interventions. ANOVAs were then computed on biomechanical and morphological variables to compare the functional groups.
Results:
Considering the whole sample (n = 96), there was no significant difference in RE between the two conditions. Cluster 1 (n = 29) improves RE in the stiffest condition (2.7 ± 2.1%). Cluster 2 (n = 26) impairs RE in the stiffest condition (2.7 ± 1.3%). Cluster 3 (n = 41) demonstrated no change in RE (0.28 ± 0.65%). Cluster 1 demonstrated 1.7 km·h-1 greater MAS compared to cluster 2 (p = 0.014).
Conclusion:
The present study highlights that the effect of shoe bending stiffness on RE is runner-specific. High-level runners took advantage of increased bending stiffness, whereas medium-level runners did not. Finally, this study emphasizes the importance of individual response examination to understand the effect of footwear on runner's performance.
... This would suggest that the benefits of the shoes may be relatively speed agnostic. However, slower speeds do have distinct effects on the kinetic and spatiotemporal characteristics of a runner's gait (McMahon & Cheng, 1990;Nilsson & Thorstensson, 1989) and may affect the runner's response to footwear with altered longitudinal bending stiffness (LBS; McLeod et al., 2020;Day and Hahn, 2020). How the substantially slower speeds may interact with the novel features of the shoes-the greater volume of compliant, resilient foam and the stiff, curved carbon fiber plate-is unknown. ...
... Rearfoot striking runners have also demonstrated higher optimal longitudinal bending stiffnesses at 16.1 km·hr -1 vs. 10.4 km·hr -1 (McLeod et al., 2020). The role of the rigid plate in the observed energetic benefit of modern super shoes is still being elucidated , but these limited studies would suggest that the characteristically higher LBS in these super shoes might favor faster speeds for some individuals. ...
... In 2006, Roy and Stefanyshyn 16 showed small (1%) improvements in running economy with increased LBS. However, since then, reported effects of LBS on running economy have been mixed, with studies finding results ranging from deteriorations 18 , to no effect [19][20][21] , to small effect (~1%) 22 to large improvements (3%4%) [8][9][10][11]23 (for a full review, see Ortega et al 24 ). ...
... Supporting our third hypothesis, MTP joint dorsiflexion angle and power were significantly larger in the VF cut ; however, MTP joint moment was not significantly different between conditions.Our findings are in line with previous research finding small differences in running economy between shoes with and without carbon-fiber plates. 16,19,22,23 However, most of these studies used flat plates, and we hypothesized that the curved plate in the VF would result in additional savings and explain ~2% of the 4% savings reported by Hoogkamer et al. 8 ...
Objective:
To determine the independent effect of the curved carbon-fiber plate in the Nike Vaporfly 4% shoe on running economy and running biomechanics.
Methods:
Fifteen healthy male runners completed a metabolic protocol and a biomechanics protocol. In both protocols participants wore 2 different shoes, an intact Nike Vaporfly 4% (VFintact) and a cut Nike Vaporfly 4% (VFcut). The VFcut had 6 medio-lateral cuts through the carbon-fiber plate in the forefoot to reduce the effectiveness of the plate. In the metabolic protocol, participants ran at 14 km/h for 5 min, twice with each shoe, on a force-measuring treadmill while we measured metabolic rate. In the biomechanics protocol, participants ran across a runway with embedded force plates at 14 km/h. We calculated running economy, kinetics, and lower limb joint mechanics.
Results:
Running economy did not significantly differ between shoe conditions (on average, 0.55% ± 1.77% (mean ± SD) worse in the VFcut compared to the VFintact; 95% confidence interval: (-1.44% to 0.40%)). Biomechanical differences were only found in the metatarsophalangeal joint (MTP) with increased MTP dorsiflexion angle, angular velocity, and negative power in the VFcut. Contact time was 1% longer in the VFintact.
Conclusion:
Cutting the carbon-fiber plate and reducing the longitudinal bending stiffness did not have a significant effect on the energy savings in the Nike Vaporfly 4%. This suggests that the plate's stiffening effect on the MTP joint plays a limited role in the reported energy savings, and instead savings are likely from a combination and interaction of the foam, geometry, and plate.
... More recent studies focused on investigating potential relationships between midsole bending stiffness and running speed (Day & Hahn, 2020;McLeod, Bruening, Johnson, Ward, & Hunter, 2020 Furthermore, potential relationships between anatomical and biomechanical characteristics and best performing midsole bending stiffness were compared. The main findings of the study were that, on average, the best stiffness was ~13% higher when running at the faster speed (i.e., 16.09 km•h -1 ) compared to the slower speed (i.e., 10.73 km•h -1 ). ...
... Therefore, the authors conclusion that the midsole bending stiffness of running shoes likely needs to be adjusted based on a runner's speed is difficult to justify based on the provided results and explanations. Similarly,McLeod et al. (2020) investigated if different levels of midsole bending stiffness are needed to improve running economy at different speeds. ...
The latest records set during long-distance running competitions have been attributed to recent footwear midsole innovations. One of these midsole innovations that has been claimed to have large effects on biomechanical, physiological, and performance variables is the use of a carbon fibre plate to increase the longitudinal bending stiffness of a shoe. Several mechanisms were proposed to be associated with performance improvements when running in footwear with carbon fibre plates. One of these mechanisms, the principle of optimising muscle function is currently not well understood. Therefore, this thesis aimed to investigate the effects of midsole bending stiffness of athletic footwear on muscle and muscle-tendon unit function in running. The first part of this thesis showed that running in stiff footwear resulted in a redistribution of positive work from proximal to distal lower limb joints. Specifically, it was found that a fatigue-induced redistribution of joint work from distal to proximal joints can be delayed when running in stiff footwear. The second part of this thesis dealt with the shortening velocities of muscle-tendon units. Estimated shank muscle-tendon unit shortening velocities were reduced when running in stiffer shoes. Experimental results using ultrasound imaging of the gastrocnemius medialis muscle revealed that the muscle shortened to a lesser extent and with lower average velocities in stiff running footwear. These findings could have implications for long-distance running performance. Positive work generation at more distal joints (i.e., ankle) may result in lower active muscle volume, which has been shown to be the main determinant of changes in the energetic cost of running. Slower shortening velocities of the gastrocnemius medialis could allow the muscle to operate on a more favourable position on its force-velocity relationship. This could allow for more economical force generation for a longer period during long-distance running. Altered muscle function could be a source of improved performance when running in stiff shoes.
... In 2006, Roy and Stefanyshyn 12 showed small (1%) improvements in running economy with increased LBS. However, since then, reported effects of LBS on running economy have been mixed, with studies finding deteriorations 14 , no effect [15][16][17] , or small (~1%) 12,18 , to large improvements (3-4%) 1,7,8,19 (for review see 20 ). Importantly, the largest improvements in running economy have been reported in studies assessing VF shoes 1,7,8 , suggesting that the geometry and stiffness of the curved VF plate may provide additional savings compared to flat plates previously tested. ...
... Our findings are in line with previous research finding small differences in running economy between shoes with and without carbon-fiber plates 12,15,18,19 . However, most of these studies used flat plates, and we hypothesized the curved plate in the VF would result in additional savings and explain ~2% of the 4% savings reported by Hoogkamer et al. 1 These results challenge the recent suggestion that a curved plate alone can provide metabolic savings as high as 6% by acting as a teeter-totter 2,13 . ...
Objectives: To determine the independent effect of the curved carbon-fiber plate in the Nike Vaporfly 4% shoe on running economy and running biomechanics.Methods: Fifteen healthy male runners completed a metabolic protocol and a biomechanics protocol. In both protocols participants wore two different shoe conditions, an intact Nike Vaporfly 4% (VFintact), and a cut Nike Vaporfly 4% (VFcut). The VFcut had 6 medio-lateral cuts through the carbon-fiber plate in the forefoot to reduce the effectiveness of the plate. In the metabolic protocol participants ran at 14 km/h for 5-minutes, twice with each shoe, on a force-measuring treadmill while breathing into an expired gas system. In the biomechanics protocol participants ran across a runway with embedded force plates at 14 km/h. We calculated running economy, kinetics, and joint mechanics of the lower limb.Results: Running economy did not significantly differ between shoe conditions (0.5% higher in the VFcut compared to the VFintact). Biomechanical differences were only found in the metatarsophalangeal joint (MTP) with increased MTP dorsiflexion angle, angular velocity, and negative power in the VFcut. Contact time was 1% longer in the VFcut.Conclusion: Cutting the carbon-fiber plate and reducing the longitudinal bending stiffness did not have a significant effect on the energy savings in the Nike Vaporfly 4%. This suggests that the plate alone plays a limited role in the 4% energy savings, and instead those likely result from a combination and interaction of the foam, geometry, and plate.
... This is particularly relevant for spikes as benefits from footwear are likely to be speed specific. 12 To overcome this challenge, we recently introduced and validated a novel approach to assessing the benefits of AFT spikes, consisting of a series of 200-m trials at a self-perceived middledistance (800 m or mile) race pace on the track. 13 Two other tools are commonly used to assess the benefits of AFT spikes for longer races: 3000-to 5000-m time trials and RE measurements. ...
Purpose : Two new designs of track spikes have recently emerged: spikes with a compliant and resilient midsole foam (eg, polyether block amide [PEBA]) and spikes that combine such modern foam with a carbon fiber plate. We evaluated the effect of these different spikes on running performance measures for middle- and long-distance track events in trained runners. Methods : Fourteen females on a single visit performed six 200-m trials at a self-perceived 800-m race pace in 3 different spike conditions (Control, PEBA, and PEBA + Plate), twice in a mirrored order. Sixteen males completed 4 visits. During each of the first 3 visits, they performed six 200-m trials at a self-perceived 800-m race pace, twice in each condition, followed by a 3000-m time trial in 1 of the 3 spike conditions. During visit 4, participants completed six 4-minute running-economy trials at 5 m/s, twice in each condition. Results : At the 800-m race pace, females ran faster in PEBA (2.1%) and PEBA + Plate (2.0%) compared with Control. Males ran faster in PEBA (1.4%) and PEBA + Plate (2.4%) compared with Control and in PEBA + Plate compared with PEBA (1.1%). Similarly, males ran the 3000-m time trial faster in PEBA (1.0%) and PEBA + Plate (2.4%) than in Control. Running economy was better in PEBA (5.1%) and PEBA + Plate (4.0%) than in Control. Conclusions: Compared with traditional spiked shoes, shoes with PEBA foam (both with and without a plate) enhanced distance-running performance measures by 1% to 2% in females and males, with greater benefits in the PEBA + Plate condition in males.
... Advanced footwear technology (AFT) [1] provides substantial improvements in running economy [2] and performance [3], but there is still much debate about the relative contribution of the different shoe properties involved, including shoe mass [4], compliance [5], resilience [6], and longitudinal bending stiffness [7]. As a result, there has been a resurgence of research on the topic. ...
... The initial loading method involved setting the stamping head to move 7.5 mm vertically downward at a rate of 75 mm/s over 0.1 s, with the center of the forefoot as the reference point [9]. Subsequently, the loading rate was adjusted in various studies to 15 mm/s [7], 500 mm/min (8.33 mm/s) [20], 16 mm/s [36], 4 mm/s [19], 12.5 mm/s [27], and 10 mm/s [26], with displacement ranges including 10 mm [18], 20 mm [19], and 15 mm [6]. Although the measurement ranges differ, all studies performed linear regression on the linear portion of the force-displacement curve [6,26,37]. ...
The forefoot longitudinal bending stiffness of shoe soles, measured through the widely used three-point bending test, is a key factor influencing running economy and lower-limb biomechanics. This study utilizes the finite element method to simulate three-point bending, examining the influence of different loading rates on stiffness and analyzing the impact of various plate thicknesses and forefoot curvature radii on the stiffness of plates and the ‘plate-sole’ system. The results indicate that within the same displacement range, varying the loading rates did not affect stiffness. However, increased thickness significantly enhanced both the stiffness of the plate and the ‘plate-sole’, while a larger curvature radius of the plate resulted in a modest 5–10% stiffness increase for both. To conclude, the present study provides a theoretical foundation for further exploring the mechanical properties of carbon plate configurations in footwear. Plate stiffness is affected by both thickness and curvature radius, with thickness having a greater impact. The same applies to the ‘plate-sole’. The stiffness of the ‘plate-sole’ is not a simple sum of the individual contributions from the shoe and the plate. This non-additive response emphasizes the significant role of the shoe material in altering the plate’s mechanical properties, which is an important consideration for optimizing shoe design.
... Reflective markers with a base diameter of 14 mm were directly attached to the participants' feet to accurately capture the MTP joint movements during running [28]. Subsequently, participants were required to run across the collection area at a speed of 4.47 m/s ± 5% [24], with the landing method chosen freely by the participants. A timing system was used to monitor speed, and GRF data were collected by a force plate (Kistler, Switzerland) located in the center of a 40-meter track at a frequency of 2000 Hz. ...
Purpose
The impacts of shoe stiffness on running biomechanics are well-documented, while the specific effects on the performance of biomechanically distinct groups such as novice runners and experienced runners are still largely unexplored. The study aimed to evaluate the biomechanical effects of different shoe longitudinal bending stiffness (adjusted by inserting carbon plate) on the lower limb during running in novice runners and experienced runners.
Methods
Twelve experienced runners and ten novice runners ran at a speed of 4.47 m/s while randomly wearing shoes with either low stiffness (5.9 Nm/rad) or high stiffness (8.6 Nm/rad). An Opensim musculoskeletal model was adopted for estimating lower limb joint angles, joint angular velocities, joint moment, joint work, peak joint reaction forces during running stance phase.
Results
Results showed that novice runners displayed greater lower limb joint mobility and less joint moment, while experienced runners exhibited less joint mobility but greater joint moment, and higher peak joint reaction forces were observed at the knee and ankle joints. Furthermore, increased shoe longitudinal bending stiffness resulted in higher peak joint reaction forces at the metatarsophalangeal joint for novice runners while lower for experienced runners.
Conclusions
Novice runners may face an increased risk of metatarsal pain or stress fractures when dealing with higher shoe stiffness. This nuanced understanding of joint dynamics underscores the need for tailored training and footwear recommendations to mitigate injury risks specific to different levels of running experience.
... To study the isolated effects of increased LBS on the RE, several studies have used baseline control shoes and modified LBS by embedding carbon-fiber plates in the midsole or using carbon-fiber insoles, keeping other properties (e.g., upper, midsole foam, and geometry) constant. There appears to be a distinction between studies that used embedded carbon-fiber plates and reported significant improvements in RE of around 1% [12][13][14] versus studies that used top-loaded plates (insoles) and did not find overall significant RE improvements [15][16][17][18]. Roy & Stefanyshyn [14] studied traditional running shoes with three different levels of LBS using flat carbon fiber plates embedded in the midsole for running on a treadmill at ~13.5 km/h. ...
Introduction/Purpose
Shoe longitudinal bending stiffness (LBS) is often considered to influence running economy (RE) and thus, running performance. However, previous results are mixed and LBS levels have not been studied in advanced footwear technology (AFT). The purpose of this study was to evaluate the effects of increased LBS from curved carbon fiber plates embedded within an AFT midsole compared to a traditional running shoe on RE and spatiotemporal parameters.
Methods
Twenty‐one male trained runners completed three times 4 min at 13 km/h with two experimental shoe models with a curved carbon fiber plate embedded in an AFT midsole with different LBS values (Stiff: 35.5 N/mm and Stiffest: 43.1 N/mm), and a Control condition (no carbon fiber plate: 20.1 N/mm). We measured energy cost of running (W/kg) and spatiotemporal parameters in one visit.
Results
RE improved for the Stiff shoe condition (15.71 ± 0.95 W/kg; p < 0.001; n² = 0.374) compared to the Control condition (16.13 ± 1.08 W/kg; 2.56%) and Stiffest condition (16.03 ± 1.19 W/kg; 1.98%). However, we found no significant differences between the Stiffest and Control conditions. Moreover, there were no spatiotemporal differences between shoe conditions.
Conclusion
Changes in LBS in AFT influences RE suggesting that moderately stiff shoes have the most effective LBS to improve RE in AFT compared to very stiff shoes and traditional, flexible shoe conditions while running at 13 km/h.
... It seems likely that the carbon fiber insoles employed in the present study did not possess enough longitudinal bending stiffness to have a robust impact on the running economy. Other studies suggest that optimal bending stiffness levels are individual (33,19) and speed-dependent (34,35). Therefore, a carbon insole with a single absolute bending behavior might not be suitable to improve running economy and performance in a group of runners with different strike patterns and body mass. ...
In a randomized controlled cross-over study ten male runners (26.7 ± 4.9 years; recent 5-km time: 18:37 ± 1:07 min:s) performed an incremental treadmill test (ITT) and a 3-km time trial (3-km TT) on a treadmill while wearing either carbon fiber insoles with downwards curvature or insoles made of butyl rubber (control condition) in light road racing shoes (Saucony Fastwitch 9). Oxygen uptake, respiratory exchange ratio, heart rate, blood lactate concentration, stride frequency, stride length and time to exhaustion were assessed during ITT. After ITT, all runners rated their perceived exertion, perceived shoe comfort and perceived shoe performance. Running time, heart rate, blood lactate levels, stride frequency and stride length were recorded during, and shoe comfort and shoe performance after, the 3-km TT. All parameters obtained during or after the ITT did not differ between the two conditions [range: p = 0.188 to 0.948 (alpha value: 0.05); Cohen's d = 0.021 to 0.479] despite the rating of shoe comfort showing better scores for the control insoles (p = 0.001; d = −1.646). All parameters during and after the 3-km TT showed no differences (p = 0.200 to 1.000; d = 0.000 to 0.501) between both conditions except for shoe comfort showing better scores for control insoles (p = 0.017; d = −0.919). Running with carbon fiber insoles with downwards curvature did not change running performance or any submaximal or maximal physiological or biomechanical parameter and perceived exertion compared to control condition. Shoe comfort is impaired while running with carbon fiber insoles. Wearing carbon fiber insoles with downwards curvature during treadmill running is not beneficial when compared to running with control insoles.
... Furthermore, there is currently limited knowledge regarding what the optimal AFT properties are for an individual runner (e.g., midsole stiffness, longitudinal bending stiffness, stack height, geometry). Factors such as running speed [12][13][14], foot strike pattern [3], contact time [4], body mass [15], plantar flexor strength [16,17], foot arch stiffness [18], joint range of motion [19], and training level [20] can be expected to play some role here, but the current body of scientific knowledge is insufficient to draw conclusions. ...
In the quest to uncover the underlying mechanisms responsible for the performance-enhancing benefits imparted by advanced footwear technology (AFT), footwear researchers are employing an individual-level approach. In doing so, they hope to unveil individual-specific responses to AFT otherwise masked by a group-level approach. Classifying an individual’s response on the basis of running economy (RE) is a logical strategy given that the intended purpose of AFT is to enhance performance; however, caution should be taken when doing so. Metabolic measurement devices are far from perfect, and given the known errors associated with metabolic measurements we would like to reiterate a suggestion first made 40 years ago: when seeking to quantify the interindividual variability of improvement in RE associated with running in AFT, the best practice is to rely on a minimum of two same-day measurements of RE.
... CX1AWnYQp/IlQrHD3i3D0OdRyi7TvSFl4Cf3VC1y0abggQZXdtwnfKZBYtws= on 02/21/2024 greater proportional metabolic consumption (14) compared to MTP joint flexors, reductions in ankle angular work (13) and reduced plantarflexion velocity during stance phase (9,15) seem to (7,13,(23)(24)(25), this hypothesis has not yet been explicitly studied. Hoogkamer et al. (2018) and Hébert-Losier et al. (2020) both showed greater metabolic savings in RFS runners compared to non-RFS runners in sub-analyses within their studies (i.e., not the main objective) but the mechanisms for these findings were not explicitly provided and further investigation was recommended. ...
Super-shoes” are designed to improve endurance running performance by reducing the metabolic demands of running. While the research on “super-shoes” is still developing and has mostly been studied in male runners, it is not clear how possible mediating factors, such as foot strike pattern, influence the metabolic cost and joint mechanics in competitive female runners.
Purpose
To assess the influence of “super-shoes” on metabolic cost and joint mechanics in competitive female runners, and to understand how foot strike pattern may influence the footwear effects.
Methods
Eighteen competitive female runners ran four 5-minute bouts on a force instrumented treadmill at 12.9 km·h ⁻¹ in: 1) Nike Vaporfly Next% 2 TM (SUPER) and 2) Nike Pegasus 38 TM (CON) in a randomized and mirrored order.
Results
Metabolic power was improved by 4.2% (p < 0.001; d = 0.43) and MTP negative work (p < 0.001; d = 1.22), ankle negative work (p = 0.001; d = 0.67), and ankle positive work (p < 0.001; d = 0.97) were all smaller when running in SUPER compared to CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percent change for metabolic power (r = 0.093, p = 0.715).
Conclusions
Metabolic power improved by 4.2% in “super-shoes” (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in “super-shoes” are consistent with previous literature and may explain or contribute to the metabolic improvements observed in “super-shoes”, however foot strike pattern was not a moderating factor for the metabolic improvements of “super-shoes”. Future studies should directly compare the metabolic response among different types of “super-shoes” between men and women.
... In this regard, there is an optimal individual LBS of shoe soles to improve running economy, taking into account factors such as running speed [49,50], individual natural MTPJ flexion [51] or weight [34,52]. However, Oh & Park [51] have shown that a sole with a stiffness close to the natural individual stiffness of the MTPJ can improve running economy by 1.1%. ...
This study highlights the need for a deeper understanding of the structure-property relationships of carbon fiber reinforced thermosets applications, whenever considered as a functional part for running footwear. This is done, investigating the static and dynamic flexural properties of three different epoxy resins in prepreg-based carbon fiber composite laminates, varying the glass transition temperature (Tg). In this way, the inherent morphology of the resin was correlated with the fatigue properties of the laminate, which is crucial for the design of composite stiffening inlays for running shoes. First, it was shown that the crosslink density and aromatic content of the resin, which correlates with Tg, drastically affect the compressive strength of the matrix and are therefore crucial for the static and dynamic flexural properties of CFRP. Increasing the Tg from 147 °C to 269 °C leads to stiffening of the resin and thus increased resistance to fiber buckling, resulting in improved bending stiffness, flexural strength, bending angle, overall fatigue strength and thus durability of CFRP plates for running shoes. Moreover, the percentage of fibers in the loading direction can be considered as the main factor affecting the flexural properties of the laminate. Here, a quasi-isotropic stacking order leads to an increased bending angle but to a decrease in bending stiffness, flexural strength and fatigue strength compared to a unidirectionally reinforced composite due to a high load bearing capacity of the 0° fibers. This knowledge creates a basis to bridging the gap between composite material and biomechanical sports science for future work.
... Similar to the aforementioned location effects, it appears there is a distinction between studies that investigated the effects of CFP thickness (stiffness) on RE. Some studies found that high stiff plate contributed to improved RE (Hoogkamer et al., 2018;McLeod et al., 2020) while others observed no improvement (Flores et al., 2019a) or even inferior running performance (Day and Hahn, 2020). Overall, it seems that the two discussed CFP variations could both influence the interfacial interactions among the foot, shoe, and ground, potentially leading to mixed running performance results. ...
A carbon-fiber plate (CFP) embedded into running shoes is a commonly applied method to improve running economy, but little is known in regard the effects of CFP design features on internal foot mechanics. This study aimed to explore how systematic changes in CFP geometrical variations (i.e., thickness and location) can alter plantar pressure and strain under the forefoot as well as metatarsal stress state through computational simulations. A foot-shoe finite element (FE) model was built and different CFP features including three thicknesses (1 mm, 2 mm, and 3 mm) and three placements (high-loaded (just below the insole), mid-loaded (in between the midsole), and low-loaded (just above the outsole)) were further modulated within the shoe sole. Simulations were conducted at the impact peak instant during forefoot strike running. Compared with the no-CFP shoe, peak plantar pressure and compressive strain under the forefoot consistently decreased when the CFP thickness increased, and the low-loaded conditions were found more effective (peak pressure decreased up to 31.91% and compressive strain decreased up to 18.61%). In terms of metatarsal stress, CFP designs resulted in varied effects and were dependent on their locations. Specifically, high-loaded CFP led to relatively higher peak metatarsal stress without the reduction trend as thickness increased (peak stress increased up to 12.91%), while low-loaded conditions showed a gradual reduction in peak stress, decreasing by 0.74%. Therefore, a low-loaded thicker CFP should be considered to achieve the pressure-relief effects of running shoes without the expense of increased metatarsal stress.
... Furthermore, the footwear industry and running culture constantly propagate the idea that specific running shoes can reduce injury risk and improve performance (e.g. force attenuation, running faster or farther) (Walton & French, 2016) despite the lack of research to substantiate these claims in relation to injury (Knapik et al., 2015) and the existence of individualized responses to footwear in terms of performance (H ebert-Losier et al., 2020;McLeod et al., 2020). As a result, runners face potential pitfalls, biases, and misinformation throughout the shoe selection process. ...
Running shoes are often considered essential to participate in running. Runners may look for recommendations from friends, specialty running stores, and healthcare professionals when selecting shoes. Despite the existence of shoe prescription guidelines, these recommendations are often not evidence-based or designed with runners’ preferences in mind. This review aims to synthesize original research that identifies how road runners select running shoes. Following PROSPERO registration (CRD42021242523), the PubMed®, Scopus®, Web of Science®, and SPORTDiscus™ electronic databases were systematically searched in March 2021, and monitored until 1 February 2022. Original research that identified factors influencing running shoe selection in road runners published in English were included. Data were qualitatively synthesized. Seven studies representing 1947 road runners were included, and conducted either online, in laboratories, or via interview. Forty influencing factors were identified and thematically sub-grouped into five categories: subjective, shoe-specific characteristics, market features, peer evaluation, and runner characteristics. Comfort, cushioning, fit, and price were cited most frequently as influential factors in road runners’ footwear selection. Most of the studies reviewed were not specifically designed to address the research question of this review. Lack of consistent definitions and varying research methods are found across studies. There is limited research targeting the factors that influence running shoe selection. Comfort and cushioning appear to be the most important factors in shoe selection, although the relationship between both variables may confound their individual importance. Runners also consider fit, price, and several other factors when selecting shoes. Shoe choice remains relatively unexplored, with no running shoe selection study conducted in store.
... Several studies have recently highlighted that the longitudinal bending stiffness of the shoes is associated with a decrease in running energy cost (Madden et al. 2016). More specifically, McLeod et al. (2020) have reported that shoe construction needs to be personalised in regard to longitudinal bending stiffness when running economy is valued. Consequently, the ability to measure foot muscle strength and particularly at the metatarsophalangeal (MTP) joint is necessary for researchers and shoe companies. ...
Studies show the high potential of shoes to impact human movement and reduce the risk of injuries during normal and high-demanding activities. This review will delve into the existing literature on mechanical and biomechanical tests of shoes and their effects on the human body. Mechanical tests mainly include compression, bending, torsional flexibility, and impact tests. Biomechanical tests, on the other hand, study the kinematics and kinetics of the human body while performing different tasks. The primary goal of this review is to highlight the importance of isolating parameters in shoe design and testing to achieve optimal results in providing comfort, support, and injury prevention. Key conclusions include the influence of lattice structures on shoe stiffness and stress distribution, the effectiveness of composite loofah sponge for vibration damping, the benefits of Poron insoles for impact attenuation, the potential injury risk reduction with auxetic shoes, and the need for future research on mechanical tests, parameter investigation, and optimization of shoe sole structures.
Introduction: Carbon plates have been used to increase running shoes’ longitudinal bending stiffness (LBS), but their effect during a long duration run remains unknown. Our study aimed to identify the effect of LBS on energy cost of running (Cr), biomechanics, and fatigue during a half-marathon.
Methods: Thirteen well-trained male runners (half-marathon time < 1 h40) performed two half-marathons at 95% of the running speed associated with their second ventilatory threshold on two separate visits, with either high-LBS shoes (HLBS, with carbon-plates) or standard-LBS (SLBS) shoes. Before and after the half-marathon, Cr at 12 km/h with both shoes (two 6-min bouts: Cr12) and ankle plantarflexors (PF) force were measured. During the half-marathon, running kinematics, shoe perceived comfort, and Cr were assessed.
Results: During Cr12 measurements before and after the half-marathon, HLBS was 1.0 ± 2.1% more economical than SLBS (p < 0.001). During the half-marathon, Cr increased with running duration (p = 0.048) but there was no distance × condition effect. HLBS increased contact time (+3%, p = 0.01), decreased metatarsophalangeal joint dorsiflexion (-9%, p = 0.01), and was perceived less comfortable than SLBS, independently from running duration. At the end of the half-marathon, HLBS shoes led to higher PF force loss (-20.0 ± 9.8% vs -13.3 ± 11.0%, p = 0.048).
Conclusions: Adding curved carbon plates in the running shoes slightly improved Cr during short running bouts at low intensity but not during a half-marathon. This discrepancy may be explained by day-to-day Cr variability and variation in shoe comfort. PF fatigue was higher with HLBS shoes but the accentuated fatigue did not further impact the biomechanical perturbations induced by the plates. Our results suggest that carbon plates alone do not provide a significant advantage for half-marathon performance.
There is debate and confusion over how to evaluate the biomechanical effects of running shoe design. Here we use an evolutionary perspective to analyze how key design features of running shoes alter the evolved biomechanics of the foot, creating a range of tradeoffs in force production and transmission that may affect performance and vulnerability to injury.
Purpose:
Carbon plates have been used to increase running shoes' longitudinal bending stiffness (LBS), leading to reductions in the energy cost of level running (Cr). However, whether or not this is true during uphill (UH) running remains unknown. The aim of our study was to identify the effect of LBS on Cr during UH running.
Methods:
Twenty well-trained male runners participated in this study. Cr was determined using gas exchange during nine 4-minute bouts performed using 3 different LBS shoe conditions at 2.22 and 4.44 m/s on level and 2.22 m/s UH (gradient: + 15%) running. All variables were compared using 2-way analyses of variance (LBS × speed/grade effects).
Results:
There was no significant effect of LBS (F = 2.04; P = .14, ηp2=.11) and no significant LBS × grade interaction (F = 0.31; P = .87, ηp2=.02). Results were characterized by a very large interindividual variability in response to LBS changes.
Conclusions:
The current study contributes to a growing body of literature reporting no effect of LBS on Cr during level and UH running. Yet, the very large interindividual differences in response to changes in LBS suggest that increasing shoe LBS may be beneficial for some runners.
Purpose:
The Nike Vaporfly line of running shoes improves running economy by ∼2.7% to 4.2% at running speeds of 13 to 18 km·h-1. It is unclear whether similar benefits are conferred at slower speeds. Our purpose was to determine the effects of the Nike ZoomX Vaporfly Next% 2 (VFN2) on running economy at 10 and 12 km·h-1 compared with a mass-matched control (CTRL) shoe.
Methods:
Sixteen runners completed 4 × 5-minute trials at both 10 and 12 km·h-1 on the same day. Each shoe was tested twice at each speed in a counterbalanced, mirrored sequence. Data are displayed as mean (SD).
Results:
A 2-way repeated-measures analysis of variance showed a significant shoe × speed interaction for oxygen consumption (P = .021). At 12 km·h-1, oxygen consumption (in mL·kg-1·min-1) was lower (-1.4% [1.1%]; P < .001) for VFN2 (35.8 [1.7]) relative to CTRL (36.4 [1.7]). That was greater in magnitude than the differences observed at 10 km·h-1 (-0.9% [1.8%]; P = .065) between VFN2 (29.4 [1.9]) and CTRL (29.6 [1.9]).
Conclusions:
From these data, it appears that the VFN2 still enhances running economy at 10 and 12 km·h-1; however, these benefits are smaller in magnitude compared with previous research at faster speeds.
Research is often conducted to investigate footwear mechanical properties and their effects on running biomechanics, but little is known about their influence on runner satisfaction, or how well the shoe is perceived. A tool to predict runner satisfaction in a shoe from its mechanical properties would be advantageous for footwear companies. Data in this study were from a database (n = 615 subject-shoe pairings) of satisfaction ratings (gathered after participants ran on a treadmill), and mechanical testing data for 87 unique subjects across 61 unique shoes. Random forest and elastic net logistic regression models were built to test if footwear mechanical properties and subject characteristics could predict runner satisfaction in 3 ways: degree-of-satisfaction on a 7-point Likert scale, overall satisfaction on a 3-point Likert scale, and willingness-to-purchase the shoe (yes/no response). Data were divided into training and validation sets, using an 80–20 split, to build the models and test their accuracy, respectively. Model accuracies were compared against the no-information rate (i.e. proportion of data belonging to the largest class). The models were not able to predict degree-of-satisfaction or overall satisfaction from footwear mechanical properties but could predict runner’s willingness to purchase with 68–75% accuracy. Midsole Gmax at the heel and forefoot appeared in the top five of variable importance rankings across both willingness-to-purchase models, suggesting its role as a major factor in purchase decisions. The negative regression coefficient for both heel and forefoot Gmax indicated that softer midsoles increase the likelihood of a shoe purchase. Future models to predict satisfaction may improve accuracy with the addition of more subject-specific parameters, such as running goals or foot proportions.
The cost of generating force hypothesis proposes that the metabolic rate during running is determined by the rate of muscle force development (1/tc, tc=contact time) and the volume of active leg muscle. A previous study assumed a constant recruited muscle volume and reported that the rate of force development alone explained ∼70% of the increase in metabolic rate for human runners across a moderate velocity range (2-4 m s-1). We hypothesized that over a wider range of velocities, the effective mechanical advantage (EMA) of the lower limb joints would overall decrease, necessitating a greater volume of active muscle recruitment. Ten high-caliber male human runners ran on a force-measuring treadmill at 8, 10, 12, 14, 16 and 18 km hr-1 while we analyzed their expired air to determine metabolic rates. We measured ground reaction forces and joint kinematics to calculate contact time and estimate active muscle volume. From 8 to 18 km hr-1, metabolic rate increased 131% from 9.28 to 21.44 W kg-1 Contact time (tc) decreased from 0.280 sec to 0.190 sec, and thus the rate of force development (1/tc) increased by 48%. Ankle EMA decreased by 19.7±11%, knee EMA increased by 11.1±26.9% and hip EMA decreased by 60.8±11.8%. Estimated active muscle volume per leg increased 52.8% from 1663±152 cm3 to 2550±169 cm3 Overall, 98% of the increase in metabolic rate across the velocity range was explained by just two factors: the rate of generating force and the volume of active leg muscle.
Context
Since decades leg dominance is suggested to be important in rehabilitation and return to play in athletes with anterior cruciate ligament injuries. However, an ideal method to determine leg dominance in relation to task performance is still lacking.
Objective
To test the agreement between self-reported and observed leg dominance in bilateral mobilizing and unilateral stabilizing tasks, and to assess whether the dominant leg switches between bilateral mobilizing tasks and unilateral stabilizing tasks.
Design
Cross-sectional study.
Participants
Forty-one healthy adults: 21 men aged 36 ± 17 years old and 20 women aged 36 ±15 years old.
Measurement and analysis
Participants self-reported leg dominance in the Waterloo Footedness Questionnaire-Revised (WFQ-R), and leg dominance was observed during performance of four bilateral mobilizing tasks and two unilateral stabilizing tasks. Descriptive statistics and crosstabs were used to report the percentages of agreement.
Results
The leg used to kick a ball had 100% agreement between the self-reported and observed dominant leg for both men and women. The dominant leg in kicking a ball and standing on one leg was the same in 66.7% of the men and 85.0% of the women. The agreement with jumping with one leg was lower: 47.6% for men and 70.0% for women.
Conclusions
It is appropriate to ask healthy adults: “If you would shoot a ball on a target, which leg would you use to shoot the ball?” to determine leg dominance in bilateral mobilizing tasks. However, a considerable number of the participants switched the dominant leg in a unilateral stabilizing task.
Background
Quantifying the strength of the intrinsic foot muscles has been a challenge for clinicians and researchers. The reliable measurement of this strength is important in order to assess weakness, which may contribute to a variety of functional issues in the foot and lower leg, including plantar fasciitis and hallux valgus. This study reports 3 novel methods for measuring foot strength – doming (previously unmeasured), hallux flexion, and flexion of the lesser toes.
Methods
Twenty-one healthy volunteers performed the strength tests during two testing sessions which occurred one to five days apart. Each participant performed each series of strength tests (doming, hallux flexion, and lesser toe flexion) four times during the first testing session (twice with each of two raters) and two times during the second testing session (once with each rater). Intra-class correlation coefficients were calculated to test for reliability for the following comparisons: between raters during the same testing session on the same day (inter-rater, intra-day, intra-session), between raters on different days (inter-rater, inter-day, inter-session), between days for the same rater (intra-rater, inter-day, inter-session), and between sessions on the same day by the same rater (intra-rater, intra-day, inter-session).
Results
ICCs showed good to excellent reliability for all tests between days, raters, and sessions. Average doming strength was 99.96 ± 47.04 N. Average hallux flexion strength was 65.66 ± 24.5 N. Average lateral toe flexion was 50.96 ± 22.54 N.
Conclusions
These simple tests using relatively low cost equipment can be used for research or clinical purposes. If repeated testing will be conducted on the same participant, it is suggested that the same researcher or clinician perform the testing each time for optimal reliability.
Background
Reducing the energetic cost of running seems the most feasible path to a sub-2-hour marathon. Footwear mass, cushioning, and bending stiffness each affect the energetic cost of running. Recently, prototype running shoes were developed that combine a new highly compliant and resilient midsole material with a stiff embedded plate. Objective
The aim of this study was to determine if, and to what extent, these newly developed running shoes reduce the energetic cost of running compared with established marathon racing shoes. Methods18 high-caliber athletes ran six 5-min trials (three shoes × two replicates) in prototype shoes (NP), and two established marathon shoes (NS and AB) during three separate sessions: 14, 16, and 18 km/h. We measured submaximal oxygen uptake and carbon dioxide production during minutes 3–5 and averaged energetic cost (W/kg) for the two trials in each shoe model. ResultsCompared with the established racing shoes, the new shoes reduced the energetic cost of running in all 18 subjects tested. Averaged across all three velocities, the energetic cost for running in the NP shoes (16.45 ± 0.89 W/kg; mean ± SD) was 4.16 and 4.01% lower than in the NS and AB shoes, when shoe mass was matched (17.16 ± 0.92 and 17.14 ± 0.97 W/kg, respectively, both p < 0.001). The observed percent changes were independent of running velocity (14–18 km/h). Conclusion
The prototype shoes lowered the energetic cost of running by 4% on average. We predict that with these shoes, top athletes could run substantially faster and achieve the first sub-2-hour marathon.
Purpose:
Our goal was to quantify if small (1 - 3%) changes in running economy quantitatively affect distance-running performance. Based on the linear relationship between metabolic rate and running velocity and on earlier observations that added shoe mass increases metabolic rate by ~1% per 100 grams per shoe, we hypothesized that adding 100 and 300 grams per shoe would slow 3,000m time-trial performance by 1% and 3%, respectively.
Methods:
18 male, sub-20 minute 5km runners completed treadmill testing, and three 3,000m time-trials wearing control shoes and identical shoes with 100 and 300 grams of discreetly added mass. We measured rates of oxygen consumption and carbon dioxide production and calculated metabolic rates for the treadmill tests and we recorded overall running time for the time-trials.
Results:
Adding mass to the shoes significantly increased metabolicrate at 3.5 m·s by 1.11% per 100grams per shoe (95% CI: 0.88-1.35%). While wearing the control shoes, participants ran the 3,000m time-trial in 626.1 ± 55.6s. Times averaged 0.65 ± 1.36% and 2.37 ± 2.09% slower for the +100g and +300g shoes respectively (p<0.001). Based on a linear fit of all the data, 3,000m time increased 0.78% per added 100 grams per shoe (95% CI: 0.52-1.04%).
Conclusion:
Adding shoe mass predictably degrades running economy and slows 3,000m time-trial performance proportionally. Our data demonstrate that laboratory-based running economy measurements can accurately predict changes in distance running race performance due to shoe modifications.
Background:
The effect of footwear on running economy has been investigated in numerous studies. However, no systematic review and meta-analysis has synthesised the available literature and the effect of footwear on running performance is not known.
Objective:
The aim of this systematic review and meta-analysis was to investigate the effect of footwear on running performance and running economy in distance runners, by reviewing controlled trials that compare different footwear conditions or compare footwear with barefoot.
Methods:
The Web of Science, Scopus, MEDLINE, CENTRAL (Cochrane Central Register of Controlled Trials), EMBASE, AMED (Allied and Complementary Medicine), CINAHL and SPORTDiscus databases were searched from inception up until April 2014. Included articles reported on controlled trials that examined the effects of footwear or footwear characteristics (including shoe mass, cushioning, motion control, longitudinal bending stiffness, midsole viscoelasticity, drop height and comfort) on running performance or running economy and were published in a peer-reviewed journal.
Results:
Of the 1,044 records retrieved, 19 studies were included in the systematic review and 14 studies were included in the meta-analysis. No studies were identified that reported effects on running performance. Individual studies reported significant, but trivial, beneficial effects on running economy for comfortable and stiff-soled shoes [standardised mean difference (SMD) <0.12; P < 0.05), a significant small beneficial effect on running economy for cushioned shoes (SMD = 0.37; P < 0.05) and a significant moderate beneficial effect on running economy for training in minimalist shoes (SMD = 0.79; P < 0.05). Meta-analysis found significant small beneficial effects on running economy for light shoes and barefoot compared with heavy shoes (SMD < 0.34; P < 0.01) and for minimalist shoes compared with conventional shoes (SMD = 0.29; P < 0.01). A significant positive association between shoe mass and metabolic cost of running was identified (P < 0.01). Footwear with a combined shoe mass less than 440 g per pair had no detrimental effect on running economy.
Conclusions:
Certain models of footwear and footwear characteristics can improve running economy. Future research in footwear performance should include measures of running performance.
Longitudinal midsole bending stiffness and elasticity are two critical features in the construction of running shoes. Stiff elastic materials (eg, carbon fiber) can be used to alter the midsole bending behavior. The purpose of this study was to investigate the effects of midsole stiffness and elasticity manipulation on metatarsophalangeal (MTP) joint mechanics during running in 19 male subjects at 3.5 m/s. Midsole bending stiffness and elasticity were modified by means of carbon fiber insoles of varying thickness. Stiffening the shoe structures around the MTP joint caused a shift of the point of force application toward the front edge of the shoe-ground interface. Negative work was significantly reduced for the stiffest shoe condition and at the same time a significant increase of positive work at the MTP joint was found. It seems plausible that the increase in positive work originates from the reutilization of elastic energy that was stored inside the passive elastic structures of the shoe and toe flexing muscle tendon units. Further, an increase in midsole longitudinal bending stiffness seems to alter the working conditions and mechanical power generation capacities of the MTP plantar flexing muscle tendon units by changing ground reaction force leverage and MTP angular velocity.
Purpose:
Decreased whole-body energy cost of running has been associated with an increased Achilles tendon stiffness. It is usually assumed that this lower energy cost can be attributed to less muscle fascicle shortening with a stiffer tendon. Increased fiber shortening is an important determinant of muscle energetics in vitro. However, other factors, like increased muscle activation may be important when considering whole muscle energetics in vivo.
Methods:
To determine the effects of a small additional muscle shortening on skeletal muscle energy requirement, 19 subjects performed 30 plantarflexions on two separate occasions: isometric (ISO) and isokinetic (KIN, 6.98 rad s(-1)), each with a target of 50 % of maximum isometric torque. Medial gastrocnemius muscle fascicle length (FL) was measured by ultrasound and rate of oxyhemoglobin (HbO2) desaturation was measured during blood flow occlusion using near-infrared spectroscopy.
Results:
KIN resulted in significantly greater muscle shortening (23.8 ± 1.3 mm) than ISO (18.3 ± 1.0 mm, p < 0.001, mean ± SEM), and greater shortening velocity (KIN = 2.5 ± 0.3 FL s(-1), ISO = 1.1 ± 0.1 FL s(-1), p < 0.001). Rate of HbO2 desaturation was 19 ± 7 %, greater in KIN than ISO (p < 0.01), despite 19 ± 2 % lower mean torque (p < 0.001) and 9.8 ± 1.6 Nm s lower mean impulse per contraction (p < 0.001) in KIN compared to ISO. Root mean square for EMG was significantly greater (p < 0.05) during KIN (73 ± 3 %) than during ISO (63 ± 2 %).
Conclusion:
These results illustrate that muscle energy requirement is greater when muscle fascicle shortening and/or velocity of shortening is increased, and suggest that greater activation contributes to that increased energy requirement.
Recent studies of sprinters and distance runners have suggested that variations in human foot proportions and plantarflexor muscle moment arm correspond to the level of sprint performance or running economy. Less clear, however, is whether differences in muscle moment arm are mediated by altered tendon paths or by variation in the centre of ankle joint rotation. Previous measurements of these differences have relied upon assumed joint centres and measurements of bone geometry made externally, such that they would be affected by the thickness of the overlying soft tissue. Using magnetic resonance imaging, we found that trained sprinters have shorter plantarflexor moment arms (p = 0.011) and longer forefoot bones (p = 0.019) than non-sprinters. The shorter moment arms of sprinters are attributable to differences in the location of the centre of rotation (p < 0.001) rather than to differences in the path of the Achilles tendon. A simple computer model suggests that increasing the ratio of forefoot to rearfoot length permits more plantarflexor muscle work during plantarflexion that occurs at rates expected during the acceleration phase following the sprint start.
The axis of the talo-crural joint was analysed by roentgen stereophotogrammetry in eight healthy volunteers. Examinations were performed at 10 degrees increments of flexion and pronation/supination of the foot as well as medial and lateral rotation of the leg. Results indicate that the talo-crural joint axis changes continuously throughout the range of movement. In dorsiflexion it tended to be oblique downward and laterally. In rotation of the leg, the axis took varying inclinations between horizontal and vertical. All axes in each subject lay close to the midpoint of a line between the tips of the malleoli. Our study indicates that the talo-crural joint axis may alter considerably during the arc of motion and differ significantly between individuals. This prompts caution in the use of hinge axes in orthoses and prostheses for the ankle.
The primary footwear components of interest to improve performance are midsole material, weight, and longitudinal bending stiffness. Little is known about the effects of varied longitudinal bending stiffness across a range of running speeds. The purpose of this study was to identify changes in spatiotemporal variables, horizontal ground reaction forces, subjective comfort, and metabolic cost at different running speeds in response to varied longitudinal bending stiffness. Ten highly trained males ran at 14, 17 and 20 km/h in shoes with varying longitudinal bending stiffness (normal 5.9, stiff 10.5 and very stiff 17.0 N-m/rad). Ground reaction forces, metabolics and subjective comfort assessments were collected. There were significant changes (p < .05) in contact time, stride frequency, and stride length between shoe conditions at all three speeds. Peak propulsive force decreased with increased bending stiffness at all three speeds, but there was no change in braking or propulsive impulse. The patterns of changes in stride length and stride frequency were different between speeds. At 14 km/h, most participants elicited a minimum metabolic rate in the normal shoe. However, at 17 km/h an increased number of participants were more economical in the stiff shoe, despite it weighing an extra 50 g compared to the normal shoe. Running speed had an influence on subjective comfort, with participants tending to prefer the normal shoe at 14 km/h and the stiff shoe at 17 km/h. These results suggest that an optimal bending stiffness to reduce metabolic cost and improve comfort may be running speed dependent.
Altering the longitudinal bending stiffness of footwear has the potential to affect mechanics of the metatarsophalangeal (MTP) joint. Recent efforts have been put forth to identify an optimal bending stiffness of footwear to improve running performance. However, little is known about how this optimal bending stiffness may change with running speed. The purpose of this study was to investigate how dynamic angular stiffness about the MTP joint changes across running speeds. Eighteen participants ran at five speeds from 3.89 to 6.11 m/s. Metatarsophalangeal joint angles, moments, and stiffness were estimated for each speed. Two MTPJ load-displacement metrics were defined, active and critical stiffness. Instantaneous stiffness of the MTP joint was also quantified. There was a significant main effect of speed on critical stiffness (p < .001), max- imum MTP moment (p < .001), MTP moment at maximum dorsiflexion (p < .001), and MTP range of motion (p=.013). There was no effect of speed on active stiffness (p=.094). These results support the notion that involvement of the MTP joint increases with running speed. Individual contributions of the foot and shoe to the MTP joint moment and stiffness suggest that the foot appears to dominate the stiffness of the foot-shoe complex and torque generation about the MTP joint. Instantaneous stiffness fluctuated throughout stance phase, suggesting that foot- shoe complex stiffness is time dependent. The ratio by which critical stiffness and MTP joint range of motion increase with running speed may provide insight for how to guide construction of performance footwear. These results suggest that when utilizing MTP joint mechanics for insights into designing a shoe for performance purposes, the effect of speed should be taken into consideration.
Comfort as an essential parameter for running footwear is gaining importance in footwear research and development, and has also been proposed to decrease injury rate and improve metabolic demand in the paradigm of the comfort filter. The aims of this study were to determine differences in oxygen consumption and biomechanical variables associated with lower extremity injuries in response to running shoes of differing comfort. Fifteen male runners attended two testing sessions including an incremental lactate threshold test, a comfort assessment and treadmill running trials for the biomechanical and physiological measurements. Statistical analyses were performed on oxygen consumption, spatio-temporal variables including foot-ground angle and coupling angle variability of 12 couplings in five stride phases. No decrease in oxygen consumption was found in the most preferred shoe condition. Investigation of potential biomechanical contributors to changes in metabolic demands revealed differences in the stride rate between the most and least preferred condition. In coupling angle variability analyses, only one coupling (ankle dorsiflexion/plantarflexion to knee varus/valgus) yielded a significant difference between conditions in the phase including the touch down. Based on the findings of this study, previous suggestions regarding positive effects of enhanced footwear comfort during running cannot be supported – neither on economy nor on injury prevention perspective. However, a prospective study of lower extremity injury combined with measurements of biomechanical and physiological variables seems to be required for a definite support or contradiction of the comfort filter.
Objectives: To investigate if lower limb joint work is redistributed when running in a shoe with increasedmidsole bending stiffness compared to a control shoe.
Design: Within-subject with two conditions: (1) commercially available running shoe and (2) the sameshoe with carbon fibre inserts to increase midsole bending stiffness.
Methods: Thirteen male, recreational runners ran on an instrumented treadmill at 3.5 m/s in each of thetwo shoe conditions while motion capture and force platform data were collected. Positive and negativemetatarsophalangeal (MTP), ankle, knee, and hip joint work were calculated and statistically comparedbetween conditions.
Results: Running in the stiff condition (with carbon fibre inserts) resulted in significantly more positivework and less negative work at the MTP joint, and less positive work at the knee joint.
Conclusions: Increased midsole bending stiffness resulted in a redistribution of positive lower limb jointwork from the knee to the MTP joint. A larger MTP joint plantarflexor moment due to increased vGRF atthe instant of peak positive power and an earlier onset of MTP joint plantarflexion velocity were identifiedas the reasons for lower limb joint work redistribution.
The choice of marathon racing shoes can greatly affect performance. The purpose of this study is to metabolically and mechanically compare the consumer version of the Nike Vaporfly 4% shoe to two other popular marathon shoes, and determine differences in running economy. Nineteen subjects performed two 5-minute trials at 4.44m/s wearing the Adidas Adios Boost (AB), Nike Zoom Streak (ZS), and Nike Vaporfly 4% (VP) in random order. Oxygen uptake was recorded during minutes 3–5 and averaged across both shoe trials. On a second day, subjects wore reflective markers, and performed a 3-minute trial in each shoe. Motion and force data were collected over the final 30 seconds of each trial. VP oxygen uptake was 2.8% and 1.9% lower than the AB and ZS. Stride length, plantar flexion velocity, and center of mass vertical oscillation were significantly different in the VP. The percent benefit of the VP over AB shoe was predicted by subject ground time. These results indicate that use of the VP shoe results in improved running economy, partially due to differences in running mechanics. Subject variation in running economy improvement is only partially explained by variation in ground time.
The goals of this study were to examine the following hypotheses: (a) there is a difference between the theoretically calculated (McMahon and Cheng, 1990. Journal of Biomechanics 23, 65-78) and the kinematically measured length changes of the spring-mass model and (b) the leg spring stiffness, the ankle spring stiffness and the knee spring stiffness are influenced by running speed. Thirteen athletes took part in this study. Force was measured using a "Kistler" force plate (1000 Hz). Kinematic data were recorded using two high-speed (120 Hz) video cameras. Each athlete completed trials running at five different velocities (approx. 2.5, 3.5, 4.5, 5.5 and 6.5 m/s). Running velocity influences the leg spring stiffness, the effective vertical spring stiffness and the spring stiffness at the knee joint. The spring stiffness at the ankle joint showed no statistical difference (p < 0.05) for the five velocities. The theoretically calculated length change of the spring-mass model significantly (p < 0.05) overestimated the actual length change. For running velocities up to 6.5 m/s the leg spring stiffness is influenced mostly by changes in stiffness at the knee joint.
Purpose: To investigate the joint-specific contributions to the total lower extremity joint work during a prolonged fatiguing run. Methods: Recreational long-distance runners (RR; n = 13) and competitive long-distance runners (CR; n = 12) performed a 10-km treadmill run with near maximal effort. A three-dimensional motion capture system synchronized with a force instrumented treadmill was used to calculate joint kinetics and kinematics of the lower extremity in the sagittal plane during the stance phase at 13 distance points over the 10-km run. Results: A significant (P < 0.05) decrease of positive ankle joint work as well as an increase of positive knee and hip joint work was found. These findings were associated with a redistribution of the individual contributions to total lower extremity work away from the ankle towards the knee and hip joint which was more distinctive in the RR group than in the CR group. This redistribution was accomplished by significant (P < 0.05) reductions of the external ground-reaction force (GRF) lever arm and joint torque at the ankle and by the significant (P < 0.05) increase of the external GRF lever arm and joint torque at the knee and hip. Conclusion: The redistribution of joint work from the ankle to more proximal joints might be a biomechanical mechanism that could partly explain the decreased running economy in a prolonged fatiguing run. This might be
because muscle-tendon units crossing proximal joints are less equipped for energy storage and return compared to ankle plantar flexors and require greater muscle volume activation for a given force. In order to improve running performance, long-distance runners may benefit from an exercise-induced enhancement of ankle plantar flexor muscle-tendon unit capacities.
Changes in running strike pattern affect ankle and knee mechanics, but little is known about the influence of strike pattern on the joints distal to the ankle. The purpose of this study was to explore the effects of forefoot strike (FFS) and rearfoot strike (RFS) running patterns on foot kinematics and kinetics, from the perspectives of the midtarsal locking theory and the windlass mechanism. Per the midtarsal locking theory, we hypothesized that the ankle would be more inverted in early stance when using a FFS, resulting in decreased midtarsal joint excursions and increased dynamic stiffness. Associated with a more engaged windlass mechanism, we hypothesized that a FFS would elicit increased metatarsophalangeal joint excursions and negative work in late stance. Eighteen healthy female runners ran overground with both FFS and RFS patterns. Instrumented motion capture and a validated multi-segment foot model were used to analyze midtarsal and metatarsophalangeal joint kinematics and kinetics. During early stance in FFS the ankle was more inverted, with concurrently decreased midtarsal eversion (p < 0.001) and abduction excursions (p = 0.003) but increased dorsiflexion excursion (p = 0.005). Dynamic midtarsal stiffness did not differ (p = 0.761). During late stance in FFS, metatarsophalangeal extension was increased (p = 0.009), with concurrently increased negative work (p < 0.001). In addition, there was simultaneously increased midtarsal positive work (p < 0.001), suggesting enhanced power transfer in FFS. Clear evidence for the presence of midtarsal locking was not observed in either strike pattern during running. However, the windlass mechanism appeared to be engaged to a greater extent during FFS.
Purpose:
(a) to quantify differences in lower extremity joint kinematics for groups of runners subjected to different running footwear conditions, and (b) to quantify differences in lower extremity joint kinematics on an individual basis for runners subjected to different running footwear conditions.
Methods:
Three-dimensional ankle and knee joint kinematics were collected for 35 heel-toe runners when wearing three different running shoes and when running barefoot. Absolute mean differences in ankle and knee joint kinematics were computed between running shoe conditions. The percentage of individual runners who displayed differences below a 2°, 3° and 5° threshold were also calculated.
Results:
The results indicate that the mean kinematics of the ankle and knee joints were similar between running shoe conditions. Aside from ankle dorsi-flexion and knee flexion, the percentage of runners maintaining their movement path between running shoes (i.e. less than 3°) was in the order of magnitude of about 80 to 100%. Many runners showed ankle and knee joint kinematics that differed between a conventional running shoe and barefoot by more than 3°, especially for ankle dorsiflexion and knee flexion CONCLUSION: Many runners stay in the same movement path (the preferred movement path) when running in various different footwear conditions. The percentage of runners maintaining their preferred movement path depends on the magnitude of the change introduced by the footwear condition.
A local minimum for running energetics has been reported for a specific bending stiffness, implying that shoe stiffness assists in running propulsion. However, the determinant of the metabolic optimum remains unknown. Highly stiff shoes significantly increase the moment arm of the ground reaction force (GRF) and reduce the leverage effect of joint torque at ground push-off. Inspired by previous findings, we hypothesized that the restriction of the natural metatarsophalangeal (MTP) flexion caused by stiffened shoes and the corresponding joint torque changes may reduce the benefit of shoe bending stiffness to running energetics. We proposed the critical stiffness, kcr, which is defined as the ratio of the MTP joint (MTPJ) torque to the maximal MTPJ flexion angle, as a possible threshold of the elastic benefit of shoe stiffness. 19 subjects participated in a running test while wearing insoles with five different bending stiffness levels. Joint angles, GRFs, and metabolic costs were measured and analyzed as functions of the shoe stiffness. No significant changes were found in the take-off velocity of the center of mass (CoM), but the horizontal ground push-offs were significantly reduced at different shoe stiffness levels, indicating that complementary changes in the lower-limb joint torques were introduced to maintain steady running. Slight increases in the ankle, knee, and hip joint angular impulses were observed at stiffness levels exceeding the critical stiffness, whereas the angular impulse at the MTPJ was significantly reduced. These results indicate that the shoe bending stiffness is beneficial to running energetics if it does not disturb the natural MTPJ flexion.
Previous research has shown that altering forefoot (FF) bending stiffness can enhance running economy; however, the mechanism behind the changes in running economy remains unknown. Therefore, the purpose of this study was to investigate the relationship between forefoot bending stiffness, running economy, and lower limb kinematics during overground running. Eighteen aerobically fit recreational male athletes performed overground running using a portable metabolic analysis system to measure oxygen consumption in two footwear conditions with different forefoot bending stiffness. Sagittal plane kinematic data of the metatarsophalangeal, ankle, and knee joints were recorded using a high-speed camera. On average, there was no difference in running economy when running in the Stiff shoe (O2 = 38.1 ± 5.4 mL/kg/min) compared to the Control shoe (O2 = 37.7 ± 5.8 mL/kg/min, p = 0.11). On an individual basis, 10 athletes (Responders) improved their running economy with increased FF bending stiffness (∆O2 = −2.9%), while eight athletes (Non-Responders) worsened or did not improve their running economy in a stiff shoe (∆O2 = +1.0%). In stiff footwear, Responders experienced kinematic changes at the ankle joint (decreased angular velocity) that likely resulted in decreased energy requirement for muscular contractions due to a presumed shift on their individual force–velocity relationship. The lack of improvement in running economy by the Non-Responders may be attributed to a presumed lack of a shift in the force–velocity relationship of the calf musculature. Instead, Non-Responders experienced kinematic changes (increased ankle plantarflexion during push phase with stiff footwear) that likely hindered their moment-generating capability potentially due to a shift on their individual force–length relationship. These findings represent important progress towards explaining inter-individual changes in running economy with different footwear bending stiffness.
The purpose of the present study was to test for differences in ankle palantarflexion strengths of habitually rearfoot and forefoot runners. In order to approach this issue, we revisit the problem of classifying different footfall patterns in human runners. A dataset of 119 subjects running shod and barefoot (speed 3.5 m/s) was analyzed. The footfall patterns were clustered by a novel statistical approach, which is motivated by advances in the statistical literature on functional data analysis. We explain the novel statistical approach in detail and compare it to the classically used strike index of Cavanagh and Lafortune (1980).
The two groups found by the new cluster approach are well interpretable as a forefoot and a rearfoot footfall groups. The subsequent comparison study of the clustered subjects reveals that runners with a forefoot footfall pattern are capable of producing significantly higher joint moments in a maximum voluntary contraction (MVC) of their ankle plantarflexor muscles tendon units; difference in means: 0.28 Nm/kg. This effect remains significant after controlling for an additional gender effect and for differences in training levels.
Our analysis confirms the hypothesis that forefoot runners have a higher mean MVC plan-tarflexion strength than rearfoot runners. Furthermore, we demonstrate that our proposed stochas-tic cluster analysis provides a robust and useful framework for clustering foot strikes.
Footwear comfort has been shown to have an influence on injuries, but it was unknown whether comfort was related to performance. The current study examined the effects of footwear comfort on running economy. Thirteen male participants rated five pairs of shoes on perceived comfort. Oxygen consumption was assessed during steady state runs in the least and most comfortable shoes at slightly above the aerobic threshold. A paired t-test was used to compare running economy in the most versus the least comfortable shoe conditions. The findings of the study indicated a significant improvement in running economy, 0.7% on average, in the most comfortable shoe condition. It is suggested that future study of kinematic and kinetic reactions to footwear of different comfort will help to understand the mechanism for the observed performance improvement.
Running economy is a key determinant of endurance performance, and understanding the biomechanical factors that affect it is of great theoretical and applied interest. This study aimed to analyse how the ground-contact time and strike pattern used by competitive runners concurrently affect running economy.
Cross-sectional.
Fourteen sub-elite male competitive distance runners completed a 6-min submaximal running trial at 14kmh(-1) on an outdoor track using their habitual strike pattern (n=7 rearfoot strikers: average age, 25.3 years old (SD=2.4); average weight, 64.7kg (SD=5.6); average height, 175.3cm (SD=5.2); n=7 midfoot strikers: average age, 25.0 years old (SD=2.8); average weight, 69.6kg (SD=4.0); average height, 180.1cm (SD=5.1). During the run, the oxygen uptake and ground-contact time were measured.
Midfoot strikers showed a significantly shorter (p=0.015) mean contact time (0.228s (SD=0.009)) compared with rearfoot strikers (0.242s (SD=0.010)). Conversely, there was no significant difference (p>0.05) between the groups with respect to mean oxygen uptake (midfoot strikers: 48.4mlmin(-1)kg(-1) (SD=5.3); rearfoot strikers: 49.8mlmin(-1)kg(-1) (SD=6.4)). Linear modelling analysis showed that the effect of contact time on running economy was very similar in the two groups, with a 1ms longer contact time involving an approximately 0.51mlmin(-1)kg(-1) lower oxygen uptake. In contrast, when controlling for contact time, midfoot striking involved an approximately 8.7mlmin(-1)kg(-1) lower oxygen uptake compared with rearfoot striking.
When adjusting the foot-ground contact biomechanics of a runner with the aim of maximising running economy, a trade-off between a midfoot strike and a long contact time must be pursued.
The purposes of this investigation were to determine if increasing the bending stiffness of sprint shoes increases sprinting performance and to determine whether simple anthropometric factors can be used to predict shoe bending stiffness for optimal performance. Thirty-four athletes were tested using four different shoe conditions--a standard condition consisting of their currently used footwear and three conditions where the bending stiffness was increased systematically. The sprinters performed maximal effort 40 m sprints and their sprint times were recorded from 20 to 40 m. On average, increasing the shoe bending stiffness increased sprint performance. The stiffness each athlete required for his or her maximal performance was subject specific but was not related to subject mass, height, shoe size or skill level. It is speculated that individual differences in the force-length and force-velocity relationships of the calf muscles may influence the appropriate shoe stiffness for each athlete to obtain their maximal performance.
The maximal force a muscle produces depends among others on the length of the muscle and therefore on the positions of the joints the muscle crosses. Long and short toe flexor muscles (TFM) cross the ankle joints and metatarsal phalangeal joints (MPJ) and work against gravity during human locomotion. The purpose of this study was to describe the maximal moments around the MPJ during maximal voluntary isometric contractions (MVIC) of the TFM as a function of ankle joint and MPJ position. Twenty men performed MVIC of the TFM in a custom-made dynamometer. Ankle and MPJ angles were modified after each contraction. External moments of force around the MPJ were determined. Moments ranged between 6.3 ± 2.6 Nm and 14.2 ± 5.8 Nm. Highest moments were produced at 0°-10° ankle joint dorsal flexion and 25°-45° MPJ dorsal flexion. Lowest moments were generated at 35° ankle joint plantar flexion and 0° MPJ dorsal flexion. In conclusion, if the ankle is plantar-flexed, dorsal flexion of the MPJ avoids a disadvantage of the force-length relationship of TFM. Therefore, MPJ dorsal flexion is a necessary function in the push-off phase of human locomotion to work against the loss of the mechanical output at the forefoot caused by plantar flexion of the ankle.
Bipedal walking models with compliant legs have been employed to represent the ground reaction forces (GRFs) observed in human subjects. Quantification of the leg stiffness at varying gait speeds, therefore, would improve our understanding of the contributions of spring-like leg behavior to gait dynamics. In this study, we tuned a model of bipedal walking with damped compliant legs to match human GRFs at different gait speeds. Eight subjects walked at four different gait speeds, ranging from their self-selected speed to their maximum speed, in a random order. To examine the correlation between leg stiffness and the oscillatory behavior of the center of mass (CoM) during the single support phase, the damped natural frequency of the single compliant leg was compared with the duration of the single support phase. We observed that leg stiffness increased with speed and that the damping ratio was low and increased slightly with speed. The duration of the single support phase correlated well with the oscillation period of the damped complaint walking model, suggesting that CoM oscillations during single support may take advantage of resonance characteristics of the spring-like leg. The theoretical leg stiffness that maximizes the elastic energy stored in the compliant leg at the end of the single support phase is approximated by the empirical leg stiffness used to match model GRFs to human GRFs. This result implies that the CoM momentum change during the double support phase requires maximum forward propulsion and that an increase in leg stiffness with speed would beneficially increase the propulsion energy. Our results suggest that humans emulate, and may benefit from, spring-like leg mechanics.
Better running economy (i.e. a lower rate of energy consumption at a given speed) is correlated with superior distance running performance. There is substantial variation in running economy, even among elite runners. This variation might be due to variation in the storage and reutilization of elastic energy in tendons. Using a simple musculoskeletal model, it was predicted that the amount of energy stored in a tendon during a given movement depends more critically on moment arm than on mechanical properties of the tendon, with the amount of stored energy increasing as the moment arm gets smaller. Assuming a link between elastic energy reutilization and overall metabolic cost of running, a smaller moment arm should therefore be associated with superior running economy. This prediction was confirmed experimentally in a group of 15 highly trained runners. The moment arm of the Achilles tendon was determined from standardized photographs of the ankle, using the position of anatomical landmarks. Running economy was measured as the rate of metabolic energy consumption during level treadmill running at a speed of 16 km h(-1). A strong correlation was found between the moment arm of the Achilles tendon and running economy. Smaller muscle moment arms correlated with lower rates of metabolic energy consumption (r(2)=0.75, P<0.001).
Twenty female and 45 male middle and long-distance runners, in training for the U.S. Olympic Trials, served as subjects. Ninety percent of both men and women subjects reached the Trials; eight women and 12 men qualified for the Olympic Games and five won medals. Each subject completed a VO2max and a series of submax treadmill runs, for the purpose of comparing heart rate (HR), VO2, and blood lactate (HLa) among men and women and among runners of various event specialties. Results showed the men to be taller, heavier, to have a lower six-site skinfold sum and a higher VO2max, than the women (P less than 0.05); there was no difference in age. When compared in running economy, men used less oxygen (ml.min-1.kg-1) at common absolute velocities, but VO2 (ml.km-1.kg-1) was not different between men and women at equal relative intensities (%VO2max). When men and women of equal VO2max were compared, the men were significantly more economical, using any method of comparison. Also, when comparisons of men and women of equal economy were made, it was found that the men had an even greater advantage over the "matched" women subjects than the mean VO2max comparison using all subjects. In looking at the SD (800-/1500-m runners), MD (3-K/5-K/10-K runners) and LD (marathon runners), it was found that the SD runners used the least oxygen (ml.min-1.kg-1) at speeds of marathon race pace and faster, but not at slower speeds. Men and women responded similarly in this regard. Running economy data for speeds slower than typical race paces, tended to show the LD runners to be most economical, suggesting that the speeds over which runners are tested plays an important part in determining which subjects are the most economical. It was concluded that at absolute running velocities, men are more economical than women, but when expressed in ml.km-1.kg-1 there are no gender differences at similar relative intensities of running. Also, when men and women of equal VO2max or equal economy are matched, the men show a better aerobic profile. It is recommended that economy data be collected up to speeds equal to over 90% VO2max.
When humans and other mammals run, the body's complex system of muscle, tendon and ligament springs behaves like a single linear spring ('leg spring'). A simple spring-mass model, consisting of a single linear leg spring and a mass equivalent to the animal's mass, has been shown to describe the mechanics of running remarkably well. Force platform measurements from running animals, including humans, have shown that the stiffness of the leg spring remains nearly the same at all speeds and that the spring-mass system is adjusted for higher speeds by increasing the angle swept by the leg spring. The goal of the present study is to determine the relative importance of changes to the leg spring stiffness and the angle swept by the leg spring when humans alter their stride frequency at a given running speed. Human subjects ran on treadmill-mounted force platform at 2.5ms-1 while using a range of stride frequencies from 26% below to 36% above the preferred stride frequency. Force platform measurements revealed that the stiffness of the leg spring increased by 2.3-fold from 7.0 to 16.3 kNm-1 between the lowest and highest stride frequencies. The angle swept by the leg spring decreased at higher stride frequencies, partially offsetting the effect of the increased leg spring stiffness on the mechanical behavior of the spring-mass system. We conclude that the most important adjustment to the body's spring system to accommodate higher stride frequencies is that leg spring becomes stiffer.
Human runners adjust the stiffness of their stance leg to accommodate surface stiffness during steady state running. This adjustment allows runners to maintain similar center of mass movement (e.g., ground contact time and stride frequency) regardless of surface stiffness. When runners encounter abrupt transitions in the running surface, they must either make a rapid adjustment or allow the change in the surface stiffness to disrupt their running mechanics. Our goal was to determine how quickly runners adjust leg stiffness when they encounter an abrupt but expected change in surface stiffness that they have encountered previously. Six human subjects ran at 3 m s(-1) on a rubber track with two types of rubber surfaces: a compliant "soft" surface (ksurf = 21.3 kN m(-1) and a non-compliant "hard" surface (ksurf = 533 kN m(-1). We found that runners completely adjusted leg stiffness for their first step on the new surface after the transition. For example, runners decreased leg stiffness by 29% between the last step on the soft surface and the first step on the hard surface (from 10.7 kN m(-1) to 7.6 kN m(-1), respectively). As a result, the vertical displacement of the center of mass during stance ( approximately 7 cm) did not change at the transition despite a reduction in surface compression from 6 cm to less than 0.25 cm. By rapidly adjusting leg stiffness, each runner made a smooth transition between surfaces so that the path of the center of mass was unaffected by the change in surface stiffness.
A substantial amount of rotational energy is lost at the metatarsophalangeal joint during running and jumping. We hypothesized that the lost energy could be decreased by increasing the bending stiffness of shoe midsoles. The purposes of this investigation were to determine the influence of stiff shoe midsoles on changes in lower extremity joint power during running and jumping and to determine the influence of stiff shoe midsoles on vertical jump performance.
Carbon fiber plates were inserted into shoe midsoles and data were collected on five subjects during running and vertical jumping.
The data showed that energy generation and absorption at each of the ankle, knee, and hip joints was not influenced by the stiffness of the shoe midsole. The stiff shoes with the carbon fiber plates did not increase the amount of energy stored and reused at the metatarsophalangeal joint; however, they reduced the amount of energy lost at this joint during both running and jumping. Vertical jump height was significantly higher (average, 1.7 cm for a group of 25 subjects) while wearing the stiff shoes.
Increasing the bending stiffness of the metatarsophalangeal joint reduced the amount of energy lost at that joint and resulted in a corresponding improvement of performance.
OBJECTIVE: To obtain descriptive information between vertical ground reaction force (GRF)-time histories and gait speed, running style, and gender. DESIGN: GRF-time history measurements were obtained from male and female subjects during walking, slow jogging, jogging and running on an indoor platform. BACKGROUND: Previous studies have established GRF descriptor variables for male subjects running at speeds from 3 to 6 m s(-1), but very little descriptive data exists for slower or faster running, nor have previous studies reported GRF descriptors separately for female subjects. METHODS: GRF-time histories were recorded for 13 male and 10 female recreational athletes during walking and slow jogging at speeds between 1.5 and 3.0 m s(-1), and running at speeds between 3.5 and 6.0 m s(-1). Vertical GRF-time data for trials with speeds within 0.2 m s(-1) of the prescribed speed were analysed to determine thrust maximum GRF (F(z)) and loading rate (G(z)). RESULTS: In both male and female subjects, F(z) increased linearly during walking and running from 1.2 BW to approximately 2.5 BW at 6.0 m s(-1), remaining constant during forward lean sprinting at higher speeds. F(z) was linearly correlated to G(z), the latter ranging from 8 to 30 BW s(-1) over this speed range. Slow jogging was associated with a > 50% higher F(z) and G(z) in comparison to walking or fast running. CONCLUSIONS: Similar GRF descriptor data and velocity relationships were obtained for male and female subjects. Impact forces were greatest when the subjects adopted a higher, less fixed centre of gravity during slow jogging. RELEVANCE: These results suggest that vertical GRF norms can be established for male and female subjects alike, and that slow or fast running with a lower, fixed centre of gravity decreases impact forces.
The present study was designed to investigate kinematics, kinetics, and muscle activity for explaining running economy at different running speeds.
A total of 17 young endurance runners ran at 12-13 different running speeds. Respiratory gases were collected. Kinematic records were obtained by a high-speed video camera, and 3-D ground reaction forces (GRF) were measured simultaneously with telemetric EMG recordings of the selected leg muscles. In the analysis, joint moments and power were calculated by inverse dynamic methods.
The oxygen consumption and energy expenditure increased quite linearly with increasing running speed. However, already at the slowest speed, interindividual differences in running economy were noticed, and they increased with increasing running speed. Simultaneously, the instantaneous joint moment-angular velocity curves of the ankle and knee joints shifted to the right and upward, thus increasing joint power in the push-off phase of contact. Most definitive was the increase in EMG-activity of the BF muscle and its correlation with energy expenditure (r = 0.48, P < 0.05). This two-joint muscle seems to be very active during the maximal running: its amplitude increased (P < 0.05) both in the swinging and contact phases with increasing running speed.
The increased EMG of working muscles and the associated increase in power output may partly explain the increased energy expenditure with increasing running speed. Lower performances in running economy by some of the athletes may also be explained by poor running technique, such as unusually high braking and mediolateral forces, which may be caused by limited action of the hamstring muscles. However, no exclusive biomechanical parameters could be identified to explain the running economy.
The purposes of this investigation were to determine if increasing the bending stiffness of sprint shoes increases sprinting performance and to determine whether simple anthropometric factors can be used to predict shoe bending stiffness for optimal performance. Thirty-four athletes were tested using four different shoe conditions--a standard condition consisting of their currently used footwear and three conditions where the bending stiffness was increased systematically. The sprinters performed maximal effort 40 m sprints and their sprint times were recorded from 20 to 40 m. On average, increasing the shoe bending stiffness increased sprint performance. The stiffness each athlete required for his or her maximal performance was subject specific but was not related to subject mass, height, shoe size or skill level. It is speculated that individual differences in the force-length and force-velocity relationships of the calf muscles may influence the appropriate shoe stiffness for each athlete to obtain their maximal performance.
Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally, high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types. Differences in lower extremity kinetics in individuals with different foot types may have implications for new treatment strategies or preventative measures.
This study characterizes the stiffness of the human forefoot during running. The forefoot stiffness, defined as the ratio of ground reaction moment to angular deflection of the metatarsophalangeal joint, is measured for subjects running barefoot. The joint deflection is obtained from video data, while the ground reaction moment is obtained from force plate and video data. The experiments show that during push-off, the forefoot stiffness rises sharply and then decreases steadily, showing that the forefoot behaves not as a simple spring, but rather as an active mechanism that exhibits a highly time-dependent stiffness. The forefoot stiffness is compared with the bending stiffness of running shoes. For each of four shoes tested, the shoe stiffness is relatively constant and generally much lower than the mean human forefoot stiffness. Since forefoot stiffness and shoe bending stiffness act in parallel (i.e., are additive), the total forefoot stiffness of the shod foot is dominated by that of the human foot.
It has been shown that mechanical energy is dissipated at the metatarsophalangeal (MTP) joint during running and jumping. Furthermore, increasing the longitudinal bending stiffness of the midsole significantly reduced the energy dissipated at the MTP joint and increased jump performance. It was hypothesized that increasing midsole longitudinal bending stiffness would also lead to improvements in running economy. This study investigated the influence of midsole longitudinal bending stiffness on running economy (performance variable) and evaluated the local effects on joint energetics and muscular activity.
Carbon fiber plates were inserted into running shoe midsoles and running economy, joint energy, and electromyographic (EMG) data were collected on 13 subjects.
Approximately a 1% metabolic energy savings was observed when subjects ran in a stiff midsole relative to the control midsole. Subjects with a greater body mass had a greater decrease in oxygen consumption rates in the stiff midsole relative to the control midsole condition. The stiffer midsoles showed no significant differences in energy absorption at the MTP joint compared with the control shoe. Finally, no significant changes were observed in muscular activation.
Increasing midsole longitudinal bending stiffness led to improvements in running economy, yet the underlying mechanisms that can be attributed to this improvement are still not fully understood.
The purposes of this study were 1) to determine the intrarater and interrater reliability of the arch height index measurement system device, 2) to establish population normative values for the arch height index in recreational runners, and 3) to compare arch height index values between the right and left feet and between genders.
Eleven subjects were used to establish intrarater and interrater reliability of the arch height index measurement system. This system was then used to measure the arch height index of 100 recreational runners.
Measurements taken with the arch height index measurement system device exhibited high intrarater and interrater reliability. The mean +/- SD arch height index of the recreational runners was 0.340 +/- 0.030. Men had larger feet than women, but the arch height index between genders was similar.
The arch height index measurement system device is reliable to use between testers while simplifying the measurement procedure for recording the arch height index. The arch height index may be helpful in identifying potential structural factors that predispose individuals to lower-extremity injuries.
The gearing function of running shoe longitudinal bending stiffness
- S Willwacher
- M König
- B Braunstein
- J.-P Goldmann
- G.-P Brüggemann