Running Style Research Articles

Heel strike angle and foot angular velocity in the sagittal plane during running in different shoe conditions

Runners change their running style, e.g. heel strike strategy, to adapt to different shoe conditions [1]. Various mechanisms for adaptation are discussed [2,3]. Alteration of stiffness of the ankle joint at heel strike by dorsiflexion or plantarflexion of the foot seems to be disregarded as mechanism of adaptation. In this study, alterations of heel strike angle (HSA) and plantarflexion velocity (PFV) in the sagittal plane due to wearing different shoe conditions was examined. By this, adaptation in running style as a mechanism of shock attenuation should be investigated.

Vermehrte Inzidenz von Plantarfasziosen bei Vorfußläufern

Summary More and runners change their running style to forefoot running in order to become faster, run more actively or to prevent typical running injuries. Hence, the aim of the present study was to investigate whether forefoot and rearfoot runners show different injury patterns regarding location and frequency distribution. For this purpose 612 runners who's running pattern was analyzed biomechanically and who were treated at our facility due to various typical running injuries were evaluated retrospectively. 146 out of the 612 patients were forefoot runners, 466 patients were midfoot and forefoot runners. The forefoot runner percentage of the total sample was therefore 23.9% which corresponds approximately to the percentage within a healthy running population. The percentages of forefoot runners within the most of the typical injury groups were also in the same order of magnitude and showed no significant differences (Achilles tendon: 21%, Toe flexors and M. tibialis posterior: 25.7%, pelvis/spine: 25.6%, thigh: 27.8%). Remarkable is, that in contrast to other studies the Achilles tendon injury group showed no increased quota for the forefoot runners. In the group of knee injuries, however, the forefoot runners were represented ony by 19.1%, which indicates that the probability to injure the knee using the forefoot running style is reduced. Within the group of plantar fasciosis the forefoot runners were represented by 34.2%, which is than 30% higher compared to the total sample. Hence, it can be concluded that forefoot runners have a higher risk to injure their plantar fascia than rearfoot runners.

Knee Angular Impulse as a Predictor of Patellofemoral Pain in Runners

Background Identification of mechanical factors associated with patellofemoral pain, the most prevalent running injury, is necessary to help in injury prevention, but unfortunately they remain elusive. Hypothesis Runners who develop patellofemoral pain have increased knee joint angular impulse in the frontal plane. Study Design Case control study; Level of evidence, 3. Methods A retrospective study compared knee abduction impulses of 20 patellofemoral pain patients with those of 20 asymptomatic patients. A second prospective study quantified knee angular impulses during the stance phase of running of 80 runners at the beginning of the summer running season. Epidemiologic data were then collected, recording the type and severity of injury of these runners during a 6-month running period. Results The patellofemoral pain patients in the retrospective study had significantly higher (P =. 026) knee abduction impulses (17.0 ± 8.5 Nms) than did the asymptomatic patients (12.5 ± 5.5 Nms). Six patients developed patellofemoral pain during the prospective study. The prospective data showed that patients who developed patellofemoral pain had significantly higher (P =. 042) knee abduction impulses (9.2 ± 3.7 Nms) than did matched patients who remained uninjured (4.7 ± 3.5 Nms). Conclusion The data indicate that increased knee abduction impulses should be deemed risk factors that play a role in the development of patellofemoral pain in runners. Clinical Relevance Footwear and running style can influence knee angular impulse, and the appropriate manipulation of these variables may play a preventive role for patients who are predisposed to patellofemoral pain.

A Lower-Extremities Kinematic Comparison of Deep-Water Running Styles and Treadmill Running

The purpose of this investigation was to identify a deep-water running (DWR) style that most closely approximates terrestrial running, particularly relative to the lower extremities. Twenty intercollegiate distance runners (women, N = 12; men, N = 8) were videotaped from the right sagittal view while running on a treadmill (TR) and in deep water at 55-60% of their TR VO(2)max using 2 DWR styles: cross-country (CC) and high-knee (HK). Variables of interest were horizontal (X) and vertical (Y) displacement of the knee and ankle, stride rate (SR), VO(2), heart rate (HR), and rating of perceived exertion (RPE). Multivariate omnibus tests revealed statistically significant differences for RPE (p < 0.001). The post hoc pairwise comparisons revealed significant differences between TR and both DWR styles (p < 0.001). The kinematic variables multivariate omnibus tests were found to be statistically significant (p < 0.001 to p < 0.019). The post hoc pairwise comparisons revealed significant differences in SR (p < 0.001) between TR (1.25 +/- 0.08 Hz) and both DWR styles and also between the CC (0.81 +/- 0.08 Hz) and HK (1.14 +/- 0.10 Hz) styles of DWR. The CC style of DWR was found to be similar to TR with respect to linear ankle displacement, whereas the HK style was significantly different from TR in all comparisons made for ankle and knee displacement. The CC style of DWR is recommended as an adjunct to distance running training if the goal is to mimic the specificity of the ankle linear horizontal displacement of land-based running, but the SR will be slower at a comparable percentage of VO(2)max.

Shock Absorption During Forefoot Running and its Relationship to Medial Longitudinal Arch Height

Overuse injuries to the lower extremity have often been connected with the repetitive loading of the foot and in particular its ability to absorb shock. The shock absorbing ability of the foot is thought to relate to its structure, particularly the height of the medial longitudinal arch. The purpose of this study was to investigate the shock absorption characteristics of the foot in forefoot running as measured by the dynamic load rate of the vertical ground reaction forces during the early stages of ground contact and to relate these characteristics to the height of the medial longitudinal arch. Eighteen normal athletic adult volunteers were used as subjects and all had clinically normal feet. An Arch Index was computed from lateral radiographs taken with the foot in a full weightbearing position. Dynamic load rate was computed as the first differential of the vertical force as measured by a Kistler force platform. Each subject performed ten trials of running at a speed of 3 m.s-1 using forefoot running style. The dynamic load rate showed three definite peaks (mean 93, 18, and 16 kNs-1 respectively), and two intervening troughs (mean 18 and 3 kNs-1 respectively), showing that the process of shock absorption was one that was progressive over the foot loading phase. The time at which these features occurred indicated a consistency in process of shock absorption. However, none of the force peaks or load rate peaks correlated with the Arch Index. It was concluded that the structure of the foot as characterized by the Arch Index, was not the major factor in determining the way in which force is transmitted to the musculoskeletal system in forefoot running. These findings support the concept that the height of the arch, although a commonly used clinical descriptor of foot type does not appear to be important in defining the functional capacity of the foot in action.

Effects of Size, Sex, and Voluntary Running Speeds on Costs of Locomotion in Lines of Laboratory Mice Selectively Bred for High Wheel‐Running Activity

Selective breeding for over 35 generations has led to four replicate (S) lines of laboratory house mice (Mus domesticus) that run voluntarily on wheels about 170% more than four random-bred control (C) lines. We tested whether S lines have evolved higher running performance by increasing running economy (i.e., decreasing energy spent per unit of distance) as a correlated response to selection, using a recently developed method that allows for nearly continuous measurements of oxygen consumption (VO2) and running speed in freely behaving animals. We estimated slope (incremental cost of transport [COT]) and intercept for regressions of power (the dependent variable, VO2/min) on speed for 49 males and 47 females, as well as their maximum VO2 and speeds during wheel running, under conditions mimicking those that these lines face during the selection protocol. For comparison, we also measured COT and maximum aerobic capacity (VO2max) during forced exercise on a motorized treadmill. As in previous studies, the increased wheel running of S lines was mainly attributable to increased average speed, with males also showing a tendency for increased time spent running. On a whole-animal basis, combined analysis of males and females indicated that COT during voluntary wheel running was significantly lower in the S lines (one-tailed P=0.015). However, mice from S lines are significantly smaller and attain higher maximum speeds on the wheels; with either body mass or maximum speed (or both) entered as a covariate, the statistical significance of the difference in COT is lost (one-tailed P> or =0.2). Thus, both body size and behavior are key components of the reduction in COT. Several statistically significant sex differences were observed, including lower COT and higher resting metabolic rate in females. In addition, maximum voluntary running speeds were negatively correlated with COT in females but not in males. Moreover, males (but not females) from the S lines exhibited significantly higher treadmill VO2max as compared to those from C lines. The sex-specific responses to selection may in part be consequences of sex differences in body mass and running style. Our results highlight how differences in size and running speed can account for lower COT in S lines and suggest that lower COT may have coadapted in response to selection for higher running distances in these lines.

Kinetic Changes with Fatigue and Relationship to Injury in Female Runners

This research examined how ground reaction forces (GRF) changed with fatigue induced by an exhaustive treadmill run in female runners. A separate retrospective and prospective analysis correlated initial magnitude of GRF and fatigue-induced changes in GRF with lower-extremity injury. Ninety adult female runners had vertical GRF measured before and after an exhaustive treadmill run. Subjects initially were questioned about previous running injuries, and were contacted during the following year and asked to report any additional running injuries. Fatigue induced by the exhaustive treadmill run resulted in decreased impact peak and loading rates in all runners by an average of 6 and 11%, respectively. The changes in GRF were attributed to altered running cadence, step length, and lower-extremity joint kinematics. It is unclear whether these changes were attempts by the runners to minimize impact forces and protect against injury, or represented a fatigue-induced loss of optimal performance capabilities. An interaction between injury in the previous year and change in impact loading rate with fatigue was observed, suggesting previously injured runners are exposed to relatively higher impact forces over time. Habitual female runners appear to adapt their running style with fatigue, resulting in altered GRF. Changes in GRF with fatigue may be associated with lower-extremity running injuries.

Reduced Eccentric Loading of the Knee with the Pose Running Method

The aim of this study was to compare the biomechanical changes during natural heel-toe running with learned midfoot and Pose running. Twenty heel-toe runners were instructed in midfoot running and a novel running style in which the acromium, greater trochanter, and lateral malleolus are aligned in stance (Pose running). Clinical gait analysis was performed for each running style and the biomechanical variables compared. In comparison with midfoot and heel-toe running Pose running was characterized by shorter stride lengths and smaller vertical oscillations of the sacrum and left heel marker. Compared with midfoot and Pose running heel-toe running was characterized by greater magnitudes and loading rates of the vertical impact force. In preparation for initial contact, the knee flexed more in Pose than in heel-toe and midfoot running. The ankle at initial contact was neutral in Pose compared with a dorsiflexed and plantarflexed position in heel-toe and midfoot running, respectively. The knee power absorption and eccentric work were significant lower (P < 0.05) in Pose than in either heel-toe or midfoot running. In contrast, there was a higher power absorption and eccentric work at the ankle in Pose compared with heel-toe and midfoot running. Pose running was associated with shorter stride lengths, smaller vertical oscillations of the sacrum and left heel markers, a neutral ankle joint at initial contact, and lower eccentric work and power absorption at the knee than occurred in either midfoot or heel-toe running. The possibility that such gait differences could be associated with different types and frequencies of running injuries should be evaluated in controlled clinical trails.

The Relationships Between Local Muscular Endurance and Kinematic Changes During a Run to Exhaustion at v&amp;Vdot;o2max

The relationships between local muscular endurance and kinematic changes during a run to exhaustion at vVo2max. J Strength Cond. Res. 18(4):000-000. 2004.-A recent study suggested that runners who maintain a stable running style are able to run for longer at vVo2max velocity (vVo2max). This may be because of the capacity of various muscle groups to maintain their functions despite the onset of fatigue. The purpose of this study was to examine the relationship between local muscular endurance of both the hip and knee extensor and flexor muscle groups and the kinematic changes during a run to exhaustion at vVo2max. Six subelite runners (age 24.2 + 4.2) participated in this study;they were considered as a homogeneous group based upon theirvVo2max scores (coefficient of variation = 3.9%). They performed an incremental protocol to determine vVo2max, a series of isokinetic tests to determine the local muscular endurance of both knee and hip flexors and extensors, and a run to exhaustion at vVo2max. The change in kinematic variables between the beginning and the end of the run were correlated with the measures of muscular endurance. Several statistically significant negative correlations emerged between the change in stride length and concentric hip extension (HE(con)), r = -0.934; eccentric hip extension (HE(ecc)), r = -0.818; eccentric knee flexion(KF(ecc)), r = -0.957; and change in maximum hip extension (Delta max HE), r - -0.857; and Delta max HE with HE(con), r = -0.846.We concluded that the local muscular endurance of both HE(con) and KF(ecc) are important in maintaining a stable running style.

Isaiah 56-66: A New Translation with Introduction and Commentary (review)

Hebrew Studies 45 (2004) 328 Reviews public relief program that guaranteed their material endowment (pp. 171– 172). However, in the Hebrew Bible, the Omrides and more particularly Ahab do not stand out as YHWH-alone champions but are always associated with Baal and Ashera. In other words, the textual data (e.g., 1 Kgs 16:29– 17:1; 18; 19; etc.) do not appear to mesh with this reconstruction. Bennett includes a final brief concluding chapter 6 (pp. 173–176) which is followed by a bibliography (pp. 177–200) and three indices (pp. 201–209) involving authors, subjects, and Scripture references. While his concern for the oppressed is laudable and important, his methodological presuppositions debilitate the results. At the end, one is left with one simple decision: either to accept Bennett’s application of critical law theory, that is, law as a tool in the hand of some groups to manipulate, empower, or marginalize social subgroups , or to reject it. While it may not be fashionable, I would rather favor a more thorough dialogue with the primary data (i.e., the biblical text) instead of beginning with a closed model that will then be used as a filter to read that primary data. After reading Bennett’s work, which is so heavily indebted to social science research and methodology, one wonders what happened to the theological dimension of the biblical texts. Should it not be possible that ethics , theology, and social sciences try to meet on more equal grounds when deciphering the biblical text? Gerald A. Klingbeil River Plate Adventist University Libertador San Martin, Argentina kling@uap.edu.ar ISAIAH 56–66: A NEW TRANSLATION WITH INTRODUCTION AND COMMENTARY. By Joseph Blenkinsopp. AB. Pp. xvi + 348. New York: Doubleday, 2003. Cloth, $45.00. This is the third and final volume of Blenkinsopp’s commentary on Isaiah. Along with the recent works of J. D. W. Watts (Isaiah 1–33 and Isaiah 34–66 [WBC 24 and 25; Waco, Tex.: Word Books, 1985 and 1987]), J. M. Oswalt (The Book of Isaiah: Chapters 1–39 and Chapters 40–66 [NICOT; Grand Rapids, Mich.: Eerdmans, 1986 and 1998]) and B. S. Childs (Isaiah [OTL; Louisville, Ky.: Westminster John Knox, 2001]), it marks a welcome return to the practice of commenting on the whole of the book, rather than, as became almost the invariable rule during the bulk of the twentieth century, of dividing the book between two or even three different commentators, following the broadly accepted historical-critical divisions of the book. As would be expected, Blenkinsopp’s general approach remains unchanged through the three volumes. Unlike some contributors to the Anchor Hebrew Studies 45 (2004) 329 Reviews Bible, he does not aim at a comprehensive discussion nor at length as a selfevident virtue. Rather, he focuses primarily on what might be called a detailed introduction to the book as a whole and in all its parts, with only brief and necessary textual notes and a running exposition of each paragraph which may not attend to every aspect and detail. Nevertheless, even within this uniformity, the tendency to greater detail as he has progressed is evident, and it surely cannot be wholly ascribed to the requirements of the material under discussion. In the first volume, the commentary proper (i.e., excluding introduction, bibliography, and so on) on the first thirty-nine chapters of the book averaged just over eight printed pages per chapter; in the second volume, the sixteen chapters of Deutero-Isaiah (40–55) received an average of twelve and a quarter pages each, and in the present volume this has risen again to about seventeen pages. It is noteworthy both that the textual notes are slightly fuller and in particular that, though the running style of general comment is retained, the format approximates more closely to that of a verse-by-verse approach than was previously the case. This is to be welcomed. Even so, Blenkinsopp clearly knows a great deal more than he has chosen to include, as witness a comparison, for instance, of his comments here on 66:17 with his recent article on the same verse, “The One in the Middle,” in Reading from Right to Left...

A NOVEL RUNNING STYLE IS ASSOCIATED WITH LOWER ECCENTRIC LOAD OF THE KNEE

It is generally accepted that running style is a learned response, that results in the lowest mechanical stress on the musculoskeletal tissues of the lower limb. The aim of this study was to determine if lower limb biomechanical variables in runners with a natural heel-toe running style change when coached to modify their running style. Twenty (20) natural heel-toe (HT) runners were instructed (4 hrs per week for 1 week) to run using a novel method (NM) running style characterized by a vertical alignment of the shoulders and hips with the support leg, while standing on the ball of the foot and by falling forward when transferring weight from one limb to the other. Gait analysis was performed on the group during running at their preferred speed using the Oxford metric Vicon Motion Analysis System and the Helen Hayes modified marker set. The biomechanical variables compared for the group across the 2 running styles were: stride length (m), contact time (s), vertical oscillation of the sacrum and heel (m), loading rate (N/s) and knee eccentric work (Joules/kg). The NM running style was characterized by significantly (p < 0.05) shorter stride length (m) (HT: 2.20±0.56, NM: 1.48±1.04), decreased contact time (s) (HT: 0.27±0.03, NM: 0.25±0.03), decreased heel (HT: 0.38±0.11, NM: 0.28±0.21) and sacral vertical oscillations (m) (HT: 0.09±0.03, NM: 0.05±0.04), and reduced knee eccentric load (J/kg) (HT: 0.47±0.15 J/kg, NM: 0.16±0.08). Runners that naturally adopt HT running can alter their running style by training to adopt a novel style that significantly alters biomechanical variables, which could result in a reduced risk of running injury and improve running economy.

Runner's stride analysis: comparison of kinematic and kinetic analyses under field conditions

Introduction – The purpose of this study was to identify the specific events in the gait cycle of a runner on the cranial–caudal, anterior–posterior and median–lateral acceleration curves obtained with an accelerometer system (Locométrix). Synthesis of facts – The strides of seven middle distance runners were analysed by using the 3D lumbar acceleration recordings synchronised with a video recording. Specific events, such as initial contact, mid stance and toe-off, were readily identified on the acceleration curves. The median–lateral acceleration curve enabled the right and left steps to be identified. Conclusion – Practical biomechanics information on an athlete's running style could be provided to the trainer by this new apparatus.

Lizard Locomotion: How Morphology Meets Ecology

Biological evolution often leads, through natural selection, to an optimal fit between 'design' and ecology. However, the adaptation process may be impeded or slowed down by several constraints or trade-offs between conflicting functions. This is frequently observed by ecomorphological studies focusing on lower taxonomic levels: form-function relationships get blurred because subtle adaptive traits remain hidden or simply do not exist. Therefore, a rigorous analytic approach is required, (ideally) assessing the links between the four stages of the adaptive process simultaneously (i.e., from genetic variation to variation in design, to variation in performance, to differential fitness), taking into consideration all potential factors hindering the normal progression of this process. Lizard locomotion is a good model for such an analysis. Locomotion is essential in many ecologically relevant functions (feeding, predator avoidance, etc.). It consists of several components (speed, acceleration, endurance, manoeuvrability, etc.) and modes (level running, climbing, etc.) with conflicting demands, leading to potential trade-offs. Moreover, several of its components proved to be heritable and obvious relations between habitat use and locomotor design are often absent (e.g., in lacertid lizards). Two cases, focusing on the potential trade-off between climbing and level-running, are presented to illustrate the subtle interplay between variation in ecology, performance and design in lizard locomotion. (1) For two gekkotans (a climber and a ground dwelling species) the moments exerted by several important leg muscles appear to be tuned to their primary mode of locomotion. (2) In two sibling lacertid species, the inverse trade-off between climbing and running, put forward on the basis of observed substrate use, does not exist. Instead, a drastic difference in running performance, likely related to different running styles, emerged. The latter case illustrates the potential use of 'integrated, dynamic design traits' as an intermediate stage between variation in design and performance.

Functional morphology of the hindlimb musculature of the black-billed magpie, Pica pica (Aves, Corvidae)

In spite of the ecological relevance of terrestrial locomotion for many bird species, this function remains poorly studied to date. Gait preferences and transitions seem present, but it is not known which factors might determine the running style. Morphological and morphometric data needed for further biomechanical modelling are presented for the black-billed magpie (Pica pica), a species which walks, runs and hops. Detailed descriptions of the muscle–tendon systems and the attachment sites on the hindlimb skeleton are given. Pinnation angles, fibre lengths and muscle masses are determined. From the latter two, physiological cross-sections of the muscle bundles are calculated. Tendon ossifications are qualitatively scored. Further, information on the mechanical variables of the body segments are collected (i.e. mass, length, position of the centre of gravity and moment of inertia of digits, tarsometatarsus, lower leg, upper leg, body, and head/neck). Moment arms of the important muscles powering terrestrial locomotion are discussed and, for some upper leg muscles, an equation to calculate the moment arms as a function of knee and hip joint angles is presented. All these data are indispensable for further kinesiological research.

The Influence of Heel Lift Manipulation on Achilles Tendon Loading in Running

In this study, a modeling method was developed to estimate Achilles tendon forces in running. Owing to the common use of heel lift devices in the treatment of Achilles tendon injury, we investigated the influence of increased heel lift on Achilles tendon loading. The hypothesis was that heel lift manipulation can influence maximum Achilles tendon force. Responses to heel lift variation were found to differ among 3 elite runners demonstrating distinct running styles. A rearfoot and a midfoot striker demonstrated significant increases in maximum Achilles tendon force with increased heel lift, whereas a forefoot striker demonstrated no changes in maximum Achilles tendon force values with heel lift manipulation (p&lt; .05). Analysis of the factors contributing to the observed changes in maximum Achilles tendon force highlighted the influence of the moment arm of ground reaction force and the moment arm of the Achilles tendon about the ankle joint center. The finding that increased heel lift may increase maximum Achilles tendon force suggests that caution is advised in the routine use of this intervention. The different responses to heel lift increase between subjects highlight the importance of classifying subjects based on running style.

"Leg spring" characteristics and the aerobic demand of running.

By applying a simple, linear mass-spring model to running, the normalized leg spring stiffness (Kleg), the normalized effective vertical stiffness (Kvert), and the mass-specific mechanical power output of the spring (Psp) were determined and correlated with aerobic demand. The purpose of the study was to determine whether leg spring characteristics explain any of the interindividual variability observed in aerobic demand at a given submaximal running speed. Recreational runners (N = 16) ran on a treadmill at 3.35 m x s(-1) for physiological measures and overground for biomechanical measures. The latter included a sagittal plane video record of the running motion and ground reaction data. We found no relationship between the aerobic demand of running and Kleg (r = -0.18), an inverse relationship between aerobic demand and Kvert (r = -0.48), and a positive correlation between aerobic demand and Psp (r = 0.45). The inverse relationship between Kvert and aerobic demand indicates that less economical runners possess a more compliant running style during ground contact. This running style may place greater force demands on extensor musculature.

Variation in morphology, gait characteristics and speed of locomotion in two populations of lizards

Locomotor behaviour varies between two subspecies of the Spanish wall lizardPodarcis hispanica.One subspecies inhabits the Columbretes islands, the other lives on the Spanish mainland. Size standardized voluntary speeds (as measured in unrestrained laboratory conditions) are lower in the island population (P. h. atrata) than in the mainland population (P. h. hispanica). Maximal running performance (when chased) is much higher in the mainland population than in the island population. High speed video recordings show that subspecies differ in gait characteristics: individuals from the mainland modulate running velocity primarily by modifying stride length, individuals from the island primarily by altering stride frequency.P. h. hispanica's strategy for modulating speed probably allows this mainland subspecies to attain higher maximal speeds than the island subspeciesP. h. atrata. Theoretical considerations suggest that at high speeds,P. h. hispanica's running style is energetically more favourable, but this hypothesis awaits experimental verification. We suggest that the differences in locomotion efficiency between the subspecies result from differences in predation pressure between the mainland and the island. The mainland study site has a higher predator diversity and offers less hiding opportunities to the lizards.

Perceptual and biomechanical variables for running in identical shoe constructions with varying midsole hardness

Objective. Perceptual ratings of mechanical variables were compared with biomechanical variables that are related to running injuries. Design. Eight identical running shoes with a relatively close range of midsole hardness were used. Ground reaction force (GRF), in-shoe pressure distribution and rearfoot motion were measured during running. Perceptual ratings were obtained after the running trials. Background. Previous studies reported high correlations between cushioning perception and biomechanical variables for shoes that featured large differences in midsole hardness. Methods. A 15-point categorical rating scale was used to judge impact severity, pressure magnitude and rearfoot motion in running. Rating scores were compared with biomechanical variables (GRF, pressure distribution and pronation values) using regression analyses. Results. Regression analyses revealed high relations between different biomechanical variables and the perception scores. The best relation to perception was analysed for the median power frequency of the vertical GRF ( r 2 = 0.97). A negative correlation ( r 2 = 0.54) between the first impact of GRF and the perception of impact severity could be revealed. Conclusion. The present study suggests that the body's sensory system seems to differentiate well between impacts of different frequency content. Based on perceptual abilities, subjects adapt their running style to avoid high heel impacts.

Biomechanical Events in the Time to Exhaustion at Maximum Aerobic Speed

Recent studies reported good intra-individual reproducibility, but great inter-individual variation in a sample of elite athletes, in time to exhaustion (t lim) at the maximal aerobic speed (MAS: the lowest speed that elicits V̇O 2max in an incremental treadmill test). The purpose of the present study was, on the one hand, to detect modifications of kinematic variables at the end of the t lim of the V̇O 2max test and, on the other hand, to evaluate the possibility that such modifications were factors responsible for the inter-individual variability in t lim. Eleven sub-elite male runners (Age = 24 ± 6 years; V̇O 2max = 69.2 ± 6.8 ml kg –1 min –1; MAS = 19.2 ± 1.45 km h –1; t lim = 301.9 ± 82.7 s) performed two exercise tests on a treadmill (0% slope): an incremental test to determine V̇O 2max and MAS, and an exhaustive constant velocity test to determine t lim at MAS. Statistically significant modifications were noted in several kinematic variables. The maximal angular velocity of knee during flexion was the only variable that was both modified through the t lim test and influenced the exercice duration. A multiple correlation analysis showed that t lim was predicted by the modifications of four variables (R = 0.995, P < 0.01). These variables are directly or indirectly in relation with the energic cost of running. It was concluded that runners who demonstrated stable running styles were able to run longer during MAS test because of optimal motor efficiency.

Metabolic responses and mechanisms during water immersion running and exercise.

The low impact nature of exercise in the water has increased interest in this form of exercise and specifically in water running as a cross-training modality. It is used as a possible preventative and therapeutic modality for rehabilitation. The high impact nature of land running predisposes the runner to stress of the lower limbs and overuse injuries. The need to reduce impact, as well as provide a low impact or non-weight-bearing condition for rehabilitation, has led runners and their coaches to the water. This increased interest by coaches and their athletes, attending sports medicine physicians and rehabilitative professionals has stimulated research into water immersion to the neck (WI) running. Exercise in the water has long been used by rehabilitative professionals with patients who have physically debilitating conditions (i.e. arthritis, musculoskeletal disorders) as it provides a medium for even those with limited mobility to exercise and relax their muscles. Numerous comparative studies into WI running from a metabolic as well as a training perspective have been published. WI has also long been used to simulate weightlessness for the comparative study of cardiorespiratory function and thermoregulation. WI and the associated cephalad shift in blood volume has implications on exercise responses during WI running exercise. In addition, the non-weight-bearing nature of WI running also raises issues of the cross-training benefits of WI running. WI running style and prior familiarity with the activity have been found to have a direct relationship with the comparability of WI to land running. This review presents current research into WI running, training specificity and comparative physiology.