Can We Rely on Mobile Devices and Other Gadgets to Assess the Postural Balance of Healthy Individuals? A Systematic Review.

The consequences of falls, costs, and complexity of conventional evaluation protocols have motivated researchers to develop more effective balance assessments tools. Healthcare practitioners are incorporating the use of mobile phones and other gadgets (smartphones and tablets) to enhance accessibility in balance evaluations with reasonable sensitivity and good cost-benefit. The prospects are evident, as well as the need to identify weakness and highlight the strengths of the different approaches. In order to verify if mobile devices and other gadgets are able to assess balance, four electronic databases were searched from their inception to February 2019. Studies reporting the use of inertial sensors on mobile and other gadgets to assess balance in healthy adults, compared to other evaluation methods were included. The quality of the nine studies selected was assessed and the current protocols often used were summarized. Most studies did not provide enough information about their assessment protocols, limiting the reproducibility and the reliability of the results. Data gathered from the studies did not allow us to conclude if mobile devices and other gadgets have discriminatory power (accuracy) to assess postural balance. Although the approach is promising, the overall quality of the available studies is low to moderate.

A Lactate Kinetics Method for Assessing the Maximal Lactate Steady State Workload.

During a continuously increasing exercise workload (WL) a point will be reached at which arterial lactate accumulates rapidly. This so-called lactate threshold (LT) is associated with the maximal lactate steady state workload (MLSSW), the highest WL, at which arterial lactate concentration [LA] does not change. However, the physiological range in which the LT and the MLSSW occur has not been demonstrated directly. We used minor WL variations in the MLSSW range to assess arterial lactate kinetics in 278 treadmill and 148 bicycle ergometer exercise tests. At a certain workload, minimal further increment of running speed (0.1-0.15 m/s) or cycling power (7-10 W) caused a steep elevation of [LA] (0.9 ± 0.43 mM, maximum increase 2.4 mM), indicating LT achievement. This sharp [LA] increase was more pronounced when higher WL increments were used (0.1 vs. 0.30 m/s, P = 0.02; 0.15 vs. 0.30 m/s, P < 0.001; 7 vs. 15 W, P = 0.002; 10 vs. 15 W, P = 0.001). A subsequent workload reduction (0.1 m/s/7 W) stopped the [LA] increase indicating MLSSW realization. LT based determination of running speed (MLSSW) was highly reproducible on a day-to-day basis (r = 0.996, P < 0.001), valid in a 10 km constant velocity setting (r = 0.981, P < 0.001) and a half marathon race (r = 0.969, P < 0.001). These results demonstrate a fine-tuned regulation of exercise-related lactate metabolism, which can be reliably captured by assessing lactate kinetics at the MLSSW.

Shank Muscle Strength Training Changes Foot Behaviour during a Sudden Ankle Supination.

BACKGROUND: The peroneal muscles are the most effective lateral stabilisers whose tension braces the ankle joint complex against excessive supination. The purpose of this study was to identify the morphological and biomechanical effects of two machine-based shank muscle training methods. METHODS: Twenty-two healthy male recreationally active sports students performed ten weeks of single-set high resistance strength training with 3 training sessions per week. The subjects conducted subtalar pronator/supinator muscle training (ST) with the right leg by using a custom-made apparatus; the left foot muscles were exercised with machine-based talocrural plantar and dorsiflexor training (TT). Muscle strength (MVIC), muscle volume and foot biomechanics (rearfoot motion, ground reaction forces, muscle reaction times) during a sudden ankle supination were recorded before and after the intervention. RESULTS: Compared to TT, ST resulted in significantly higher pronator (14% vs. 8%, P<0.01) and supinator MVIC (25% vs. 12%, P<0.01). During sudden foot inversions, both ST and TT resulted in reduced supination velocity (-12%; P<0.01). The muscle reaction onset time was faster after the training in peroneus longus (PL) (P<0.01). Muscle volume of PL (P<0.01) and TA (P<0.01) increased significantly after both ST and TT. CONCLUSION: After both ST and TT, the ankle joint complex is mechanically more stabilised against sudden supinations due to the muscle volume increase of PL and TA. As the reduced supination velocities indicate, the strength training effects are already present during free-fall. According to a sudden ankle supination in standing position, both machine-based dorsiflexor and pronator strength training is recommended for enhancing the mechanical stability of the ankle.

A whole body vibration perception map and associated acceleration loads at the lower leg, hip and head.

Whole-body vibration (WBV) training has become popular in recent years. However, WBV may be harmful to the human body. The goal of this study was to determine the acceleration magnitudes at different body segments for different frequencies of WBV. Additionally, vibration sensation ratings by subjects served to create perception vibration magnitude and discomfort maps of the human body. In the first of two experiments, 65 young adults mean (± SD) age range of 23 (± 3.0) years, participated in WBV severity perception ratings, based on a Borg scale. Measurements were performed at 12 different frequencies, two intensities (3 and 5 mm amplitudes) of rotational mode WBV. On a separate day, a second experiment (n = 40) included vertical accelerometry of the head, hip and lower leg with the same WBV settings. The highest lower limb vibration magnitude perception based on the Borg scale was extremely intense for the frequencies between 21 and 25 Hz; somewhat hard for the trunk region (11-25 Hz) and fairly light for the head (13-25 Hz). The highest vertical accelerations were found at a frequency of 23 Hz at the tibia, 9 Hz at the hip and 13 Hz at the head. At 5 mm amplitude, 61.5% of the subjects reported discomfort in the foot region (21-25 Hz), 46.2% for the lower back (17, 19 and 21 Hz) and 23% for the abdominal region (9-13 Hz). The range of 3-7 Hz represents the safest frequency range with magnitudes less than 1 g(*)sec for all studied regions.

Biomechanical and functional indicators in male semiprofessional soccer players with increased hip alpha angles vs. amateur soccer players.

BACKGROUND: Femoroacetabular impingement (FAI) is predominant in young male athletes, but not much is known about gait differences in cases of increased hip alpha angles. In our study, the hip alpha angle of Nötzli of soccer players was quantified on the basis of magnetic resonance imaging (MRI) with axial oblique sequences. The aim of the current study was to compare the rearfoot motion and plantar pressure in male semiprofessional soccer players with increased alpha angles to age-matched amateur soccer players. METHODS: In a prospective analysis, male semiprofessional and amateur soccer players had an MRI of the right hip to measure the alpha angle of Nötzli. In a biomechanical laboratory setting, 14 of these participants in each group ran in two shoe conditions. Simultaneously in-shoe pressure distribution, tibial acceleration, and rearfoot motion measurements of the right foot were performed. RESULTS: In the semiprofessional soccer group, the mean value of the alpha angle of group was 55.1 ± 6.58° (range 43.2-76.6°) and 51.6 ± 4.43° (range 41.9-58.8°) in the amateur group. In both shoe conditions, we found a significant difference between the two groups concerning the ground reaction forces, tibial acceleration, rearfoot motion and plantar pressure parameters (P < 0.01, P < 0.05, P = 0.04). Maximum rearfoot motion is about 22% lower in the semiprofessional group compared to the amateur group in both shoe conditions. CONCLUSIONS: This study confirmed that semiprofessional soccer players with increased alpha angles showed differences in gait kinematics compared to the amateur group. These findings support the need for a screening program for competitive soccer players. In cases of a conspicuous gait analysis and symptomatic hip pain, FAI must be ruled out by further diagnostic tests.

Effects of textured insoles on balance in people with Parkinson's disease.

BACKGROUND: Degradation of the somatosensory system has been implicated in postural instability and increased falls risk for older people and Parkinson's disease (PD) patients. Here we demonstrate that textured insoles provide a passive intervention that is an inexpensive and accessible means to enhance the somatosensory input from the plantar surface of the feet. METHODS: 20 healthy older adults (controls) and 20 participants with PD were recruited for the study. We evaluated effects of manipulating somatosensory information from the plantar surface of the feet using textured insoles. Participants performed standing tests, on two different surfaces (firm and foam), under three footwear conditions: 1) barefoot; 2) smooth insoles; and 3) textured insoles. Standing balance was evaluated using a force plate yielding data on the range of anterior-posterior and medial-lateral sway, as well as standard deviations for anterior-posterior and medial-lateral sway. RESULTS: On the firm surface with eyes open both the smooth and textured insoles reduced medial-lateral sway in the PD group to a similar level as the controls. Only the textured insole decreased medial-lateral sway and medial-lateral sway standard deviation in the PD group on both surfaces, with and without visual input. Greatest benefits were observed in the PD group while wearing the textured insoles, and when standing on the foam surface with eyes closed. CONCLUSIONS: Data suggested that textured insoles may provide a low-cost means of improving postural stability in high falls-risk groups, such as people with PD.

The influence of soccer shoe design on player performance and injuries.

Although soccer is the most popular sport in the world, little research has been published in the field of soccer biomechanics, particularly on the importance of footwear for the game. The traction properties of soccer shoes on natural and artificial turf have been speculated to be responsible for acute and chronic injuries in soccer. This article reviewed the current knowledge on how soccer shoes influence the risk of injuries and how they may serve to improve player performance. Comfort is the highest priority that players want from their shoes, followed by traction and stability. Cleat design and arrangement are important shoe features that allow for fast accelerations and stops, rapid cuts, and turns. Soccer shoe design can influence shooting speed and, even more important for the game of soccer, kicking accuracy. To combine shoe characteristics for injury prevention and better performance will be a challenge for future research on optimizing soccer shoes.

Lower and upper extremity loading in nordic walking in comparison with walking and running.

Nordic walking (NW) was compared with walking (W) and running (R) with respect to upper and lower limb injury risks. 24 NW-instructors performed W, NW, and R trials on a runway covered with artificial turf at controlled speeds. Foot pronation and ground reaction forces were measured as well as shock wave transmission to the right wrist. Comparison of NW and W shows similar results for all of the four chosen velocities (5 km/h, 7 km/h, 8 km/h, 8.5 km/h). Except for the 2nd peak of the vertical ground reaction force, NW results in higher loading rates and horizontal forces as well as higher pronation and pronation velocity values as compared with W. Wrist acceleration values up to 7.6 times gravitational acceleration were recorded in NW. Compared with R at the same speeds (8 km/h and 8.5 km/h), NW can be recommended as low impact sport with 36% lower loading rates and 59% lower pronation velocities. However, the high wrist accelerations in NW reveal that the upper extremities are exposed to considerable repetitive shocks, which may cause overuse injuries of the upper extremities. Thus, additional preventive exercises for the upper limb muscles are recommended as well as using shock absorbing walking poles.

Effects of different shoe-lacing patterns on dorsal pressure distribution during running and perceived comfort.

The purpose of this study was to investigate the effects of four lacing patterns (one regular, one tight, and two seven-eyelet lacings) on dorsal foot pressures during running and the perception of comfort and stability with 14 male rearfoot runners. By using a pressure insole, peak dorsal pressures were measured under the shoe's tongue. Highest peak pressures were found above the talus, the navicular bone, and the first ray. Seven-eyelet lacings showed a significant enhancement of perceived stability without differences in perceived comfort compared with a regular six-eyelet technique. Reduction of pressure on the talus, the navicular bone, and the extensor tendons is related to better comfort. With individually chosen special seven-eyelet lacings runners can improve foot-shoe coupling without increasing peak dorsal pressures on the tarsus. Knowledge of the location of the dorsal pressure distribution is useful for new tongue and lacing constructions to improve comfort in running shoes while maintaining stability.

A comparison of lower limb EMG and ground reaction forces between barefoot and shod gait in participants with diabetic neuropathic and healthy controls.

BACKGROUND: It is known that when barefoot, gait biomechanics of diabetic neuropathic patients differ from non-diabetic individuals. However, it is still unknown whether these biomechanical changes are also present during shod gait which is clinically advised for these patients. This study investigated the effect of the participants own shoes on gait biomechanics in diabetic neuropathic individuals compared to barefoot gait patterns and healthy controls. METHODS: Ground reaction forces and lower limb EMG activities were analyzed in 21 non-diabetic adults (50.9 +/- 7.3 yr, 24.3 +/- 2.6 kg/m2) and 24 diabetic neuropathic participants (55.2 +/- 7.9 yr, 27.0 +/- 4.4 kg/m2). EMG patterns of vastus lateralis, lateral gastrocnemius and tibialis anterior, along with the vertical and antero-posterior ground reaction forces were studied during shod and barefoot gait. RESULTS: Regardless of the disease, walking with shoes promoted an increase in the first peak vertical force and the peak horizontal propulsive force. Diabetic individuals had a delay in the lateral gastrocnemius EMG activity with no delay in the vastus lateralis. They also demonstrated a higher peak horizontal braking force walking with shoes compared to barefoot. Diabetic participants also had a smaller second peak vertical force in shod gait and a delay in the vastus lateralis EMG activity in barefoot gait compared to controls. CONCLUSIONS: The change in plantar sensory information that occurs when wearing shoes revealed a different motor strategy in diabetic individuals. Walking with shoes did not attenuate vertical forces in either group. Though changes in motor strategy were apparent, the biomechanical did not support the argument that the use of shoes contributes to altered motor responses during gait.

Plantar pressures during shod gait in diabetic neuropathic patients with and without a history of plantar ulceration.

BACKGROUND: Diabetic neuropathy leads to progressive loss of sensation, lower-limb distal muscle atrophy, autonomic impairment, and gait alterations that overload feet. This overload has been associated with plantar ulcers even with consistent daily use of shoes. We sought to investigate and compare the influence of diabetic neuropathy and plantar ulcers in the clinical history of diabetic neuropathic patients on plantar sensitivity, symptoms, and plantar pressure distribution during gait while patients wore their everyday shoes. METHODS: Patients were categorized into three groups: a control group (CG; n=15), diabetic patients with a history of neuropathic ulceration (DUG; n=8), and diabetic patients without a history of ulceration (DG; n=10). Plantar pressure variables were measured by Pedar System shoe insoles in five plantar regions during gait while patients wore their own shoes. RESULTS: No statistical difference between neuropathic patients with and without a history of plantar ulcers was found in relation to symptoms, tactile sensitivity, and duration of diabetes. Diabetic patients without ulceration presented the lowest pressure-time integral under the heel (72.1+/-16.1 kPa x sec; P=.0456). Diabetic patients with a history of ulceration presented a higher pressure-time integral at the midfoot compared to patients in the control group (59.6+/-23.6 kPaxsecx45.8+/-10.4 kPaxsec; P=.099), and at the lateral forefoot compared to diabetic patients without ulceration (70.9+/-17.7 kPa secx113.2+/-61.1 kPaxsec, P=.0193). Diabetic patients with ulceration also presented the lowest weight load under the hallux (0.06+/-0.02%, P=.0042). CONCLUSIONS: Although presenting a larger midfoot area, diabetic neuropathic patients presented greater pressure-time integrals and relative loads over this region. Diabetic patients with ulceration presented an altered dynamic plantar pressure pattern characterized by overload even when wearing daily shoes. Overload associated with a clinical history of plantar ulcers indicates future appearance of plantar ulcers.

Plantar pressure distribution patterns during gait in diabetic neuropathy patients with a history of foot ulcers.

OBJECTIVE: To investigate and compare the influence of a previous history of foot ulcers on plantar pressure variables during gait of patients with diabetic neuropathy. INTRODUCTION: Foot ulcers may be an indicator of worsening diabetic neuropathy. However, the behavior of plantar pressure patterns over time and during the progression of neuropathy, especially in patients who have a clinical history of foot ulcers, is still unclear. METHODS: Subjects were divided into the following groups: control group, 20 subjects; diabetic neuropathy patients without foot ulcers, 17 subjects; and diabetic neuropathy patients with at least one healed foot ulcer within the last year, 10 subjects. Plantar pressure distribution was recorded during barefoot gait using the Pedar-X system. RESULTS: Neuropathic subjects from both the diabetic neuropathy and DNU groups showed higher plantar pressure than control subjects. At midfoot, the peak pressure was significantly different among all groups: control group (139.4+/-76.4 kPa), diabetic neuropathy (205.3+/-118.6 kPa) and DNU (290.7+/-151.5 kPa) (p=0.008). The pressure-time integral was significantly higher in the ulcerated neuropathic groups at midfoot (CG: 37.3+/-11.4 kPa.s; DN: 43.3+/-9.1 kPa.s; DNU: 68.7+/-36.5 kPa.s; p=0.002) and rearfoot (CG: 83.3+/-21.2 kPa.s; DN: 94.9+/-29.4 kPa.s; DNU: 102.5+/-37.9 kPa.s; p=0.048). CONCLUSION: A history of foot ulcers in the clinical history of diabetic neuropathy subjects influenced plantar pressure distribution, resulting in an increased load under the midfoot and rearfoot and an increase in the variability of plantar pressure during barefoot gait. The progression of diabetic neuropathy was not found to influence plantar pressure distribution.

Effects of different shoe-lacing patterns on the biomechanics of running shoes.

In the present study, we examined the influence of shoe lacing on foot biomechanics in running. Twenty experienced rearfoot runners ran in six different lacing conditions across a force platform at a speed of 3.3 m . s(-1). Foot pronation during contact, tibial acceleration, and plantar pressure distribution of the right leg were recorded. The test conditions differed in the number of laced eyelets (1, 2, 3, 6 or 7) and in lacing tightness (weak, regular or strong). The results show reduced loading rates (P < 0.05) and pronation velocities (P < 0.01) in the tightest and highest lacing conditions. The lowest peak pressures under the heel and lateral midfoot (P < 0.01) were observed in the high (seven-eyelet) lacing pattern. Regular six-eyelet cross-lacing resulted in higher loading rates (P < 0.05) and higher peak heel pressures (P < 0.01) than seven-eyelet lacing, without any significant differences in perceived comfort. The low lace shoe conditions resulted in lower impacts (P < 0.01) and lower peak pressures under metatarsal heads III and V (P < 0.01), which is probably induced by the foot sliding within the shoe. A firm foot-to-shoe coupling with higher lacing leads to a more effective use of running shoe features and is likely to reduce the risk of lower limb injury.

Plantar pressure distribution patterns during gait in diabetic neuropathy patients with a history of foot ulcers

OBJECTIVE: To investigate and compare the influence of a previous history of foot ulcers on plantar pressure variables during gait of patients with diabetic neuropathy. INTRODUCTION: Foot ulcers may be an indicator of worsening diabetic neuropathy. However, the behavior of plantar pressure patterns over time and during the progression of neuropathy, especially in patients who have a clinical history of foot ulcers, is still unclear. METHODS: Subjects were divided into the following groups: control group, 20 subjects; diabetic neuropathy patients without foot ulcers, 17 subjects; and diabetic neuropathy patients with at least one healed foot ulcer within the last year, 10 subjects. Plantar pressure distribution was recorded during barefoot gait using the Pedar-X system. RESULTS: Neuropathic subjects from both the diabetic neuropathy and DNU groups showed higher plantar pressure than control subjects. At midfoot, the peak pressure was significantly different among all groups: control group (139.4±76.4 kPa), diabetic neuropathy (205.3±118.6 kPa) and DNU (290.7±151.5 kPa) (p=0.008). The pressure-time integral was significantly higher in the ulcerated neuropathic groups at midfoot (CG: 37.3±11.4 kPa.s; DN: 43.3±9.1 kPa.s; DNU: 68.7±36.5 kPa.s; p=0.002) and rearfoot (CG: 83.3±21.2 kPa.s; DN: 94.9±29.4 kPa.s; DNU: 102.5±37.9 kPa.s; p=0.048). CONCLUSION: A history of foot ulcers in the clinical history of diabetic neuropathy subjects influenced plantar pressure distribution, resulting in an increased load under the midfoot and rearfoot and an increase in the variability of plantar pressure during barefoot gait. The progression of diabetic neuropathy was not found to influence plantar pressure distribution.

The influence of soccer shoes on kicking velocity in full-instep kicks.

Soccer shoes enhance the traction required by the stance leg but decrease the quality of the ball contact during full-instep kicking. Shoe features that influence ball velocity include traction, foot protection, foot rigidity, and toe box height. Upper material and general comfort potentially affect ball velocity. In contrast, shoe weight and outsole stiffness do not influence ball velocity.

Influence of racket properties on injuries and performance in tennis.

Racket properties may affect tennis elbow development. Shock and vibration to the arm is influenced by the location of ball impacts on the racket head, racket stiffness, and grip force. Beginners experience increased arm loads, and they hit the ball lower on the racket head. Tennis rackets behave differently during actual play compared with the performance predicted by physics.

The pathomechanics of plantar fasciitis.

Plantar fasciitis is a musculoskeletal disorder primarily affecting the fascial enthesis. Although poorly understood, the development of plantar fasciitis is thought to have a mechanical origin. In particular, pes planus foot types and lower-limb biomechanics that result in a lowered medial longitudinal arch are thought to create excessive tensile strain within the fascia, producing microscopic tears and chronic inflammation. However, contrary to clinical doctrine, histological evidence does not support this concept, with inflammation rarely observed in chronic plantar fasciitis. Similarly, scientific support for the role of arch mechanics in the development of plantar fasciitis is equivocal, despite an abundance of anecdotal evidence indicating a causal link between arch function and heel pain. This may, in part, reflect the difficulty in measuring arch mechanics in vivo. However, it may also indicate that tensile failure is not a predominant feature in the pathomechanics of plantar fasciitis. Alternative mechanisms including 'stress-shielding', vascular and metabolic disturbances, the formation of free radicals, hyperthermia and genetic factors have also been linked to degenerative change in connective tissues. Further research is needed to ascertain the importance of such factors in the development of plantar fasciitis.

The arch index: a measure of flat or fat feet?

BACKGROUND: Studies using footprint-based estimates of arch height have indicated that obesity results in a lowered medial longitudinal arch in children. However, the potentially confounding effect of body composition on indirect measures of arch height, such as the arch index, has not been investigated. METHODS: This study assessed the body composition of 12 male and 12 female adults (mean age: 39.9 +/- 8.1 years, height: 1.724 +/- 0.101 m; weight: 95.1 +/- 13.7 kg, and BMI: 31.9 +/- 3.0 kg/m(2)) using bioelectrical impedance analysis to produce a two-component model of fat mass (FM) and fat-free mass (FFM). The dynamic arch index also was determined from electronic footprints captured during gait using a capacitive pressure distribution platform with a resolution of 4 sensors/cm(2). RESULTS: While significant correlations were noted between FFM and the area of both the hindfoot (r =.75, p <.05) and forefoot (r =.72, p <. 05), the midfoot area was correlated only with FM (r =.54, p <.05). Similarly, the arch index was significantly correlated with the FM percentage (r =.67, p <.05). CONCLUSIONS: The findings of this pilot study suggest that body composition influences arch index values in overweight and obese subjects. Consequently, body composition may be a confounding factor in interpreting footprint based estimates of arch height and, as such, these estimates would best be used with supplementary measures of body composition.

The evolution and biomechanics of the human foot - applied research for footwear

The onset of mankind is associated with the development from quadrupedal to bipedal locomotion, freeing our hands to use tools and thus structuring our brain towards complex intellectual capabilities. During the evolution of mankind over the span of several hundred millions years the human foot was gradually formed from the fins of early fish to an efficient load bearing structure for standing, walking, running, and jumping. The flexible foot anatomy with 26 bones, numerous ligaments and muscles allows an active adaptation of this biomechanical structure to uneven surfaces during locomotion. The human foot guarantees a stable support to the body, attenuates potentially harmful impact shocks, and provides sensory information about the contact with the ground. Early footwear was born of the necessity to provide protection when moving over rough terrain in varying weather conditions. The function of modern casual and athletic footwear is to provide comfort and protection of the body during various everyday and sports activities. Foot anatomy of men and adults. Additional body weigth in obese patients and the loss of sensory function in diabetic and neuropathic feet require special shoes to prevent pressure sores and guarantee mobility. Pressure distribuition measurement techniques are useful in analysing the mechanical behaviour of the human foot during static and dynamic loading situations in adults, children and patient groups. The understanding of foot biomechanics and the specific demands of everyday and sports activities are essential in the design of adequate footwear. Biomechanical testing of athletic footwear is necessary to inform consumers about injury preventive and performance related properties of commercially available sport shoes.

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.