Biomedical subjects

Benno M Nigg

Publications and source records attributed to Benno M Nigg.

At least 19 recordsLinked to original sources

PubMed2006

Quantification of the input signal for soft tissue vibration during running.

Soft tissue compartment vibrations are initiated at heel-strike in heel-toe running. The concept of muscle tuning suggests that the body tries to minimize these vibrations with a muscle adaptation that changes the mechanical properties of the soft tissue compartment. A muscle tuning adaptation can be quantified by determining the biodynamic response, of the soft tissue compartment for different experimental conditions. To determine the biodynamic response a measure of both the input signal and the soft tissue compartment vibrations are required. The input signal for the vibrations is the rapid deceleration of the leg after initial ground contact. The aim of this study was to evaluate three non-invasive methods to quantify the input signal for the triceps surae soft tissue vibrations. Data from a force platform, a shoe mounted accelerometer and a video analysis of a reflective skin marker were used to quantify leg deceleration. Both the shoe mounted accelerometer and skin marker method provided a satisfactory evaluation of the input signal and could be used to determine the biodynamic response of the soft tissue compartment. The impact portion of the ground reaction force is primarily due to the deceleration of the leg at landing. However, due to the influence of the effective body mass on the impact magnitude, the force plate data was not appropriate for quantifying a muscle tuning response.

Computer Simulation↗

PubMed2006

Lower leg muscle atrophy in ankle osteoarthritis.

The aim of this study was to determine changes in the lower leg muscles associated with ankle osteoarthritis. Fifteen unilateral ankle osteoarthritis patients and fifteen age-gender-matched normal subjects were assessed with clinical [osteoarthritis latency time, pain, alignment, AOFAS ankle score, ankle range of motion (ROM), calf circumference], radiological (ankle osteoarthritis grading), and muscular-physiological parameters [isometric maximal voluntary ankle torque, surface electromyography of the anterior tibial (AT), medial gastrocnemius (MG), soleus (SO), and peroneus longus (PL) muscle]. The osteoarthritis patients had increased pain (6.8 points) and reduced AOFAS score (33.7 points) compared to the control group. Compared to the contralateral healthy leg, the arthritic leg showed reduced mean dorsi-/plantar flexion ROM (16.0 degrees), reduced mean calf circumference (2.1 cm), smaller mean dorsiflexion (16.4 Nm) and plantar flexion (15.8 Nm) torques, lower mean electromyography frequency for all muscles (AT -22.6 Hz; MG -27.3 Hz; SO -25.9 Hz; PL -28.5 Hz), and lower mean electromyography intensity in the AT [-28.0x10(3) (microv)2], MG [-13.3x10(3) (microv)2], and PL [-12.8x10(3) (microv)2]. SO mean electromyography intensity was not significantly changed [+2.0x10(3) (microv)2]. Unilateral ankle osteoarthritis is associated with atrophic changes of the lower leg muscles. This study supports previous observations on muscle dysfunction in knee osteoarthritis.

Adult↗

PubMed2006

Soft tissue vibrations within one soft tissue compartment.

The concept of muscle tuning suggests that vibrations of the soft tissue compartments of the leg initiated by impacts are minimized by muscular activity prior to heel-strike of heel-toe running. For the quantification of muscle tuning it has been assumed (1) that the soft tissue compartment acts as one lumped mass and (2) that vibration energy dissipation does occur within one muscle. The purpose of this study was to test these two assumptions. It was hypothesized that (H1) the movement of the soft tissue compartment is not homogeneous, (H2) the vibration frequencies for different muscles within one soft tissue compartment are different and (3) attenuation of vibration movement within one muscle does occur. Soft tissue vibrations were measured using accelerometers on four locations on the quadriceps soft tissue compartment during heel-toe running. There were differences in the peak soft tissue acceleration and time of peak acceleration between accelerometer locations. The dominant frequency was similar throughout the soft tissue compartment, however; there was an attenuation of high-frequency vibration energy between distal and proximal points overlying one muscle. This evidence suggests that accelerometer placement is important when quantifying the acceleration magnitude and timing of peak soft tissue compartment but not when estimating the resonant vibration characteristics of a soft tissue compartment. It also provides initial evidence to support the idea that vibration control through muscle tuning may be achieved through changes in energy dissipating properties within the soft tissue compartment.

Acceleration↗

PubMed2006

Muscle tuning during running: implications of an un-tuned landing.

BACKGROUND: The impact force in heel-toe running is an input signal into the body that initiates vibrations of the soft tissue compartments of the leg. These vibrations are heavily damped and the paradigm of muscle tuning suggests the body adapts to different input signals to minimize these vibrations. The objectives of the present study were to investigate the implications of not tuning a muscle properly for a landing with a frequency close to the resonance frequency of a soft tissue compartment and to look at the effect of an unexpected surface change on the subsequent step of running. METHOD: Thirteen male runners were recruited and performed heel-toe running over two surface conditions. The peak accelerations and biodynamic responses of the soft tissue compartments of the leg along with the EMG activity of related muscles were determined for expected soft, unexpected hard and expected hard landings. RESULTS AND CONCLUSIONS: For the unexpected hard landing there was a change in the input frequency of the impact force, shifting it closer to the resonance frequency of the soft tissue compartments. For the unexpected landing there was no muscle adaptation, as subjects did not know the running surface was going to change. In support of the muscle-tuning concept an increase in the soft tissue acceleration did occur. This increase was greater when the proximity of the input signal frequency was closer to the resonance frequency of the soft tissue compartment. Following the unexpected change in the input signal a change in pre-contact muscle activity to minimize soft tissue compartment vibrations was not found. This suggests if muscle tuning does occur it is not a continuous feedback response that occurs with every small change in the landing surface properties. In previous studies with significant adaptation periods to new input signals significant correlations between the changes in the input signal frequency and the EMG intensity have been shown, however, changes in soft tissue accelerations have not been found. The results of the present study showed that changes in these soft tissue accelerations can occur in response to a resonance frequency input signal when a muscle reaction has not happened.

Acceleration↗

PubMed2006

Unstable shoe construction and reduction of pain in osteoarthritis patients.

PURPOSE: The purposes of this study were to assess a) the effectiveness of Masai Barefoot Technology (MBT) shoe in reducing knee pain in persons with knee osteoarthritis (OA) and (b) changes in balance, ankle and knee ROM, and ankle strength compared with a high-end walking shoe for 12 wk. METHODS: The research design was a randomized controlled trial (123 subjects, knee OA). Subjects were randomized to a MBT (N = 57) or a control shoe (N = 66). A Western Ontario and McMaster Universities (WOMAC) OA index, BMI, balance, active ROM, and ankle torque were quantified at week 0, 3, 6, 9, and 12. Two-sample t-tests were done for between-group comparisons. RESULTS: There was no significant difference between groups in total pain score. A significant reduction over the 12-wk period was found for both shoe conditions (-42/500 or 25.6% MBT, -46.2 or 27.1% control). There was no significant group difference in pain during walking (t = -1.09, P = 0.28). Pain during walking was significantly reduced by 5.2/100 mm in the MBT and 9.7/100 mm in the control group. Total pain showed a significant reduction for the MBT -27.4/500 (-16.6%) and the control group -28.9/500 (-17.0%) between baseline and week 3. Between week 3 and 6, there was a significant reduction for the MBT group only (-27.2/500 or -20.0%). There was a significant increase in the static balance between baseline and 12 wk in the MBT group only, although the difference between groups was not significant. DISCUSSION: The results indicate that special shoe interventions can reduce pain in subjects with moderate knee OA.

Adult↗

PubMed2005

Foot orthoses affect frequency components of muscle activity in the lower extremity.

The purpose of this study was to quantify the effects of selected foot orthoses on muscle activity in the lower extremity during running. Nine male and 12 female recreational runners, clinically and functionally classified as 'pronators', volunteered for this study and performed over-ground running trials at 4m/s in each of four experimental conditions: control, posting, molding, and posting & molding. Electromyographic (EMG) signals were recorded from seven lower extremity muscles. Wavelet analysis was performed to obtain EMG intensities in two frequency bands that were averaged for the pre-heel-strike and post-heel-strike intervals and for 30-100% of stance phase. Posting and custom-molding of foot orthoses increased the global EMG intensity of most muscles of the lower extremity for the stance phase of running (P < 0.05). The increases in EMG intensity were greater in the high- than in the low-frequency bands for some lower extremity muscles (P < 0.05). The effects on muscle activity of posting and custom-molding of foot orthoses differed between the three phases of running gait. The three tested foot orthoses did affect lower extremity muscle activity differently and these effects were specific to the phases of running gait. Combinations of increased requirements of controlling joint motion and minimizing soft tissue vibrations may have led to greater increases in shank muscle activity for the posted condition. The substantial changes in EMG due to orthotic interventions found in this study documents the importance of the study of muscle activity as a reaction to shoe inserts and foot orthoses.

Adult↗

PubMed2005

Changing the texture of footwear can alter gait patterns.

The foot provides an important source of afferent feedback for balance and locomotion. Sensory feedback from the feet can be altered by standing or walking on different surfaces. The purpose was to determine the effects of textured footwear on lower extremity muscle activity, limb kinematics, and joint kinetics while walking. Three-dimensional kinematics and kinetics, as well as muscle EMG, were collected as subjects walked with a smooth and textured shoe insert. Muscle activity was analyzed using a wavelet technique. The textured shoe insert caused a significant reduction in both soleus and tibialis anterior intensity during periods when these muscles are most active. Furthermore, the changes in muscle activity were only seen in the low frequency content of the EMG signal. The foot was significantly more plantar flexed at heel strike with the textured inserts. Small changes were also seen in vertical ground reaction forces and joint moments. It was assumed that the changes in gait patterns were due to a change in sensory feedback caused by the textured shoe insert. The possibilities of altered sensory feedback with footwear are discussed. Sensory feedback from the feet may affect specific motor unit pools during different activities. Changing the texture, without changing the geometry, of a shoe insert can alter muscle activity during walking. This may be useful in the prescription of footwear interventions and suggests that footwear may have sensory as well as mechanical effects.

Adaptation, Physiological↗

PubMed2004

Muscle activity in the leg is tuned in response to impact force characteristics.

Based on results from quasi-static experiments, it has been suggested that the lower extremity muscle activity is adjusted in reaction to impact forces with the goal of minimizing soft-tissue vibrations. It is not known whether a similar muscle tuning occurs during dynamic activities. Thus, the purpose of this study was to determine the effect of changes in the input signal on (a) vibrations of lower extremity soft-tissue packages and (b) EMG activity of related muscles during heel-toe running. Subjects performed heel-toe running in five different shoe conditions. Ground reaction forces were measured with a KISTLER force platform, soft-tissue vibrations were measured with tri-axial accelerometers and muscle activity was measured using surface EMG from the quadriceps, hamstrings, tibialis anterior and triceps surae groups from 10 subjects. By changing both the speed of running and the shoe midsole material the impact force characteristics were changed. There was no effect of changes in the input signal on the soft-tissue peak acceleration following impact. A significant correlation (R2=0.819) between the EMG pre-activation intensity and the impact loading rate changes was found for the quadriceps. In addition, the input frequency was shown to approach the vibration frequency of the quadriceps. This evidence supports the proposed paradigm that muscle activity is tuned to impact force characteristics to control the soft-tissue vibrations.

Adult↗

PubMed2003

Changes in EMG signals for the muscle tibialis anterior while running barefoot or with shoes resolved by non-linearly scaled wavelets.

The purpose of this project was to study the EMG pattern of the tibialis anterior muscle in heel-toe running. Specifically, EMG changes in time, intensity and frequency shortly before and after heel-strike were addressed using an EMG-specific non-linearly scaled wavelets analysis. This method allowed extracting the time, intensity and frequency information inherent in the EMG signal at any time. The EMG signals of 40 male subjects were recorded for running barefoot and with shoes. The results confirmed that the pre-heel-strike EMG activities were typically seen at higher EMG frequencies (60-270Hz) while the post-heel-strike EMG activities resulted in lower frequency signals (10-90Hz). The timing of the pre-heel-strike EMG activities was not influenced by the used shoe conditions. The timing of the post-heel-strike EMG activities was significantly delayed when wearing shoes. The intensity of the pre-heel-strike muscle activity increased compared to the post-heel-strike one when wearing shoes. One can conclude that the activity of the tibialis anterior adjusts specifically to exterior conditions. The frequency shift between pre- and post heel-strike muscle activity were discussed with respect to activation of different motor units.

Adaptation, Physiological↗

PubMed2003

Muscle activity reduces soft-tissue resonance at heel-strike during walking.

Muscle activity has previously been suggested to minimize soft-tissue resonance which occurs at heel-strike during walking and running. If this concept were true then the greatest vibration damping would occur when the input force was closest to the resonant frequency of the soft-tissues at heel-strike. However, this idea has not been tested. The purpose of this study was to test whether muscle activity in the lower extremity is used to damp soft-tissue resonance which occurs at heel-strike during walking. Hard and soft shoe conditions were tested in a randomized block design. Ground reaction forces, soft-tissue accelerations and myoelectric activity were measured during walking for 40 subjects. Soft-tissue mass was estimated from anthropologic measurements, allowing inertial forces in the soft-tissues to be calculated. The force transfer from the ground to the tissues was compared with changes in the muscle activity. The soft condition resulted in relative frequencies (input/tissue) to be closer to resonance for the main soft-tissue groups. However, no increase in force transmission was observed. Therefore, the vibration damping in the tissues must have increased. This increase concurred with increases in the muscle activity for the biceps femoris and lateral gastrocnemius. The evidence supports the proposal that muscle activity damps soft-tissue resonance at heel-strike. Muscles generate forces which act across the joints and, therefore, shoe design may be used to modify muscle activity and thus joint loading during walking and running.

Acceleration↗

PubMed2003

Foot orthotics affect lower extremity kinematics and kinetics during running.

OBJECTIVE: To quantify the effects of posting and custom-molding of foot orthotics on lower extremity kinematics and kinetics during running. DESIGN: Repeated measures.Background. Several kinematic and kinetic factors have been suggested to increase a runner's risk for injuries. It has been speculated that foot orthotics can be used to reduce injury related complaints or even prevent running injuries by affecting these factors. METHODS: Twenty one volunteers participated in this study. Kinematic and kinetic variables obtained during overground running for medial posting, custom-molding, and the combination of medial posting and custom-molding of foot orthotics were compared to a control condition. Repeated measures ANOVA and student t-tests were used to detect significant differences (alpha=0.05). RESULTS: Posting of foot orthotics reduced maximum foot eversion and ankle inversion moment and increased vertical loading rate and maximum knee external rotation moment (P<0.05). Molding and posting and molding reduced vertical loading rate and ankle inversion moment and increased maximum foot inversion and maximum knee external rotation moment (P<0.05). CONCLUSIONS: The effects of posting and molding of foot orthotics are extremely different and when combining posting and molding, the effects of molding appear to be dominant. It yet remains to be determined whether posting or molding is more beneficial with respect to overuse running injuries. RELEVANCE: The potential of foot orthotics for reducing pain and injuries is convincing. The current study provides valuable information about the role of specific structural components of foot orthotics and contributes to the knowledge about the mechanism underlying the effect of foot orthotics in running.

Adult↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 1: Range of motion.

BACKGROUND: The purpose of this study was to determine how closely the present designs of ankle prostheses mimic the unique requirements of the foot and ankle. The three-dimensional range of motion (ROM) of the ankle joint complex, before and after ankle arthrodesis and after implantation of three currently used total ankle prostheses, was investigated. METHODS: The three-dimensional ROM was determined in six fresh-frozen cadaver leg specimens using a 6-df device with an axial load of 200 N and a four-camera high-speed video system. A moment of 100 Nm was applied to the footplate to determine the ROM in the sagittal (dorsiflexion and plantarflexion) and frontal (inversion and eversion) planes. The same moment was applied to the tibia to determine the ROM for the internal and external tibial rotation. The measurements were performed for the normal ankle, the fused ankle, and the AGILITY, HINTEGRA, and S.T.A.R. prostheses. RESULTS: Compared to the normal condition, the ROM for dorsiflexion and plantarflexion was changed for all surgical interventions. The changes were highest for the ankle arthrodesis. The changes due to the prostheses were significantly less than the changes due to ankle arthrodesis. Compared to the normal condition, the total ROM for inversion/eversion was slightly decreased by the fused ankle and not changed by the three-component prostheses (HINTEGRA, S.T.A.R.). However, the ROM for inversion/eversion was significantly higher for the two-component prosthesis, AGILITY. The ROM for internal and external tibial rotation was not altered by the AGILITY and HINTEGRA ankle, but it was significantly reduced by the ankle arthrodesis. S.T.A.R. showed a significant shift of the total ROM toward internal tibial rotation. CONCLUSIONS: The three tested ankle joint prostheses changed the ROM of the ankle joint complex less than ankle fusion did. Total ankle prostheses were shown to replicate normal joint ROM closely. However, ankle arthrodesis was found to reduce the ROM substantially in all three planes: the sagittal, frontal, and horizontal planes. CLINICAL IMPLICATIONS: With respect to the ROM, total ankle replacement changes the natural ankle joint condition less than ankle arthrodesis, which reduces the ROM in all three planes and might increase stress in adjacent structures. The prosthesis that replicated the normal ankle joint ROM best was the one with the most anatomical design.

Aged↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 2: Movement transfer.

INTRODUCTION: The purpose of this in vitro study was to determine the biomechanical characteristics of the ankle based on the movement transfer between foot and leg before and after ankle arthrodesis, and after implantation of three currently used total ankle prostheses. METHODS: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveric leg specimens. While the foot was moved through the range of dorsiflexion/plantarflexion, the resulting foot eversion/inversion and tibial rotation were recorded. Analogously, the resulting foot eversion/inversion from tibial rotation and, vice versa, the resulting tibial rotation from foot eversion/inversion were determined. The same measurements were performed for the normal ankle, the fused ankle, and after total ankle replacement by the AGILITY, HINTEGRA, and S.T.A.R. prostheses. RESULTS: While in dorsiflexion/plantarflexion of the foot, ankle joint fusion increased the movement transfer to tibial rotation by a 2.4 factor and to eversion/inversion by a 18.5 factor, whereas, this movement transfer did not change for all prostheses conditions. The movement transfer between foot eversion and tibial rotation was found to decrease for all ankle prostheses, but more in the AGILITY and S.T.A.R. prosthesis than in the HINTEGRA. CONCLUSIONS: The three tested ankle joint prostheses changed the movement transferred within the ankle joint complex less than ankle fusion did, especially for dorsiflexion/plantarflexion movement of the foot. The closer the design was to the normal anatomy of the ankle, the closer the transfer of movement was shown to be replicated with respect to normal joint. It is suggested that success of total ankle arthroplasty depends on how successfully designs can mimic the movement transfer of the normal ankle, while dissipating the rotational forces and maintaining the stability of the joint.

Aged↗

PubMed2003

Kinematic changes after fusion and total replacement of the ankle: part 3: Talar movement.

INTRODUCTION: The purpose of this study was to determine talar movement (e.g., talar rotation and talar shift during (dorsiflexion/plantarflexion) with respect to the tibia in the normal ankle, in the fused ankle, and in the replaced ankle by currently used prosthetic designs. METHODS: A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveri leg specimens. While moving the foot through the whole range of motion for plantarflexion/dorsiflexion, segmental motion of the marked bones of the foot and shank were measured dynamically. Rotation and medial-lateral shift of the talus were then calculated with regard to flexion position of the foot. RESULTS: In the normal ankle, plantarflexion movement was coupled with talar inversion of 3.5 degrees, and dorsiflexion movement with talar eversion of 1.0 degree, in totally accounting for 4.5 degrees of talar rotation. While both the HINTEGRA and the S.T.A.R. prostheses did not show changes to the normal condition during the dorsiflexion/plantarflexion cycle (p < .05), talar rotation had a 60% decrease (p < .05) for the AGILITY prosthesis. In the normal ankle joint, a lateral talar shift of 1.4 mm was found to occur during dorsiflexion, and a lateral talar shift of 5.2 mm during plantarflexion. In both, the HINTEGRA and S.T.A.R. ankles, talar shift was converted into medial direction during dorsiflexion of the foot (difference to normal: p < .05), whereas talar shift in the lateral direction was found to occur during plantarflexion of the foot which was comparable to the normal ankle. The AGILITY ankle evidenced an 80% decrease of talar shift (p < .05) during the whole dorsiflexion/plantarflexion cycle. DISCUSSION: The two-component ankle (AGILITY) obviously tends to restrict tremendously talar motion within the ankle mortise, whereas the three-component ankles (HINTEGRA, S.T.A.R.) seem to allow talar range of motion comparable to that in the normal ankle. It is suggested that such a restriction of talar motion results in an increase of stress forces within and around the prosthesis, leading to polyethylene wear and potential loosening at the bone-implant interfaces. Therefore, a successful prosthetic design for the ankle should consist of three components that are shaped as anatomically as possible to provide a normal range of motion and to allow the full transmission of movement transfer between foot and shank and unconstrained movement of the talus within the ankle mortise.

Aged↗

PubMed2003

Effect of shoe inserts on kinematics, center of pressure, and leg joint moments during running.

PURPOSE: The purposes of this project were to assess the effect of four different shoe inserts on the path of the center of pressure (COP), to quantify the effect of these inserts on selected knee joint moments during running, and to assess the potential of COP data to predict the effects of inserts/orthotics on knee joint moments. METHODS: Kinematics for the lower extremities, resultant ankle and knee joint moments, and the path of the COP were collected from the right foot of 15 male subjects while running heel-toe with five different shoe inserts (full or half with 4.5-mm postings). RESULTS: Individual movement changes with respect to the neutral insert condition were typically small and not systematic. Significant changes for the path of the COP were registered only for the full lateral insert condition with an average shift toward the lateral side. The mediolateral shift of the COP was not consistent for the full medial and the two half-shoe inserts. The subject-specific reactions to the inserts' intervention in the corresponding knee joint moments were typically not consistent. Compared with the neutral insert condition, subjects showed increases or decreases of the knee joint moments. The correlation between the individual COP shifts and the resultant knee joint moment was generally small. CONCLUSION: The results of this study showed that subject-specific reactions to the tested inserts were often not as expected. Additionally, reactions were not consistent between the subjects. This result suggests that the prescription of inserts and/or orthotics is a difficult task and that methods must be developed to test and assess these effects. Such methods, however, are not currently available.

Adult↗

PubMed2003

Orthotic comfort is related to kinematics, kinetics, and EMG in recreational runners.

PURPOSE: The purpose of this study was to determine the relationship between differences in comfort and changes in lower extremity kinematic and kinetic variables and muscle activity in response to foot orthoses. METHODS: Twenty-one recreational runners volunteered for this study. Three orthotic conditions (posting, custom-molding, and posting and custom-molding) were compared with a control (flat) insert. Lower extremity kinematic, kinetic, and EMG data were collected for 108 trials per subject and condition in nine sessions per subject for overground running at 4 m.s-1. Comfort for all orthotic conditions was assessed in each session using a visual analog scale. The statistical tests used included repeated measures ANOVA, linear regression analysis, and discriminant analysis (alpha = 0.05). RESULTS: Comfort ratings were significantly different between orthotic conditions and the control condition ([lower, upper] confidence limits; posting: [-3.1, -0.8]; molding: [0.4, 3.4]; and posting and molding: [-1.1, 1.9]); 34.9% of differences in comfort were explained by changes in 15 kinematic, kinetic, and EMG variables. The 15 kinematic, kinetic, and EMG variables that partially explained differences in comfort classified 75.0% of cases correctly to the corresponding orthotic condition. DISCUSSION: In general, comfort is an important and relevant feature of foot orthoses. Evaluations of foot orthoses using comfort do not only reflect subjective perceptions but also differences in functional biomechanical variables. Future research should focus on defining the relationship between comfort and biomechanical variables for material modifications of footwear, different modes of locomotion, and the general population.

Adult↗

PubMed2002

Development of a reliable method to assess footwear comfort during running.

The purposes of this study were: (a) to determine whether subjects are able to distinguish between differences in footwear with respect to footwear comfort; and (b) to determine how reliably footwear comfort can be assessed using a visual analogue scale (VAS) and a protocol including a control condition during running. Intraclass correlation coefficients (ICCs) between comfort ratings for repeated conditions were high (ICC = 0.799). Differences in comfort ratings between the insert conditions were significant. A paired t-test revealed a significant difference in overall comfort ratings for the control insert when tested after the soft insert compared to when tested after the hard insert (P = 0.008). The results of this study showed that VASs provide a reliable measure to assess footwear comfort during running under the conditions that: (a) a control condition is included; and (b) the average comfort rating of sessions 4-6 is used.

Adult↗

PubMed2002

Altering muscle activity in the lower extremities by running with different shoes.

PURPOSE: To provide evidence that lower-extremity muscle activity during running is tuned in response to the loading rate of the impact forces at heel-strike. METHODS: Six runners ran two 30-min trials per week for 4 wk. The trials tested two shoes which differed only in the material hardness of the midsole. The shoes were tested in a randomized sequence. Bipolar surface EMG was recorded from the muscles of the rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior. EMG was resolved into time-frequency space using wavelet techniques. EMG was analyzed for the 150 ms time window immediately before heel-strike. RESULTS: The intensity of the EMG and the ratio of the EMG intensity between high and low frequency components both showed significant changes between shoes, subjects, and muscles. Additionally, the intensity ratio showed a significant change over the course of each 30-min run. CONCLUSIONS: Lower-extremity muscle activity used to tune the muscles for the impact task can be altered by changing the material hardness of the shoe. The changes in the EMG frequency ratio suggest that muscle fiber-type recruitment patterns can also be altered by the choice of midsole material.

Adult↗