Engineering ((Vibrations)) " Summarizing and writing a constructive criticism of the attached paper

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Remember before u handle this work, this work is so important to me, so i will revise it many times before i turn it in and I will rate u depend on your work quality such as providing correct and full response and meet all requirements in the attached instructions. Please avoid the Lack of depth in your response and plagiarism bcz I’ll check it with the ((Turn it in website.))

I need the following:

1. write only about one page

2. The first-half (or so) of your review should provide a summary of the paper. This section should be labeled Summary.

3. The second-half (or so) of your review should provide constructive criticism of the paper. That is, discuss what the authors could have done to make the paper better. Also, note if there are any problems with the paper. Label this section Recommendations.

4. Do not repeat text or equations in your review unless absolutely necessary. Use of quotes for repeating text from the paper is required. Overuse is discouraged.

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ARTICLE IN PRESS Journal of Biomechanics 36 (2003) 1761–1769 Muscle activity reduces soft-tissue resonance at heel-strike during walking James M. Wakelinga,*, Anna-Maria Liphardta,b, Benno M. Nigga a b Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta Canada T2N 1N4 Institute for Training and Movement Science, German Sport University, Cologne, Carl-Diem-Weg 6, 50933 Koln, . Germany Accepted 28 May 2003 Abstract 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. r 2003 Elsevier Ltd. All rights reserved. Keywords: Vibration; EMG; Joint loading 1. Introduction Ground reaction forces act between the ground and the foot of a person during walking and running. Ground reaction forces typically have an impact peak after heel-strike due to the collision of the foot with the ground. The impact force occurs within 50 ms after first contact and causes shock waves to travel through both the soft-tissues and skeletal components of the body. The impact force should be expected to cause oscillations in the wobbling structures of the body, and the tissues may resonante if their natural frequencies are close to the frequency of the input force. It has been proposed that lower extremity muscle activity adapts to the impact force which occurs during *Corresponding author. Tel.: +1-403-220-7004; fax: +1-403-2843553. E-mail address: wakeling@kin.ucalgary.ca (J.M. Wakeling). 0021-9290/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0021-9290(03)00216-1 heel-strike in order to minimize soft-tissue resonance (Nigg et al., 1995). If such a situation occurs then it may be possible to use shoe materials to modify the impact force and thus vibration load on the body in order to cause specific alterations in the muscle activity and thus joint loading. Previous studies have shown that the hardness of a shoe midsole causes changes in the time to peak impact force at heel-strike (Light et al., 1980; Frederick et al., 1984; Nigg et al., 1987; Lafortune et al., 1996). This time and the associated loading rate are a correlate of the major frequency content of the impact force (typically 10–20 Hz for running) and thus indicate that different shoes will result in different vibration loads on the tissues. The natural frequencies of the softtissues in the lower extremity range between 10 and 50 Hz (Wakeling and Nigg, 2001a), and so may potentially resonate due to the heel-strike impacts. However, both the natural frequency and damping coefficients of the soft-tissues of the lower extremity ARTICLE IN PRESS 1762 J.M. Wakeling et al. / Journal of Biomechanics 36 (2003) 1761–1769 change with altered muscle activity (Wakeling and Nigg, 2001a), indicating that muscle has the capability to alter the vibration response of the soft-tissues and the potential to minimize the soft-tissue resonance. During controlled vibration experiments, it was shown that muscle activity was used to increase vibration damping when an input frequency approached the resonance frequency of the tissue (Wakeling et al., 2002a). It has been shown that lower extremity muscle activity does adapt to the altered impact forces during running with different shoe midsole materials (Wakeling et al., 2001b, 2002b). However, it has not been shown that the muscle adaptation which occurs in response to the impact force during walking and running is related to the soft-tissue vibration frequencies. The purpose of this experiment was to measure changes in the muscle activity and soft-tissue vibrations which occurred during walking with different shoe conditions. The hypothesis to be tested was that when the input frequency of the ground reaction force approached the vibration frequency of the soft-tissues then the muscle activity within those tissues would increase in order to minimize the vibrations. 2. Methods 2.1. Subjects Twenty male (age 26.971.0 yr; mass 78.2473.20 kg; mean7SEM) and 20 female (age 25.871.1 yr; mass 67.6171.60 kg) subjects were tested. The subjects were students at the University of Calgary. Subjects gave their informed, written, consent to participate in accordance with the University of Calgary’s Conjoint Health Research Ethics Board policy on research using human subjects. Muscle and soft-tissue masses within the lower extremity were estimated from a series of length, breadth and skin fold measurements using methods previously described (Wakeling et al., 2002a). 2.2. Protocol Subjects were instructed to walk at a brisk pace along a 20 m indoor track. A force plate (Kistler AG, Winterthur, Switzerland) was placed in the centre of the track, level with the ground. Initial trials determined the starting position, which would result in the fifth step of the right foot striking the force plate. During the experiment, subjects were requested not to focus on the position of the force plate. Timing lights, spanning the force plate, were used to measure the walking velocity. The timing of heel-strike was determined by an accelerometer attached to the heel-cup of the right shoe. The control condition was a hard-soled leather shoe (Asker Shore C 77, 320 g). A soft (Asker Shore C 28) heel-cup insert was used as the insert condition. This insert had mass 26.2 g, and a maximum thickness of 4.5 mm which compressed to approximately 1.5 mm with body weight. The starting condition was randomized. Each condition was tested in blocks of 10 consecutive trials. The blocks were tested in the order ABBAAB, where A and B represent the two different conditions. This block design was used to minimize bias in the results due to muscle fatigue. For each trial, data were collected from a standing posture for 2 s, a subsequent walk of 10 double paces, and a final 2 s stand. Data were analysed for the middle eight steps from each trial. 2.3. Outcome measures The ground reaction force, the myoelectric signals from the lower extremity muscles and the soft-tissue accelerations were recorded at 2400 Hz using a 12-bit data acquisition system. Soft-tissue vibrations were measured from the muscle bellies of the vastus lateralis, biceps femoris (long head), tibialis anterior and lateral gastrocnemius using skin-mounted tri-axial accelerometers (EGAX accelerometer, nominal frequency response 0–600 Hz; Entran devices). The axes were orientated to be parallel to the long axis of the segment, normal to the skin, and medio-lateral. Accelerometers (o5 g) were attached to the skin surface, 1 cm distal to the EMG electrode, using Hollister medical adhesive glue, and a stretch adhesive bandage preloaded the accelerometer to improve the congruence of motion with the soft-tissues (Wakeling and Nigg, 2001a, b). Myoelectric activity was recorded from the rectus femoris, biceps femoris (long head), tibialis anterior and lateral gastrocnemius muscles. Myoelectric activity was measured from the muscle bellies using round bipolar surface electrodes (Ag/AgCl) after removal of the hair and cleaning of the skin with isopropyl wipes. Each electrode was 10 mm in diameter and had an interelectrode spacing of 22 mm and was placed midway between the motor end plate and distal myotendinous junction. A ground electrode was placed on the lateral condyle of the knee. EMGs were preamplified at source (Biovision, Wehrheim, Germany). 2.4. Analysis Initial analysis showed high frequency oscillations (>300 Hz) in the vertical ground reaction forces. These oscillations were removed by a 100 Hz low-pass filter, and the mean ground reaction force calculated from the 30 trials for each subject-condition combination and the vertical impact force was quantified for each trial by its maximum loading rate, F’GRF;max ; and ARTICLE IN PRESS J.M. Wakeling et al. / Journal of Biomechanics 36 (2003) 1761–1769 Table 1 Coefficients for the wavelets used to analyze high- and low-frequency components from the myoelectric signal Frequency fc (Hz) s t (ms) Frequency band (Hz) High Low 30.91 150.95 0.0997 0.0302 2.1 7.1 12–63 71–274 Center-frequency fc ; scale s; time resolution t: its peak value, FGRF;max : An effective input frequency, fGRF , was estimated from four times the period between the maximum loading rate and the peak impact force. The mean tissue acceleration during the 2 s static standing period prior to each walking trial was subtracted from the acceleration records, to reference the accelerations to a vertical standing posture. The mean acceleration traces were calculated from the 240 steps from each subject-muscle-axis-condition combination. Inertial tissue forces were calculated for each direction from the product of the mean referenced acceleration in that direction and the soft-tissue mass. Inertial forces were quantified by their maximum absolute loading rate after heel-strike, the maximum and minimum peak forces surrounding the maximum inertial loading rate. The vibration frequency was estimated from twice the period between the maximum and minimum forces. Myoelectric signals were resolved into their intensities in time-frequency space using EMG specific wavelet techniques (von Tscharner, 2000). The intensity is the power of the EMG signal contained within a particular frequency band. The total intensity over the frequency band 11–432 Hz was calculated using a filterbank of 11 wavelets with time resolutions from 45 to 12 ms. The intensity was also calculated for specific high and low-frequency bands using two wavelets W ðf Þ which were defined as the following function of frequency, f :  fc s f W ðf Þ ¼ efc sðf =fc þ1Þ ; fc ð1Þ where fc is the centre frequency of the wavelet, and s is a scaling factor. Parameters defining these two wavelets are given in Table 1. The intensities at the high and lowfrequency bands were calculated in the same manner as the intensity for each wavelet from the previously reported filter-bank (von Tscharner, 2000). The mean intensity trace was calculated for the 240 steps from each subject-muscle-condition combination, and was calculated for 50 ms time windows before and after heel-strike for the total intensity, and for 10 ms time windows spanning 50 ms before to 50 ms after heelstrike for the high- and low-frequency bands. 1763 2.5. Statistics The effects of the shoe condition on the measures of the GRF, vibration and EMG were determined using multifactorial analyses of variance. In each test the subject identity and the shoe condition were used as factors. Relative changes in parameters between the shoe conditions were calculated as the difference between the insert and control relative to the control value. All tests were considered significant at the a ¼ 0:05 level. Mean values are presented with the standard error of sample mean (SEM). 3. Results The subjects walked at a velocity of 2.1070.01 m s1 (mean7SEM) with a stance duration of 54972 ms. Analysis of variance showed that there were significant differences in both the walking velocity and stance duration between subjects, however, there were no significant effects of the shoe condition on these parameters. 3.1. Ground reaction forces The vertical ground reaction force showed an impact peak at 22 ms, and this impact peak was followed by a second peak at 50 ms for 35 of the 40 subjects (Fig. 1A). The ground reaction forces then showed large and broad peaks which are characteristic of walking. Superimposed on this characteristic pattern there were oscillations of small magnitude and high frequency (>300 Hz). Parameters quantifying the impact peak were calculated after these high-frequency oscillations were filtered and are shown in Table 2. Analysis of variance of the GRF parameters showed that there were significant effects of the shoe condition on the loading rate (15.9% decrease for the insert condition), and the effective input frequency (9.4% decrease), however there were no significant effects of the shoe condition on the magnitude of the impact peak. 3.2. Soft-tissue vibrations Transient peaks of inertial force occurred in all softtissue groups after heel-strike (e.g. Figs. 2 and 3). The magnitude of the peak forces (Table 3) varied with their direction relative to the leg segment. When walking with the control condition, the mean vibration frequencies weighted by the magnitude of the peak inertial forces were 26.1371.02, 24.2671.28, 38.5471.16 and 28.6271.03 Hz (N ¼ 40) for the quadriceps, hamstrings, tibialis anterior and triceps surae soft-tissue groups, respectively. ARTICLE IN PRESS J.M. Wakeling et al. / Journal of Biomechanics 36 (2003) 1761–1769 1764 There were significant effects of the insert condition on the maximum inertial loading rate for 10 of the possible 12 tissue-direction combinations (Table 3) with a reduction in the maximum inertial loading rate with the insert condition (e.g. 23.3% for the axial direction in the tibialis anterior). There were significant effects of the insert condition on the maximum inertial force for five of the possible 12 tissue-direction combinations (reduction for the insert condition; greatest reduction of 19.5% for the axial direction in the tibialis anterior). There were significant effects of the insert condition on the vibration frequency for four of the possible 12 tissuedirection combinations (reduction for the insert condition; greatest reduction of 16.2% for the axial direction in the hamstrings). GRF [kN] 3.3. Myoelectric activity 0 200 GRF [kN] 400 600 Time [ms] (A) 1 0 50 Time [ms] (B) GRF [kN] The insert condition resulted in changes to the myoelectric activity for all four muscles tested (Fig. 4). Analysis of variance showed that there was no significant effect of the shoe condition for the total intensity for the rectus femoris in both the 50 ms windows before and after heel-strike. Significant effects of the shoe condition were observed for the total intensity for the biceps femoris, tibialis anterior and lateral gastrocnemius (increases in the total intensity with the insert condition; Fig. 4). 1 100 1 0 200 400 600 Time [ms] (C) Fig. 1. Vertical ground reaction force (GRF) during one stance phase of walking (A). The time around heel-strike is shown at a larger scale in B. Mean and standard error of sample mean of the vertical GRFs for 30 trials (C). Raw traces are shown in A and B, and filtered traces are used for B and C. Fig. 2. Inertial forces in the hamstrings for a 57 kg subject. Traces are shown for the control condition (black lines) and insert condition (grey lines), as mean7SEM (N ¼ 240). Heel-strike occurred at a time of 0. Table 2 Parameters describing the impact peak of the vertical ground reaction force Condition Loading rate, F’GRF;max (kN s1) Impact force, FGRF;max (kN s1) Time to peak force tGRF (ms) Input frequency, fGRF (Hz) Control Insert 63.8570.67 53.7070.57 1.03670.005 1.03670.005 22.2370.16 22.7070.19 34.8370.21 31.5770.21 Values are given as mean 7SEM (N ¼ 1192). ARTICLE IN PRESS J.M. Wakeling et al. / Journal of Biomechanics 36 (2003) 1761–1769 Fig. 3. Inertial forces in the triceps surae for a 57 kg subject. Traces are shown for the control condition (black lines) and insert condition (grey lines), as mean7SEM (N ¼ 240). Heel-strike occurred at a time of 0. ANOVA results showed the only significant decreases in the high-frequency myoelectric activity to occur at 40 to 30 ms and 10 to 0 ms for the rectus femoris, and for 50 to 30 ms for the tibialis anterior (Fig. 4). All other significant effects of shoe condition on the myoelectric frequency at the high- and low-frequency bands were for increases with the insert condition. The greatest changes in myoelectric activity occurred for the lateral gastrocnemius muscle (24% increase extending from 50 to +50 ms). The biceps femoris showed significant shoe increases in myoelectric activity which reached 15% for the interval 20 to +20 ms. The tibialis anterior showed a gradation from decreased activity before heel-strike to increased activity after heelstrike, with the change from decreasing to increasing intensity occurring approximately 20 ms later for the high- than for the low-frequency band. The shoe condition showed little significant effect on the myoelectric activity from the rectus femoris. 4. Discussion 4.1. Limitations to the experimental design Muscle force production during walking changes throughout a stride. The frequency and damping 1765 coefficients of the soft-tissues change with muscle force (Wakeling and Nigg, 2001a) and, therefore, will also be expected to change throughout the stride. If dynamic muscle force cannot be accurately predicted from myoelectric activity, then so too the frequency and damping coefficients cannot be accurately modelled throughout a stride. The purpose of this study was to investigate the soft-tissue vibrations immediately following heel-strike and so the soft-tissue vibrations were characterized by their inertial loading rate, peak inertial force and effective frequency. These measures are taken directly from the acceleration traces, and therefore can be made without invoking assumptions about the muscle-force-dependent changes in the vibrations which would have to be made for more complex modelling. The high- and low-frequency bands used for myoelectric analysis in this study (Table 1) were developed to have short time resolutions (o10 ms), and to resolve the frequency bands where distinct myoelectric signals have previously been observed in man (Wakeling et al., 2001a). The short time resolutions were necessary to minimize the effects of movement artefacts related to the heel-strike impact from the measured myoelectric activity. We can be confident that the resolved signal before heel-strike using the two-frequency band approach is independent of impact related artefacts. The presented results were similar to myoelectric intensities calculated using pooled high- and low-frequency bands (wavelets 2–3 and 6–8 from the filter-bank of 11 wavelets; time resolutions o40 ms), but confirm that changes in muscle pre-activation are a real effect. 4.2. Soft-tissue resonance The lower extremities experienced oscillating input forces (the ground reaction force) during walking (Fig. 1). The high-frequency oscillations measured in the ground reaction force (>300 Hz) are likely due to the resonance of the force plate and had frequencies an order of magnitude hi ...
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Constructive Criticism
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This article was investigating the effect of movement of the muscle located in the lower
part of the body on damping of soft-tissues resonant frequency experienced upon heel-strike
when walking or running. Mainly, the article was trying to d...

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