Kerrigan et al.,1998 and White et al., 1998
Introduction
Gait by definition is the manner of how humans or animals move from one point to another. This ‘travelling’ is done by movement of various joints at different points of time. It can be referred to walking or running pattern. “Walking involves progression by alternating periods of loading and unloading” (Wikipedia). Walking and running gaits can be divided into two main phases, namely the stance and swing phase. The time spent in these two phases varies greatly, being dependant on the velocity of movement. When walking, most time is spent in the stance phase and while running, most time is spent in the swing phase. This ensures a minimum contact time with the ground while producing larger ground reaction forces to propel the runner upward and forward with more velocity.
Technology can now be used to analyze gaits with piezoelectric plates that measure ground reaction forces and high frequency infrared cameras. This would be beneficial to individuals who are biomechanically challenged (e.g. flat foot, muscular imbalances and injuries). The results of gait analysis can then be used by physical therapists and doctors to improve performance of athletes and also quality of life for the general population.
Treadmills are widely used in health and fitness facilities as well as sports institutes. In nations where the weather is too extreme (e.g. too hot or too cold) outdoor/over-ground walking and/or running may limit training volume which ultimately leads to a decreased acceleration in improvement of physical fitness for competition. The question is whether treadmill walking gait fully replicates outdoor/ over-ground running as treadmill walking may negatively affect running patterns and gait leading to decreased performance during competition.
While it has been established that the energy cost of treadmill running is lower compared to outdoor running, one author (Jones, 1996) recommended an increase of 1% gradient for energy expenditures similar to outdoor running. This may however lead to further changes in running gait on a treadmill.
The purpose of this review is to recognize the differences between treadmill and outdoor running whether positive, negative or neutral. Another aspect reviewed is the ground reaction forces experienced by a walker, running either on a treadmill and outdoors. Two journal articles are reviewed and compared with hope of answering these questions.
Review of literature
Two papers titled Gender Differences in Joint Biomechanics During Walking (Kerrigan et al., 1998) and Comparison of Vertical Ground Reaction Forces During Over Ground & Treadmill Walking by White et al. 1998 was selected for review. This review is to compare the difference between the two studies under the roof of walking gait. The relevance of this review is to establish whether or not there is a difference in 1) male and female gait and 2) gait difference leading to change in ground reaction forces (GRF) between over ground and treadmill walking.
Gender Differences in Joint Biomechanics During Walking, Kerrigan et al., 1998
This study was on the effect of gender on specific joint biomechanics during walking and assumed that there were difference between male and females. They hypothesized that quantitative analysis would reveal the differences in kinetic and kinematic forces between male and female subjects. These authors studied a total of 99 subjects (49 female and 50 male) which proved to be sufficient for data collection in contrast to many other studies which studied one gender predominantly with insufficient subjects. The main objective of the study was to establish the difference in hip, knee and ankle biomechanics of male and female subjects during walking. They also intended to look for specific joint difference (kinetic and kinematic) between the two genders.
In the author’s literature review, it was reported that females have the same or slightly shorter stride length compared to males but tended to increase their cadence (frequency of steps) to compensate for speed. However, both genders were shown to have the same comfortable speed of walking with similar velocities. The author’s findings were similar to those previously found.
The author studied 9 parameters of gait between male and female subjects. They categorized their results with statistically significant difference (P < 27 =" 0.0019)" style="">
Discussion
Kinematic and kinetic differences between genders were observed by the authors. They measured a total of 27 parameters. It was found that females had greater peak hip flexion and less knee extension prior to initial contact in terms of kinematic parameters. Females also had greater knee flexion moment in the pre-swing phase and greater peak knee absorption (kinetic parameters). These findings were all significant.
Other siginificant findings were that female had greater peak knee flexion, ankle plantar flexion, hip power generation in loading response, knee extension moment (at initial contact) and ankle power generation in pre-swing (0.00019 <0.05)>
Both male and female had very similar gait patterns with only 5 out of 27 significantly different parameters. The potential explaination for an increased hip flexion in females could be a result of a larger stride length in relation to height, which directly correlates with an increased use of hip flexors. The greater forces (kinetic) and increased kinematic paramaters are seen because of their increased in walking velocity (cadence x stride length) which generally requires more mechanical work to be performed. In a different paradigm, the increases kinetic and kinematic parameters can be caused by naturally higher forces generated by the limbs which naturally creates a higher cadence.
Comparison of vertical ground reaction forces during over ground and treadmill walking, White et al., 1998
Study by White at al. was to compare the difference of vertical ground reaction forces during over ground and treadmill walking. The authors studied 24 subjects who performed walks at 3 speeds categorized as slow, normal and fast. Before performing the study, the subjects were instructed to walk for 3-5 minutes on a 12-m walkway with an audio metronome to set a ‘natural’ cadence for accurate placement of foot on a piezoelectric force plate. The subjects were not aware of the placement of the force plate which was hidden under the floor to ensure no adjustment in stride length when walking was made. This proves to be a good method in setting the walking pace for the subjects. The authors recorded 6 successful over ground walking trails at each walking speed (slow, normal, and fast). Every treadmill walking trials were recorded with a video camera set perpendicular to the sagital plane. Vertical ground reaction forces (GRFv) was monitored and recorded using two piezoelectric force plates. These force plates were placed under the treadmill belt and made flat to the upper surface of the treadmill. Each step taken by the subjects (determining the speed) is given cue by an audible metronome (e.g. 20 beats per minute on a metronome was set for slow speed).
Vertical ground reaction forces measured was over a 30s data collection interval for each speed (slow, normal and fast). The measures included; 1) peak force during weight accepted, 2) minimum force in mid-stance, force peak in the last half of stance and the time from initial foot contact to each of the peak forces. Force magnitudes were also determined.
Other measures include cadence (steps per minute), stride length (horizontal distance from initial foot contact to next foot contact of the ipsilateral foot and walking speed were determined by video records for the over ground trials.
The finalized vertical ground reaction force data was collected and averaged over 5 over ground contacts for left and right foot. Force magnitudes were determined in Newtons (N). White et al. found that on average, no significance was found on cadence, walking speed and stride length between the two modes of walking although cadence and walking speed were slightly higher for the treadmill trials. Patterns of vertical ground reaction forces appeared similar between over ground and treadmill trials. Correlation was reported to be 0.998, 0.983 and 0.983 for the slow, normal and fast walking speeds respectively.
Findings that were significant in this study include force magnitude during mid and late stance during normal and fast walking speed while mid stance force was higher in normal and fast treadmill walking trials. However, peak force through late stance was lower for normal and fast walking speeds in treadmill walking. The higher force recorded during the mid-stance in treadmill walking during this study was initially thought to be because of a slower walking speed and shorter stride length. This theory however is not applicable to this study as walking speeds were equal. One study by Nelson et al. suggested that the higher forces generated in mid-stance on a treadmill was because of variables in limb motion which tended to be altered when treadmill speed was constant. This is a result of a decreased acceleration-deceleration mechanism.
A relationship between walking speed and forces generated during the early and late stance phases was also established. A higher force generation during the early stance was recorded during a slower walking speed as opposed to faster walking speeds. This can be explained with the same acceleration-deceleration theory suggested by Nelson et al. where during walking, there is more deceleration of the subject and treadmill belt.
Conclusion
The main objective of these two studies is to determine the difference in gait between the 4 variables, namely male and female gender and also gait on over ground and treadmill walking.
The study by White et al.,1998 was very precise, covering explanations of all methods used. Some of the mathematics and calculations behind several aspects such as cadence, stride length and walking speed were also clearly explained. This is beneficial for individuals who are less knowledgeable in this specific area of biomechanics. Their findings are beneficial for practitioners who wish to apply treadmill walking for various populations (e.g. rehabilitative) on the treadmill.
The study by Kerrigan et al. 1998, in contrast lacked several fundamentals; in fact one page of the journal article was missing. This paper however proved to show some significant results regarding gender differences in kinetic and kinematic parameters during walking gait.
References
Jones, A. M. (1996). A 1% treadmill grade most accurately reflects energetic cost of outdoor running. Journal of Sports Sciences, 14(4), 321-327.
Kerrigan, D.C., Todd, M.K (1998). Gender Differences in Joint Biomechanics During Walking: A Normative Study in Young Adults. Am J Phys Med Rehabil, 77, 2-7.
White, S.C., Yack, H.J. (1998). Comparison of vertical ground reaction forces during overground and treadmill walking. Medicine & Science in Sports & Exercise, 30(10), 1537-1542
http://en.wikipedia.org/wiki/Gait (human)
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