The effects of sloped surfaces on locomotion: An electromyo graphic analysis
Teachers College, Columbia University, New York, New York, United States Journal of Biomechanics
(Impact Factor: 2.75).
02/2007; 40(6):1276-85. DOI: 10.1016/j.jbiomech.2006.05.023
Investigations using quadrupeds have suggested that the motor programs used for slope walking differ from that used for level walking. This idea has not yet been explored in humans. The aim of this study was to use electromyographic (EMG) signals obtained during level and slope walking to complement previously published joint angle and joint moment data in elucidating such control strategies. Nine healthy volunteers walked on an instrumented ramp at each of five grades (-39%, -15%, 0%, +15%, +39%). EMG activity was recorded unilaterally from eight lower limb muscles (gluteus maximus (GM), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF), semimembranosus (SM), soleus (Sol), medial gastrocnemius (MG), and tibialis anterior (TA)). The burst onset, duration, and mean activity were calculated for each burst in every trial. The burst characteristics were then averaged within each grade and subject and submitted to repeated measures ANOVAs to assess the effect of grade (alpha=0.05, a priori). Power production increased during upslope walking, as did the mean activity and burst durations of most muscles. In this case, the changes in muscle activity patterns were not predictable based on the changes in joint moments because of the activation of biarticular muscles as antagonists. During downslope walking power absorption increased, as did knee extensor activity (mean and duration) and the duration of the ankle plantarflexor activity. The changes in muscle activity during this task were directly related to the changes in joint moments. Collectively these data suggest that the nervous system uses different control strategies to successfully locomote on slopes, and that joint power requirements are an important factor in determining these control strategies.
Available from: Dhurjati Majumdar
- "They reported muscle strains in 8.6% of the soldiers, 6.3% were diagnosed with ankle sprains, 5.9% had knee injuries and 3.0% suffered from stress fractures. However, only few studies have been reported regarding the muscle activations during uphill walking and the muscle recruitment strategies employed (Tokuhiro, Nagashima, and Takechi 1985; Arendt-Nielsen et al. 1991; Lay et al. 2007). Most of these studies are conducted at a self-selected walking speed. "
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ABSTRACT: Indian soldiers, while guarding the mountainous border areas, often carry loads in steep uphill gradients. This activity may predispose the risk of muscle injury. The present study aimed to examine the effects of an increasing load, speed and gradient during incremental uphill treadmill walking on different muscles. Twelve infantry soldiers walked on a treadmill at two speeds (2.5kmhr(-1) and 4kmhr(-1)) with no load, and carrying 10.7kg, 17kg and 21.4kg loads at 0%, 5%, 10%, 15%, 20%, 25% gradients. Electromyographic responses of Erector spinae (>240%) and Vastus medialis (>240%) were mostly affected, followed by Soleus (>125%) and Gastrocnemius medialis (>100%) at maximum speed, load and gradient combination compared to 0% gradient. Carrying 10.7kg at 15% gradient and above was found to be highly strenuous and fatiguing with the risk of muscle injury. Uphill load carriage in slower speed is recommended for the maintenance of combat fitness of the individual at higher gradients. Practitioner Summary The present article has evaluated the stress encountered by soldiers during load carriage at incremental uphill gradients while walking at different speeds by recording the muscular activities. Load carriage in steep uphill gradients is highly strenuous and may lead to muscle injury thus compromising the combat fitness.
Available from: Samuel Galle
- "After a standing rest condition (4 min), subjects performed a habituation (24 min) during level walking with a powered exoskeleton  at a treadmill speed of 1.36 AE 0.02 m s À1 . An uphill walking habituation would have induced fatigue and as uphill walking seems to be controlled by a modification of the level walking motor programme , we assumed that this would not influence the differences between the following uphill walking conditions. Subjects performed five randomized uphill conditions (4 min) at the same speed on a 15% inclination with 3 min of rest after every condition: one unpowered condition in which subjects walked with the exoskeleton without actuation of the pneumatic muscles and four powered conditions. "
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ABSTRACT: While level walking with a pneumatic ankle-foot exoskeleton is studied extensively, less is known on uphill walking. The goals of this study were to get a better understanding of the biomechanical adaptations and the influence of actuation timing on metabolic cost during uphill walking with a plantarflexion assisting exoskeleton.
Seven female subjects walked on a treadmill with 15% inclination at 1.36 m/s in 5 conditions (4 min): 1 condition with an unpowered exoskeleton and 4 with a powered exoskeleton with onset of pneumatic muscle actuation at 19, 26, 34 and 41% of stride.
During uphill walking the metabolic cost was more than 10% lower for all powered conditions compared to the unpowered condition. When actuation onset is in between 26 and 34% of the stride, metabolic cost is suggested to be minimal. While it was expected that exoskeleton assistance would reduce muscular activity of the plantarflexors during push-off, subjects used the additional power to raise the body centre of mass in the beginning of each step to a higher point compared to unpowered walking. This reduced the muscular activity in the m. vastus lateralis and the m. biceps femoris as less effort was necessary to reach the highest body centre of mass position in the single support phase.
In conclusion, subjects can use plantarflexion assistance during the push-off to reduce muscular activity in more proximal joints in order to minimize energy cost during uphill locomotion. Kinetic data seem necessary to fully understand this mechanism, which highlights the complexity of human-exoskeleton interaction.
Available from: PubMed Central
- "As a result, these patients tend to move their center of gravity toward their unaffected
side due to their fear of falling, and they become passive in rehabilitation training due to
these limitations and fears5,6,7,8,9). In particular, although
obstacle crossing requires larger movements of the hip joint because the body needs to be
moved not just horizontally, but also vertically, hemiplegic patients are limited in their
hip joint movements10, 11). However, underwater training can not only reduce the fear
of falling because it is safer than training on the ground and can be performed without any
impact or injury while providing physical stability with buoyancy and fluid resistance but
can also provide psychological stability so that patients can try it with confidence. "
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ABSTRACT: [Purpose] The purpose of this study was to examine range of motion (ROM) and the muscle activity of stroke patients during obstacle task on the ground and underwater. [Subjects] The subjects of this study were seven stroke patients in a hospital located in Daejeon, South Korea. [Methods] The measurements in this study were conducted in an exercise therapy room and a pool dedicated to underwater exercise (water temperature 33.5 °C, air temperature 27 °C) in the hospital building. The pool's water depth was determined by considering the levels of the xiphoid process of the study subjects. Ten-centimeter-high obstacles were used. An electrogoniometer was used to examine the ROM of flexion and extension of the hip joints on the affected side. An MP150 system a BioNomadix 2-channel wireless EMG transmitter was used to examine the muscle activity of the rectus femoris and biceps femoris of the affected side. [Conclusion] The results suggest that the unaffected side was supported, that the affected side moved, and that the hip joint was bent more underwater than on the ground. The rectus femoris and bicpes femoris were activated significantly less underwater than on the ground in all sections.
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