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The transmission efficiency of backward walking at different gradients
No full textThe specialized design of the bipedal system towards forward locomotion has been assessed by measuring the metabolic cost and the mechanical work of both forward and backward walking on a treadmill at seven gradients from 0 to +32%. With respect to forward locomotion, backward walking implies: (1) a higher metabolic cost particularly at level gradient, while at steeper inclines the difference decreases, (2) the same mechanical internal work despite an increased stride frequency, (3) higher mechanical external work within a gradient range from 0 to +15%, (4) lower "energy recovery", i.e. the ability to save mechanical energy by moving as an inverted pendulum, mainly in level walking, and (5) as a consequence of the above results, a decrease of the efficiency of locomotion particularly at the 0% gradient. The transmission efficiency of backward walking, relative to the forward progression, was found to be about 65% in level locomotion, while at higher gradients it increased to and was maintained at a value of about 93%. The poorer economy of level backward walking could also be explained by an impaired elastic contribution in the last part of the double contact phase, while the similarity of the two gaits on higher gradients is caused by disruption of the pendulum-like paradigm due to the trajectory geometry of the body's centre of mass progressively losing its downward portion
Letter to the Editor concerning "Is the 4 mm height of the vertebral artery groove really a limitation of C1 pedicle screw insertion?" (by Da-Geng Huang, Si-Min He, Jun-Wei Pan, et al. Eur Spine J, 2014, 23(5):1109-1114)
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Answer to the Letter to the Editor concerning "Is the 4 mm height of the vertebral artery groove really a limitation of C1 pedicle screw insertion" by Da-Geng Huang, et al. Eur Spine J (2014) 23(5):1109-1114. [Eur Spine J. 2014]
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Is the 4 mm height of the vertebral artery groove really a limitation of C1 pedicle screw insertion? [Eur Spine J. 2014
Signal or noise, a statistical perspective
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Reply to Padulo et al.: Jymmin, an easy-to-implement musical workout approach. [Proc Natl Acad Sci U S A. 2014]
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Musical agency reduces perceived exertion during strenuous physical performance. [Proc Natl Acad Sci U S A. 2013
Vertebral rotation in adolescent idiopathic scoliosis calculated by radiograph and back surface analysis-based methods: Correlation between the Raimondi method and rasterstereography. Eur Spine J;22:2336-2337 - Statistical perspectives part II
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Letter to the Editor concerning "vertebral rotation in adolescent idiopathic scoliosis calculated by radiograph and back surface analysis-based methods: Correlation between the Raimondi method and rasterstereography"
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Letter to the Editor concerning "Range of motion of thoracic spine in sagittal plane"
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Energetics and mechanics of human walking at oscillating speeds
No full textSYNOPSIS. Seven subjects walked on a programmable treadmill both at constant (3.5 ±0.0 and 5.0 ±0.0 km/hr) and oscillating speeds (±0.5, ±1.0, ±1.5, ±2.0 km hr~'), set to sinusoidally change between the two limits in 3 sec. In each condition oxygen consumption measurements were taken. The same experimental protocols were replicated on a walkway by asking subjects to adapt their stride frequency to an audio signal corresponding to the sinusoidal stride frequency changes measured on the treadmill. Differently from what expected, only the ±2.0 km hr~' oscillation resulted to be metabolically different from the constant speed walking, both for the treadmill and the walkway conditions. The time course of the mechanical energy of the body centre of mass could reveal that a strategy devoted to benefit from the usual energy fluctuations occurring at constant speed, is likely to be used to cope with speed varying sequences. From the energy curve observed at constant speed, it is possible to derive an energetically equivalent curve by cumulating acceleration portions, and deceleration ones, of a group of strides as to produce a single acceleration and a single deceleration phase, as it is observed in oscillating speed walking. Being aware of the bias introduced by using a non- , inertia! frame (the treadmill protocol), we are replicating the experiments with a laser beam projected on a wide radius circular path at oscillating speeds, that the subjects have to follow. The preliminary data seem to confirm the invariance of the metabolic requirements in oscillatory walking up to ±1.5 km hr~'
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