yogabook / movement physiology / bipedal locomotion
Bipedal locomotion
Cyclical forward movement on two legs to cover distances, consisting mainly of placing one leg (offset) in front of the other and covering the desired distance in the sum of the steps. The colloquial term „Walking roughly classifies the following activities:
Jogging, and not just running, has a number of positive physical effects: Increased endurance and cario-pulmonary performance, preventive effects against some important civilization diseases such as heart attack, ischaemic stroke, arteriosclerosis, vascular dementia, diabetes mellitus, a positive influence on bone density and supports weight reduction, after all, jogging burns between 700 and 800 kcal / h and thus a third of the needs of a quietly living person with office work. Running consumes (with an 80 kg test person and 15 km/h) around 1200 kcal/h, of which between 70% and 80% is released as waste heat via sweat, around 1-2 l / h. While the stride frequency for jogging is often between 140 and 170 / minute, the stride length is rather short compared to running, often not exceeding the stride length for walking and falling well short of the stride length for forced walking. A typical jogger places one foot no more than one to two foot length away from the other, i.e. has a stride length of no more than two foot lengths. In contrast, even less trained runners quickly reach stride lengths of well over one meter, with foot lengths of around 20 (shoe size 32) – 30 (shoe size 47) cm on average, this usually corresponds to more than three times the foot length. The world’s top sprinters have stride lengths of 2.50 m, which is more than eight times the length of their feet. Even top marathon runners still have stride lengths of 1.50 m, i.e. more than five times the length of the foot. Despite and precisely because of the short, frequent strides, jogging also has its downsides: The center of gravity curve has a greater curvature in jogging than in running, the vertical oscillation is – depending on the running pattern – usually somewhat more pronounced in relation to the stride length, especially in relation to the stride length this becomes very clear.
While in running, pushing the foot off the ground using the power of the triceps surae moves the body’s centre of gravity forwards – the aim is speed – the focus in jogging is shifted more upwards in the direction of the take-off movement due to the shorter stride length. This results in significantly less strengthening of the entire extensor area of the hip joint, but also of the hip flexors: with the same stride frequency, the hip joints have to be extended and flexed proportionally more and disproportionately more powerfully for a longer stride length. The latter is due to the fact that the legs have to be constantly accelerated and decelerated (i.e. negatively accelerated), and the time factor is in the denominator of the acceleration, i.e. it has a hyperbolic influence. Like the stride length, the stroke (the radian measure as well as the working range ot the triceps surae) in the ankle is significantly greater when running, so the rolling motion is much more pronounced. In relation to the strengthening effects, jogging therefore shows far more impact loads due to the more frequent impact of the foot. This is less favorable for all joints involved. Especially postpartum, this also becomes an important factor outside the musculoskeletal system when the pelvic floor muscles are still stretched and weak. Jogging should therefore only be started or resumed after some time of regular pelvic floor training and complete freedom from symptoms. The short stride length also results in far less stabilization work to be performed by the trunk muscles.
Since the pelvis oscillates around a transverse axis (a transverse horizontal line) during running, as well as around the longitudinal axis (a vertical line), and also oscillates around a sagittal plane, a significant part of the musculature, especially of the lower torso, must counteract this so that the torso has to follow the movements of the pelvis as little as possible, which would result in an immense loss of energy or speed and rapid fatigue. While walking on the one hand and jogging and running on the other can be clearly distinguished by the fact that at least one foot is always in contact with the ground when walking, this is not the case for jogging and running, where there is a flight phase. This also exists in the sharpest form of running, sprinting. It is difficult to make a clear distinction between jogging and running on the basis of objective parameters; the best way to do this is to look at stride length. In addition, jogging allows for comfortable and unlimited conversation, which is not the case with running, as having conversation significantly impairs the amortization of the higher oxygen debt and intensive breathing affects articulation. The distinction between running and sprinting is easy, since running is an aerobic discipline, i.e. no amount of oxygen debt is generated in the tissues that cannot be repaid in real time. Sprinting, on the other hand, is clearly an anaerobic discipline that can only be sustained for a few hundred meters at best. The center of gravity curve is quite smooth, so the height oscillation of the body’s center of gravity is low. Sprinting is always forefoot running, longer distances are almost always run with a rolling motion at least as midfoot running, usually and almost always at a hobbyist level as rearfoot running.
All 4 forms of movement (walking, jogging, running, sprinting) have in common that propulsion comes almost exclusively from the hip extensors and the triceps surae (and other less contributing ankle extensors). The proportion of the gluteus maximus as a force extensor of the hip joint will still be very small at low speeds, but will then predominate in sprinting. When walking in particular, you can vary greatly between the use of the triceps surae and the hamstrings, which normally contributes the most to propulsion. In principle, powerful use of the gluteus maximmus is possible when walking, but is not typical at moderate speeds. Differences lie in the point of contact of the foot or the body’s center of gravity: when running or sprinting faster, the foot must be placed approximately below the body’s center of gravity. A touchdown point that is too far in front of the center of gravity is uneconomical and promotes wear. Compared to running, sprinting increases not so much the stride length but above all the stride frequency, which also explains the dramatically increased energy requirement, as time, as already described, enters into the calculation hyperbolically. Even if some authors state a speed of 10 km/h as the approximate limit between jogging and running, this is highly individual. This becomes even clearer in running vs. sprinting. Top-class marathon runners can easily run at 18 km/h, which a much less trained runner often cannot even achieve in a sprint. In the same way, a speed of 7 – 8 km/h can easily be achieved when walking, whereas leisurely joggers may barely reach the walking speed of 5 km/h. In this case, the biggest difference lies in the stride length, which can be significantly longer in ambitious walking than in tripping jogging. The increase in stride length from walking to jogging to running (and hardly any more to sprinting) is also reflected in the ROM achieved in the respective joints. Objective time measurements or speeds are therefore of little use for differentiation.