How essential is the leg kick in freestyle swimming? Professor Gatta analyses it scientifically and explains which points of the leg kick should be targeted on in coaching.
In line with varied anthropologists as man emerged from the water onto dry land, he was pressured to alter the best way through which he moved and – regardless of being born immersed in his mom’s womb – his return to the water as a swimmer appears to be a lot trickier than you may suppose.
There are numerous rival theories concerning the occasions main us to imagine that man is an aquatic creature who moved to dry land and, in distinction, different theories claiming he’s utterly unsuitable to being within the water. Supporters of the primary principle deal with a variety of important occasions occurring when an individual enters the water, for instance, when the rise in stress as a consequence of immersion tends to squash us, blood flows to our most inner organs to forestall this from occurring (the blood-shift impact). Then there’s the slowing down of our heartbeat and selective distribution of oxygen to these components of the mind the place it’s most wanted once we merely place our face in a bowl of water (the diving-reflex), and the way can we fail to be amazed on the manner new-born infants spontaneously maintain their breath when immersed in water only a few moments after they’re born? In different phrases, there are many occasions that may inevitably amaze anyone curious sufficient to learn “Your inside fish” written by Neil Shubin, professor of anatomy at Chicago College, through which he informs us that numerous diseases are as a consequence of the truth that…. sadly, as we developed, we stopped being fish.
Alternatively, supporters of the opposing principle level to an equal variety of occasions specializing in the horrible relationship between our physique and water. For instance, if we begin by making a comparability between a person and the mammal greatest as swimming, then there’s completely no competitors: our motion is slowed down by an enormous quantity of resistance and we devour extra power than a tank in inner-city visitors. Swimming is the slowest type of human locomotion that exists. In a nutshell, our physique shouldn’t be hydrodynamic and our limbs are too lengthy and skinny to be environment friendly!
And so, shifting on from strolling to freestyle swimming, it’s apparent that our limbs should work in utterly reverse methods. After we stroll, our legs enable us to maneuver ahead and our arms swing in the wrong way to our legs or, within the phrases, in time with our opposing leg with a purpose to stability our stride and stop us from shedding stability. Within the water, it’s our arms that generate most motion offering roughly 85% of ahead drive and the legs merely served to “stability” our place, stopping the physique from rotating round its axis (Persyn, 1995) and stopping our legs from sinking closely “behind” us (Zamparo, 1996).
However leaving apart all of the intricacies of the evolutionary growth of those occasions, what swimming coaches are most occupied with is that 15% of ahead drive coming from the decrease limbs and, as a consequence of our wholesome “skilled obsessiveness”, we inevitably begin considering straightaway about methods to benefit from it and even enhance on it to win races.
Legs are a lot stronger than arms, however the restricted mobility of leg joints stop any helpful movement from being generated.
Swimming freestyle utilizing your legs solely generates numerous lactic acid (Meyer 1999) and makes use of up three quarters extra oxygen than swimmingly with simply your arms (Adrian 1966). So, utilizing your legs shouldn’t be very advantageous and really energy-consuming. It additionally appears to be arduous to coach your legs: Konstantaki (2007) has labored out that, amongst swimmers coaching the identical manner, these devoting 20% of coaching particularly to simply their legs had no “statistically important” efficiency features over 400 m freestyle.
We’ve got additionally studied this subject and revealed a scientific paper about it within the journal Sport Biomechanics (“Energy manufacturing of the decrease limbs in flutter-kick swimming” -11-2012).
On this article, we targeted on the share of ahead propulsion the legs present in a flat-out dash. The check underscoring this analysis concerned coaching 18 national-standard swimmers who first glided impassively by means of the water after which flutter-kicked at most depth over more and more lengthy distances, whereas measuring the resistance to ahead movement. The machine used for this function (Ben-Hur ApLap Roma) is fitted with an electrical motor pulling a nylon cable that the swimmer holds on to whereas being pulled alongside the whole size of a 25 m pool.
On common the legs present round 50 Newtons (roughly 5 kg) of ahead propulsion at speeds of round 1.26 m/s. Because the pace will increase, the pulling machine begins to work and it’s straightforward to calculate the contribution coming from the legs by finding out the delta ensuing from evaluating the resistance measured throughout exams with no leg kick and exams, on the identical pace, with most leg kick. The attention-grabbing truth ensuing from these exams is that the ahead drive offered by the legs decreases as pace will increase. This impact is because of the dynamics of motion. The legs’ ahead drive might be proven in a graph because the power appearing alongside the perpendicular from the again to the foot in the course of the down-beat motion.
Breaking down this consequence right into a parallelogram of forces, two parts catch the attention: a “raise” vector stopping the legs from sinking and a propulsive vector: “drag” with backwards thrust producing ahead movement. As pace will increase the down-beat motion is not vertical however tends to tackle an identical path to the raise vector, because of the swimmer’s ahead shift. This inevitably ends in a lower in thrust given by the operate: ηL = -48,16x+112,8, the place the ability given in Watts is a operate of the pace (x). This operate permits us to estimate that the legs not assist the swimmer transfer ahead at theoretical speeds of roughly 2.3 m/s or higher.
This implies that a very powerful factor for acquiring higher thrust from the decrease limbs shouldn’t be higher muscular energy however moderately a excessive degree of joint mobility for the plantar flexion of the ankle.
This joint has restricted flexibility, so it might appear that this human fin has regularly straightened over time to permit folks to face up and it’s unusual that we now need to re-bend it once more!!!
