Cutting edge training for sport and healthy living
Who would have thought that the world record for the men’s 100m, would be an astonishing and awe inspiring 9.58 seconds? A time that by all measures should not have been possible until 2040 at least? The superlative Usain Bolt has raised the stakes, he has undoubtedly changed the scene of high performance athletics forever.
Faced with such astounding performances; where does the “average” coach or athlete go from here? Well it is fair to say that the answers or parts of the solution lies in the realms of science. Tacit knowledge or guess work may help; but surely science is the key to speed excellence?.
So; where do we go from here? Well, the science of running has moved on considerably from muscle fiber classifications and basic understanding of the strength qualities .
The Muscle-Tendon Complex
The work of Professor Mcneil Alexander and other researchers has elucidated the intricate and fascinating subject of locomotion. In particular, mammalian locomotion both biped (two limbs) and quad riped (four limbs) respectively. In order for mammals to run, gallop or sprint quickly and efficiently, a number of physiological, and bio mechanical processes must work optimally AND in unison. To move at great speed, it seems that the legs of mammals act as springs. They perform a series of bounces where gravitational energy is stored in a “retainer” on contact with the ground and released during the lengthening or push off phase. Human runners/sprinters are no different from other mammals. During locomotion, kinetic energy is transferred to potential energy. At lower speeds of running or when walking, the transfer is between kinetic and gravitational potential energy.
So where is potential energy stored?
Well the answer lies in the tendons of the limbs and aponeurosis or myofascial; tissue made of collagen and elastin that binds muscle together like glue. What is fascinating is how muscle interacts with tendons during mammalian and human locomotion. It has been held traditionally, that muscles lengthen or work eccentrically during the impact phase of running, and shorten or work concentrically during the propulsive or push off phase. On the contrary, new research seems to be almost heretic in its new findings. Muscle doesn’t contract eccentrically or concentrically on contact with the ground. If that is the case, then the final analysis leads to muscle working isometrically! This is in direct opposition to the commonly held belief that muscles need to be elastic during ground contact. Elasticity is needed yes, and both muscle and tendon are capable of storing energy in their elastic components , but tendons are far more efficient than muscle in this respect. The muscle-tendon complex relies on tendons acting as elastic entities and muscle acting as stiff components.
[caption id="attachment_495" align="aligncenter" width="300" caption="Gravitational and Elastic Actions in Walking and Running"]
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So why do muscle work isometrically during ground contact?
Before answering this question it is important to clarify the differing types of muscle contraction.
When force produced by a muscle exceeds the opposing forces of gravity, the muscle shortens, this is known as a concentric muscle action. When opposing forces of gravity exceed the forces produced by a muscle, eccentric muscle action occurs. When the force generated by a muscle equals the opposing forces of gravity, the muscle will contract isometrically.
Well the answer lies in the hill model and energetic efficiency. Hill (1938) showed that concentrically-contracting muscle uses more energy than isometrically-contracting muscle and this disadvantage is amplified as more force length changes occur. As the muscle is asked to generate more power concentrically (shortening) the cost increases, and so the need to use stored energy becomes greater (Blazevich).
According to the Hill model, a muscle fiber operating at intermediate shortening velocities can only produce a third of the force of the same muscle fiber contracting isometrically. So, in the case of high speed locomotion a muscle that operates isometrically will generate greater forces and hence lower ground contact times.
[caption id="attachment_496" align="aligncenter" width="300" caption="The three different types of muscle contractions"]
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Fewer muscle fibers are activated if muscle works isometrically, hence more energy is conserved. This is the secret of the fastest men and women in any running sport. Hark back to Bolt and his performances in the rounds of the 100m in the 2009 Athletics World Championships, he seemed to be jogging whilst his competitors were working frenetically to match his superior speed. This can be attributed to high isometric strength or muscle stiffness. As muscle fatigues and is forced to contract more eccentrically and concentrically; the more reliant the muscle becomes on glycolytic processes. Remember that the Hill model shows that energy cost increases as muscle contracts eccentrically or concentrically . If a muscle has the ability to express high levels of isometric tension then it will be able to do more work before it has to rely on a larger share of anaerobic gylcolysis.
[caption id="attachment_497" align="aligncenter" width="300" caption="Isometric contraction uses the least energy"]
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In a study by Locatelli(1996) where elite sprinters were tested to see whether there was a link between muscle stiffness, anaerobic glycolysis and high speed maintenance, it was discovered that elastic strength or muscle stiffness was a function of high speed maintenance. The ability to generate high levels of muscle stiffness of the tricep surea was linked to an ability to use anaerobic glycolysis as an energy source. In other words, the ability to generate top speed and maintain it relies on high levels of muscle stiffness and this muscle stiffness could only be maintained if anaerobic glycolysis can be utilised as an energy source. The study confirmed the well known fact that anaerobic alactic has a short time course of approximately 7-8 secs, and when the high energy phosphate system is spent, the body calls upon anaerobic glycolysis as the next level of energy utilisation to resynthesis the phosphate pool. In short, any sprint or run that is longer than 8 secs will call upon the lactacid system as an energy source to fuel muscle energetics. It must be pointed out that mammalian muscles utilise all their energy systems concurrently but one system will dominate depending on the length of activity.
In contrast to muscles, the economy of tendon function results from their lesser reliance on metabolic processes. Never the less, tendon cells have the ability to produce enzymes that use all three metabolic energy systems: the aerobic Krebs’ cycle, the anaerobic glycolysis, and the pentose phosphate shunt. As tendon cells mature, they rely less on the aerobic and more on the anaerobic pathways. Tendon reliance and a well-developed anaerobic energy production is essential if the tendon is to carry loads and remain in tension for periods of time. This dependence on anaerobic pathways (and in particular the glycolytic pathway); may explain why Locatelli et al found a link between anaerobic glycolysis, speed maintenance and muscle stiffness. It may be possible to improve the tendon qualities if training that utilises anaerobic glycolysis is coupled with stretch-shortening actions.
[caption id="attachment_500" align="aligncenter" width="300" caption="Athletes who are able to produce high amounts of energy from anaerobic glycolysis are more likely to achieve greater speeds."]
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[caption id="attachment_498" align="aligncenter" width="300" caption="If athletes are not able to produce energy from glycolysis then they won't be able to reach and achieve high speeds"]
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[caption id="attachment_504" align="aligncenter" width="300" caption="Stiffness is essential for maximum speed and speed maintenance"]
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Introduction
The ability to accelerate is an important quality to possess in sports such as Track athletics, Rugby, American Football, Soccer and Basketball.
The worlds fastest men (Usain Bolt, Asafa Powell, Tyson Gay), and women spend a large amount of their time training to hone this most important of skills. The ability to accelerate allows Rugby players like Brain Habana, Jason Robinson and Jos Lewsey to evade the opposition. In this post, we will analyse the mechanics and major muscles (also known as prime movers) fundamental to high performance acceleration. We will then suggest training methods to develop this most important quality for speedsters of all running sports.
Description of acceleration mechanics
At the start of a run or sprint, athletes have to assume a favourable position to accelerate their body. This position is characterised by a lean forward with the support or drive leg behind the body. An example is the start and acceleration position of the 100m in Track and Field. The acceleration mechanics can be characterised by a long stance phase and a floating phase that is short.
This position allows the athlete to apply more force and recruit muscle mass to overcome gravity.
Starting and acceleration differ enormously from constant speed or maximal speed. The foot spends a longer time (circa 180-250ms) on the ground and because of the lack of pre-stretch of the achilles tendon (relative to the constant speed phase) muscular strength is a significant factor for success. This type of strength is classified as explosive muscular strength. The foot is in a flatter position when making contact with the ground with very little rebound. Constant speed is characterised by a reactive action relying on the stretch-shortening of tendons, ligaments and muscles. The difference between the two phases of sprinting are the reasons why a sprinter can be world class at 60m yet an also run at 100m. Obviously the 100m requires a longer constant speed phase encompassing phases of maximal speed.
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Biomechanics
At the start, when the body is hanging forward, the back must be kept stiff and straight without any rounding, this is true for all acceleration patterns regardless of the sport in question. The lean can be achieved by bending the spine with a slight pelvic tilt (bending at the waist). Rounding of the back will weaken the role of the back muscles responsible for keeping the body and spine straight. The muscles responsible for this role are the erector spinae. A slight bend in the back at the waist allows the ES to participate in acceleration yet a rounding of the back diminishes the response. The ES is capable of rotating the pelvis and so can transfer energy through the pelvis, using the pelvis to aid the legs to apply force to the ground. The strength of the ES and latissmus dorsi is crucial in aiding an athlete to maintain the lean during acceleration. The stronger the dorsal and erector muscles the longer the athlete can hold the position and so prolong the acceleration phase. An often ignored but crucial area for success in acceleration is the development of upper body strength. Arm action can contribute to the force applied by a sprinter to the track. Fast explosive arm drive allows a stabilisation of the body but also takes advantage of the global workings of the central nervous system. As you move your arms explosively, the signals sent to the prime-movers also spill-over to the legs. The more forceful and explosive the arm drive, the more forceful and explosive will be the leg drive. Muscles of the shoulder complex and the upper back along with arm muscles contribute to stability and propulsion. The latissmus dorsi, trapezius, and deltoids are the prime movers in the arm drive, helping to mobilise the shoulder joint. Strong biceps and triceps will aid acceleration of the arms also. Quick mention should also be given to the neck. The neck has to be in line with the back, without bracing of the neck, the head alignment will cause acceleration to be less efficient. A neck brace used by boxers could come in useful for developing neck strength, this in particular will favour Rugby players in particular when they are tackled by the opposition, the neck will be able to react faster on impact to protect the spine.
[caption id="attachment_81" align="aligncenter" width="400" caption="Fig 2:The major muscles involved in acceleration"]
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Push-off can be strengthened by extending the ankle, knee and hip joint simultaneously; this is also known as triple extension. Hip and knee extension are compatible at stance phase and so the role of the rectus femoris is decisive in the acceleration phase. In short, the RM acts as a transmitter of energy between the two joints. The gluteaus maximus and quadriceps are the engines that generate force during the acceleration phase. The gluteaus maximus transmits its force to the knee through the ilio-tibial band and through the rectus femoris. The gastrocnemius transmits force from the knee to the ankle joint. The gastrocnemius acts very differently from the constant speed mechanics of sprinting, it has no rebound and so the muscle fibers in the gastro have to be able to provide the necessary forces.
During the acceleration the generation of force is the most important factor. A runner has to maintain stretch forcefully because a fast stretch wouldn’t allow enough time for application of muscular explosive strength. Thrust forces are more horizontally directed than running at constant speed. Inter-muscular co-ordination is very important. During acceleration, there is no pre-loading of hamstrings and outer pendulum swing of the leg. What takes place on the ground is decisive during acceleration and what takes place in the air is decisive at max speed. There is little landing energy to process during the stance phase of the acceleration and so greater force can be generated
The optimal angle for acceleration is 45 degrees but stronger athletes can manage more acute angles for the initial strides. Whether a sprinter, rugby player, soccer player or, the optimal angle of 45 degrees is the ideal but as the athlete becomes stronger, a more acute angle can be utilised.
Arm action should be vigorous and purposeful, with an emphasis on the shoulder joint. The head should be in line with the back, but in team sports, players need to see the opposition and team members and so it is not a hard and fast rule.
Exercises to develop the qualities of acceleration.
As mentioned earlier in this post, the acceleration is determined by the strength qualities of the prime movers and the angle of the body in relation to the ground.
To develop explosive muscular strength, there are many methods that can be utilised. Each can replace or compliment the other, but the most important quality to possess is high levels of maximal strength. There is no conflict between the possession of maximal strength and the acquisition of explosive strength. A higher level of muscular strength allows an athlete to readily obtain explosive strength. Below, you will find a range of possible methods for developing acceleration mechanics and strength.
Resistance training
Resistance training is the most popular means of obtaining strength and power in modern sports training. Resistance training can be used to develop maximal strength efficiently. A Load of 80-100% is sufficient to develop maximal strength. Loads can be set serially with optimum recovery of 2-5 min’s. The longer recoveries are needed for heavier loads. Most experts espouse this percentage range as ideal for developing max strength but, the key to developing maximal strength is to use a LIMITED range of reps. Regardless of the percentage, 2-3 repetitions are more effective than 5-6 repetitions. This is not an uncommon practice amongst power lifters and Olympic weight lifters. Resistance training should be undertaken for both upper and lower body. In particular, the shoulder complex should be targeted. A sequence of body building>max strength>power>strength/power endurance should be followed with each phase lasting approximately 2-3 weeks.
10-60m sprints
Sprint runs done over 10 to 30m will improve acceleration over time. Technique must underpin these runs over the set distance. A technical model for acceleration must be emphasised. An example of a session might be 2x3x30m sprints with 2 min’s between rep’s and 5 min’s between sets. 60m sessions can consist of 3x3x60m with 3 min’s between runs and 6 min’s between sets.
Resistance training
Speed squats
Speed squats are deceptively taxing, but also fun as well. The aim is to complete a set amount of reps in the shortest time possible. This brings an element of direct feedback into play for the athlete. A bench that allows the lifter to assume a position where the top of the thighs are parallel with the ground is utilised to standardise the exercise. A set amount of rep’s for example 5 repetitions, could be chosen for the session. Consequently; every weight used onwards is completed with five repetitions. The time taken to complete each set is recorded. This allows the coach and trainees to monitor their progress session by session. As progress is made, a noticeable pattern will reveal itself. The time taken to complete a lighter load in say session 1 will be the time taken to complete a much heavier weight in session 10 for example.
Depth jumps
Depth jumps with or without a rebound can also be used to develop maximal strength. The tension experienced by the extensors of the legs can exceed 3x bodyweight. The optimal height for developing maximal strength is 0.75-1m. A rebound is not necessary for the higher boxes, here the athlete can jump and hold the landing position for approximately 3-4 sec’s. Sets of 6-8 rep’s, done continuously, with a set recovery of 5-7 min’s are ideal. Lower boxes should be used until the athlete feels ready to increase the height. All depth jumps should be done with a double foot take off and landing.
Box jump ups
Box jump ups are an expression of explosive concentric strength. They are the opposite of depth jumps, where the emphasis is on developing muscular eccentric strength upon landing. Box jumps positively influence concentric actions and recruitment of muscle. The aim of the exercise is to jump two-footed onto as high a box as possible. The world’s most explosive athletes, weight lifters are capable of jumping on 2m+ boxes.
Box jump-ups should be done in sets of 3-4 with 8-10 rep’s and a recovery of 5 min’s recovery.
Vibration training
Vibration training is a very new method of training. This type of training can be used to develop maximal, explosive and reactive strength. Gains are most noticeable when developing maximal strength. If done properly, vibration training can add 20-40kg onto a squat in a short space of time. An optimum frequency needs to be chosen for each athlete. An EMG machine is inbuilt into the best vibration platforms. Duration on a vibration platform can be anything from 30 sec’s-2 min’s.
Jump squats with barbell
Jump squats with a barbell of 30-50% of maximum can also be used to develop the explosive strength needed for quality acceleration in athletes. The athlete positions the barbell on their backs and completes a set of very intense and challenging jumps. Squat jumps should be done on a mat that absorbs the landing shock, protecting the spine from unnecessary trauma. No other exercise targets the quadriceps and gluteals so intensely in preparation for acceleration.
Sleigh and hill work.
Towing a sleigh is an effective method for developing strength and acceleration mechanics. The sleigh should be towed for 30m on a flat surface. To control the exercise, the maximum decrement in time should be 0.8 sec’s. For example if you are capable of running 3.8 sec’s for the 30m then when using a sleigh the time should be 4.6 sec’s. This will solve the problem of selecting the appropriate weight for the sleigh.
Hill work
Hill work is an excellent natural means of developing acceleration mechanics and strength. The steepness of a hill will help an athlete to get into the right position for acceleration. Hill work can be done incorrectly if the right instructions are not conveyed to the athlete. The aim of the exercise is to improve the extension of the ankle knee and hip simultaneously. The extension of all three joints is known as triple extension. In order to achieve this desired effect the athlete has to resist the urge to scurry up the hill. The correct technique is like a bound up the hill with a knee drive forward and a forward rotation of the hip concentrating on fully extending all joints on contact with the ground. The optimum gradient is no greater than 6%.
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Conclusion:
Acceleration involves the use of many muscle groups to work synergistically. Concentric and explosive muscular strength is the determining factor. Technique is essential for utilising any gains made from increases in power.
A range of training methods can be used to develop the qualities needed for a better acceleration pattern.
