Sprinting/Running

Accelerating performance -- How athletes can make a quick getaway!

Acceleration is crucial to peak performance across numerous sports. John Shepherd analyses what makes for a quick getaway from a technical point of view and identifies the best training methods to develop this crucial aspect of sport performance.

Forget top speed, athletes that can increase their speed (i.e. accelerate) more rapidly than their rivals can gain an incredible and often matchless performance advantage. The most obvious example is the 100m sprinter who might not attain the highest top speed, but reaches the finish line first because he or she is able to attain their top speed before the other competitors. The same is true in racket and field sports; soccer and football players may breach the defense with a searing burst of pace that leaves the opposition for dead, while a racket sport player may accelerate to retrieve a shot that his opponent 'thought' was a winner.

Fast-twitch fibers, also known as 'white' or 'type II' fibers, contract two to three times faster than their slow-twitch counterparts, producing 30-70 twitches per second, compared with 10-30 for slow-twitch. There are two basic types of fast-twitch fibers:

Type IIa, aka 'intermediate' fast-twitch fibers or 'fast oxidative glycolytic' (FOG) fibers because of their ability to display, when exposed to the relevant training stimuli, a relatively high capacity to contract under conditions of aerobic or anaerobic energy production;

Type IIb fibers, the 'turbo-chargers' in our muscles, which swing into action for a high performance boost when needed. These are also known as 'fast glycogenolytic' (FG) fibers, since they rely almost exclusively on the short-term alactic/glycolytic energy system to fire them up. Slow-twitch fibers, aka type I, red or slow oxidative fibers, are designed to sustain slow but long-lived muscular contractions and are able to function for long periods on aerobic energy.

Most coaches and athletes will be familiar with type IIa and type IIb fast-twitch fibers, but it should be noted that other types have been identified. Former national athletics coach Frank Dick has described a further seven sub-divisions, although the differences between these are not considered significant enough for them to have a crucial effect on sports conditioning.(1)

Fast-twitch fibers are thicker than slow ones and it is the former that grow in size (hypertrophy) when activated by the 'right' training.

Activating fast-twitch motor units is the key to improved strength, speed and power. Unlike slow-twitch motor units, which are responsible for most of our day-to-day muscular activity, fasttwitch units are quite lazy and tend to slumber until called to action.

Fast-twitch muscle fiber is recruited synchronously -- i.e., all at the same time -- within its motor unit. This is, in part, a physiological manifestation of a neural activity -- sports skill learning. Let's use sprinting to explain this. Carl Lewis had a wonderful silky sprint action. His finely-honed technique, allowed his fast-twitch motor units to fire synchronously and apply power. The end result was championship and world record-breaking form. In short, Lewis' neural mastery of sprinting form allowed his fast-twitch motor units to fire off smoothly, operating like cogs in a well-oiled machine. It also allowed him to recruit the largest, and therefore most efficient, power-producing units. This latter ability is a further key element in developing optimum fast-twitch motor unit power.

By contrast, slow-twitch muscle motor units are recruited asynchronously, with some resting and others firing when carrying out endurance activity. Fast-twitch motor units are recruited according to the 'size principle', in that the more power, speed or strength an activity requires, the larger the units called in to supply the effort. It would, however, take a flat-out sprint or a near personal best(PB) power clean to fully activate them. This means that power athletes have to be in the right frame of mind to get the most out of their fast-twitch motor units. There is no such thing as an easy flat-out sprinting session or power-lifting workout.

By contrast, the endurance runner could go for a 60-minute easy 'tick-over' effort and drift mentally away from the task while still giving his or her slow-twitch motor units a decent workout. It is often assumed that those blessed with great speed or strength are born with a higher percentage of fast-twitch muscle fibers, and that no amount of speed work (or neuronal stimulation) will turn a cart-horse into a race horse. But, in fact, fast-twitch fibers are fairly evenly distributed between the muscles of sedentary people, with most possessing 45-55% of both fast- and slow-twitch varieties.

Thus, few of us are inherently destined for any particular type of activity, and how we develop will depend mostly on two factors:

The way our sporting experiences are shaped at a relatively early age; and how we train our muscle fibers throughout our sporting careers.

Seen below are comparisons of fast-twitch muscle percentages in selected sports activities with those of sedentary individuals -- and a very speedy animal. Note the extremes of muscle fiber distribution. The right training will positively develop more of the fibers needed for either dynamic or endurance activity, although the cheetah may not be aware of this!

Subject: Fast-twitch muscle fiber (%) Sedentary 45-55; Distance runner 25; Middle distance runner 35; Sprinter 84.

Cheetah: 83% of the total fibers examined in the rear outer portion of the thigh (vastus lateralis) and nearly 61% of the gastrocnemius were fast-twitch.

Positive adaptation of motor unit changes in sprinters showed that positive adaptations of muscle to sprint training could be divided into:

Morphological adaptations, including changes in muscle fiber type and cross-sectional area -- i.e., the ability of fast-twitch muscle fibers to exert more power by increasing in number and/or size; and, metabolic adaptations to energy systems to create more speed -- e.g., a greater ability to complete short repeated maximal efforts, acquired through an improvement in the short-term alactic/glycolytic energy system which is, in turn, gained from the creation and replenishment of high-energy phosphates.

Conversely, the wrong training -- and even what might in some cases seem to be the 'right' training -- can compromise their development.

The best training methods for fast-twitch motor units are as follows:

Lifting Weights in Excess of 60% 1RM: The heavier the weight, the greater the number and size of fast-twitch motor units recruited. A weight in excess of 75% 1RM is required to recruit the largest units.

Performing a Physical Activity Flat-Out -- e.g., sprinting, swimming, rowing or cycling as fast as possible. Adequate recoveries are needed to maximize effort. The short-term anaerobic energy system will positively adapt. The minimum speed needed to contribute towards absolute speed development is 75% of maximum.

Training your Muscles Eccentrically: Research indicates that this form of training increases fast twitch motor unit recruitment.(6) An eccentric muscular contraction generates force when muscle fibers lengthen (see plyometric training, below)

Plyometric Training: These exercises utilize the stretch-reflex mechanism, allowing for much greater-than-normal force to be generated by pre-stretching a muscle (the eccentric contraction) before it contracts. A hop, bound or depth jump is an example of a plyometric conditioning drill; a long jump take-off is an example of a plyometric sport skill.

Complex Training: This can induce greater recruitment of fast-twitch motor units by lulling the protective mechanisms of a muscle into reduced activity, allowing it to generate greater force. Complex training involves combining weights exercises with plyometric ones in a systematic fashion (see PP 114, Feb 1999). A good example is: 1 set of 10 squats at 75% 1RM followed, after a 2-minute recovery, by 10 jump squats, repeated 3 times

Over-Speed Training: This will have a transferable neural effect only if the athlete consciously moves his own limbs at the increased pace. It includes downhill sprinting and hitting or throwing sports using lighter implements

Good Recovery: 24-48 hours; recovery should be taken between very intense plyometric/complex training and speed work sessions. A further 24-36 hours; recovery will result in an over-compensatory peak -- i.e., opportunity for a peak performance.

Sport Specific Warm-Up: This will reduce the risk of injury, increase the receptivity of the neuromuscular system to the ensuing work and reduce the potentially contradictory effects of non-specific preparation on fast-twitch motor units

Mental Preparation: Maximum fast-twitch motor unit recruitment can result from specific mental preparation before and during competition Let's return to the sprint training research of Ross and his team.(3) They believed that volume and/or frequency of sprint training beyond what is optimal for an individual can induce a shift towards slower muscle contractile characteristics. Basically, this means that if a sprinter were to perform too many under-speed track reps, his top speed would be impaired.

What's Best for Power Athletes? For 100% power athletes (such as 100m sprinters) and even those involved in sports where occasional maximal or near maximal quick flashes of power are required, such as golf, baseball (pitching and batting) and football (goal keeping), it may well be that high-intensity training sessions, interspersed with long periods of rest, are best for the optimum development of fast-twitch motor units, particularly in-season. This can make the conditioning process very difficult.

Although a general level of aerobic fitness is useful, it is possible that too much steady state work, particularly in-season, could blunt the atheletes#39;s sharpness and dull their fast-twitch motor units.

In-season it may be far better for them to condition themselves using sprints, medicine ball work and autogenic training (a form of mental conditioning). Think of the cheetah in our muscle fiber distribution comparison. What does this fastest land animal do? It lies around all day, exploding into action every now and again: fast-twitch fiber development heaven -- but hell for its prey!

In support of this point, Ross' team noted that detraining appeared to shift the contractile characteristics of fast-twitch motor units towards type IIb, thus providing them with more potential output. This effect can often be seen in power athletes who sustain minor injuries after a good period of training and are then obliged to train lightly for 2-3 weeks. Afterwards, to their complete surprise, they often produce a PB because the enforced rest has facilitated the fiber to shift and upped their fast-twitch potential. Other research has indicated that a decrease in weight training after a prolonged period of training can have a similar effect.(5) Note though, that too long a lay-off can produce less positive effects, due to muscle shrinkage (atrophy) in sports where muscle size is also important, eg., for shot putters and American football line-men.

Authored by John Shepherd

References: 1. Dick F Sports Training Principles (4th edition) A&C Black 2002 2. J Comp Physiol [B] 1997 Nov;167(8):527-35 3. Sports Med 2001;31(15):1063- 82 4. Sports Med 1990 Dec;10(6):365-89 5. Acta Physiologica Scandanavica, 151, 135-142 6. J of Strength and Conditioning Research vol 16 (1), 9-13

Specific Programs

BreakAway Speed offers the following programs designed to benefit sprinting / running athletes.

Speed Training

Our training philosophy is for the maximum development of speed and power through the use of functional movements. We incorporate a wide variety of training through ground based, multi-joint strength and speed exercises, Olympic lifting techniques to develop strength and power, flexibility, balance, agility, injury prevention (post-injury rehab), and sport-specific training. Session Times: M, W, F: 4:30pm, 5:30pm T, Th: 4:30pm