Perhaps the most enigmatic of the trainable capacities required for distance running is efficiency: the ability to generate as much speed as possible from a given amount of energy. In endurance events, when the vast majority of energy is generated aerobically, it is the ability to extract as much speed as possible from a given rate of oxygen consumption. Somewhat confusingly, it is usually reported as oxygen consumption required for a given speed and quantified in units of ml/Kg/Km, though this is actually the inverse of efficiency. It is also referred to as economy and is sometimes reported as speed at VO2max. A proportional increase in speed at VO2max will result in a similar proportional increase in speed at sub-maximal rates of energy consumption.
The first focus in planning a training program is on increasing the ability to consume oxygen (VO2max) by increasing blood supply to muscles and increasing mitochondrial enzymes, but for well-trained athletes, the scope for improving VO2max is small. When generating energy at VO2 max, a substantial amount of metabolism is anaerobic and results in the build-up of lactic acid. Since accumulation of acid limits muscle power output, the second focus of endurance training is reducing lactic acid accumulation, either by increasing the ability to transport lactic acid out of muscle cells and metabolise it in other tissues, such as liver and heart, or by enhancing fat metabolism, which does not generate lactate. However there is limit to what can be achieved by improving the capacity to minimise lactic acid accumulation. Once VO2max has been maximised and the accumulation of lactic acid has been minimised, the focus of training must shift to efficiency.
As illustrated by Andrew Jones’ account of the physiological developments achieved by Paula Radcliffe in the decade prior to her phenomenal a marathon time of 2:15:25 in London in 2003, the crucial improvement was in efficiency. Paula’s VO2max remain approximately constant at around 70 ml/Kg/min over the decade, but her estimated pace at VO2max increased by 15%. Andrew Jones acknowledged that mechanism by which this increase in efficiency was achieved remains a mystery.
In my recent discussion of this issue, I distinguished between improvement in metabolic efficiency: the amount of work that can be achieved by muscle contraction per unit of energy consumed; and improvement in mechanical efficiency: the pace achieved for a given amount of work by the muscles. Metabolic efficiency is strongly dependent on the relationship between rate at which muscle fibres shorten during contraction and optimum shortening rate for the type of fibre involved. In general during endurance running, the required of rate of shortening is relatively low. Type 1 fibres are more efficient than type 2 fibres when the rate of contraction is slow. Therefore, one goal of training is increasing the proportion of work done by type 1 fibres. This is achieved by low intensity training. But the need for the powerful contraction provided by type 2 fibres cannot be completely neglected because of their role in achieving mechanical efficiency.
Maximising mechanical efficiency demands optimising the balance between the three major energy costs of running: getting airborne; overcoming braking and repositioning the swinging leg. The cost of getting airborne can be reduced by spending more time on the ground, but that inevitably increases braking cost. Braking cost can be reduced by increasing cadence, but the cost of repositioning the swing leg increases with cadence so there is a limit to cadence. So one cannot escape the need to get airborne – indeed getting airborne is what distinguishes running from walking. But getting airborne requires a powerful push against the ground. The force-plate data of Peter Weyand and colleagues indicates that a major determinant of running speed is the ability to exert a strong push to lift off from stance.
For many distance runners, but especially women and elderly men, I think that the most likely factor limiting mechanical efficiency is lack of ability to exert an adequate push. One of the striking features of Paula Radcliffe’s running in her heyday was her ability to get airborne. The interesting question is how she developed this ability. Following her disappointing performance in the 10,000m in Sydney in 2000, her physiotherapist, Gerard Hartmann identified her poor ability to generate the power required to step on and off a high box rapidly. He recommended a course of plyometrics and weight training. It is likely that this played a substantial part in her transformation from a leading athlete who was struggling to fulfil her potential into the greatest female marathoner the world has seen. But was it the plyometrics or the weight training that played the greater part?
I was reminded of this question last week when Charles Eugster set a new world record for the MV95 200m in London, with a time of 55.38 seconds. Like most people, my first reaction was ‘how amazing’ though I was not entirely surprised. He had done a very entertaining TED talk a few years ago, in which he presented an enchanting picture of a 93 year old with a very positive outlook on life, and a strong message about the virtues of weight training for the elderly. The story behind his MV95 200m record provokes some interesting speculations about how to improve the ability to get airborne.
Charles was the child of Swiss parents and had spent his childhood in London, before returning to Switzerland. He had become a dentist despite his parents wish that he become a doctor. One of his teachers at St Paul’s school had said: ‘Eugster, if I were to put your brain into a sparrow’s head, there would still be room for it to wobble’. He decided that he would be better advised to focus on learning about 32 teeth rather than all the organs of the body.
He had played sport all his life, and in a particular, rowed for his school, but in his eighties, decided that it was time to smarten up his body. In his TED talk, he says it was all due to vanity. He claimed his ambition is to impress sexy young girls of 70 on the beach. He had wanted to start on a six pack but his personal trainer, Sylvia Gattiker, former Swiss aerobics champion, said he needed to start with work on his glutes. She stands no slacking, encouraging him along the lines: ‘…. and breathe out, no, that’s groaning…. breathe out’.
Under Sylvia’s guidance he has developed a spectacular body. He has won numerous body building and strength awards. At 89 he became world 80+ Strenflex champion. Strenflex involves a set of exercises that are scored for form and number of repetitions in a given time. It is a test of strength, endurance and flexibility. About two years ago, he took up sprinting, and within less than a year, was British 100m and 200m Masters Athletics 90+ sprint champion. So his world 200m record last week was amazing but scarcely surprising.
It is nonetheless intriguing to examine his style.
He runs with a high cadence but shuffling gait. He does get airborne, but not for long. I suspect this is part because Sylvia’s coaching emphasized reaching forwards with the swing leg, but it is a style quite characteristic of the elderly. Ed Whitlock, who trained for his 2:54:45 marathon at age 71 by running up to 3 hours per day in a Toronto cemetery, deliberately cultivated as slow shuffle to protect his knees from the pounding during training, but during races, he is a delight to behold: He gets airborne in a manner reminiscent of Paula Radcliffe.
By virtue of his rapid cadence, Charles Eugster reduces both the costs of getting airborne and braking costs, but to my eye, he nonetheless incurs unnecessary braking costs. His cadence appears is to be near the practicable limit, and any further improvement in efficiency would require spending a smaller proportion of the gait cycle on stance. His energy cost would almost certainly be less if he got properly airborne, as younger sprinters do. Impressive as his 200m time of 55.38 seconds is, it is almost certainly limited by a loss of the power required to get airborne.
The elderly lose strength but even more noticeably, they lose power: the ability to exert force rapidly. It has been recognised for some years that the elderly can regain strength with remarkable effectiveness by lifting heavy weights. Charles has clearly been very successful in achieving this. It is noteworthy that in order to become a Strenflex champion, for which it is essential to be able to perform repetitions of various strength exercises rapidly, Charles must have retained some power. Nonetheless, it appears that in training he has placed his main focus on shifting quite heavy loads, which is not a very effective way of re-building power.
Building power by explosive contractions
There is a substantial body of evidence indicating that the most effective way to build power is to perform muscle contractions at the rate that maximises power. Power is the rate of doing work. Work is the product of force by distance, so power is the product of force generated by distance the load is moved divided by the time taken, or on other words, the product of force by speed of contraction. Speed of contraction increases as load decreases, and for young adults, peak power is typically generated at about 30% of the maximum force that can be generated: that is 30% of one repetition maximum (1RM). The elderly have less scope for increasing speed of contraction, and maximum power is usually generated at a somewhat great fraction of maximum load. Typically maximum power is generated at 60% of 1RM.
Because the risk of muscle damage is greatest during eccentric contraction when a muscle is stretched while under load, the safest way to build power is to perform the eccentric phase of the exercise slowly and then execute the concentric phase explosively with maximum possible speed. Encouragingly, several recent randomised controlled trials have demonstrated that high velocity power training is feasible, well tolerated, and is effective in increasing leg muscle power in the elderly. De Vos and colleagues randomly assigned 112 healthy older adults (aged 69 +/- 6 years) to explosive resistance training at one of three intensities (20%; 50%; or 80% of 1RM) for 3 sets of 8 rapid concentric contractions , for 8-12 weeks, or to a non-training control group. Peak power increased significantly by about 15% in all three groups doing the explosive exercises, compared with 3% in the control group. In comparison with the groups using 20% and 50% of 1RM, the group using 80% of 1RM exhibited a greater increase in strength and also a greater increase in muscle endurance (the number of repetitions that could be performed with a load of 90% of 1RM). It is also noteworthy that injuries were rare and relatively minor during the explosive sessions. In fact there were more injuries during the testing of 1RM than during the explosive sessions, suggesting that explosive concentric contractions at moderate load are less risky that slow eccentric contractions at very high load.
Optimising the explosive contraction
The greater increase of strength at higher load reported by de Vos was expected, while the greater endurance at higher load when assessed at 90% 1RM might largely reflect a bias towards maximal recruitment of the type 2 fibres during the endurance test that were maximally recruited during the explosive training. However the similar gain in maximum power between the three different explosive training loads raises an interesting question about the possibility of biasing the training in favour of type 1 fibres. At low load, during the eccentric training phase, the type 1 fibres will be preferentially recruited and hence experience gentle pre-tensioning. During the explosive concentric contraction, it is likely that a wide-range of fibres would be recruited though the bias would usually be towards type 2 fibres. However, if the type 1 fibres have been pre-tensioned during the eccentric phase, these fibres will tend to show relatively more enhancement of recruitment. Thus, one might expect a somewhat greater benefit for type 1 fibres at low loads.
During the push off from stance during running (and during squats) much of the load is borne by the extensors of hip, knee and ankle. Most of the relevant muscles cross two joints, flexing one while extending the other, and hence the fibres undergo a relatively short contraction during the triple extension. Thus, even during quite fast running, the rate of contraction of the important muscles is relatively slow, and likely to be in the range where type 1 fibres are metabolically more efficient. This suggests that explosive training with low load might be potentially of greater benefit for endurance athletes.
With regard to the type of exercise most useful for runners, any exercise that produces a triple extension is likely to be beneficial. While deep squats do produce such an extension, the range of motion is different from that during running, whereas hang cleans require a range more similar to that of running. However, it is trickier to do hang cleans safely. It should also be noted that short, steep hill sprints and squat jumps are likely to be effective for increasing power.
The mechanism of the increase in power is not clear. It is likely that improved fibre recruitment due to enhanced neuromuscular coordination plays a role. If so, one might expect there to be a ceiling on the benefit that can be obtained over a prolonged period of training. Nonetheless, on the principle that using a muscle prevents atrophy, there are likely to be long term benefits in ensuring that muscles can be recruited with peak efficiency.
My preliminary experiments
During the past year, during which I have focused more on increasing volume of training than on either strength training or sprinting, I have been dismayed to find that my sprinting speed has decreased yet more than in previous years. Although I do not yet shuffle quite as noticeably as Charles Eugster (who is a little over a quarter century older than me) I too am forced to increase cadence to a very high level in order to produce speed.
About a year ago I had introduced plyometrics into my routine, but abandoned these as they appeared to be exacerbating the aches in my knees. I am therefore eager to find a safe way to increase leg muscle power. I have recently introduced sessions in which I do 3 sets of 8 explosive squats at 60% of 1RM. This has produced no DOMS and in fact leaves me feeling invigorated. I am even experimenting with doing 1 set of explosive squats at moderate load as part of my warm up for running sessions, with the expectation that this will enhance neuromuscular coordination.
It is too early to say whether or not this explosive resistance training has produced a worthwhile increase in ether sprinting speed or in efficiency at sub-maximal paces. Nonetheless, the impressive gain in strength achieved by Charles Eugster though training with heavy loads has somewhat paradoxically inspired me to try a different approach with the aim not only of increasing strength but also recovering the power to get properly airborne. But before I allow myself to become too dismissive of the approach employed by Charles Eugster, I should establish that I can run a 200m in 55 sec at age 75, let alone 95.