In a comment on my post about six weeks ago, Rick provided a link to an intriguing video recording by Somax. It raises the critical and controversial issue of the value of flexibility. Twenty years ago, few athletes questioned the orthodox belief that flexibility was a virtue; stretching was the accepted method of achieving the desired flexibility. However many studies have undermined the faith in the virtue of flexibility and stretching. On the other hand, there is good evidence that too much flexibility impairs performance. Relatively stiff muscles like stiff springs, capture and release of elastic energy more efficiently, than floppy muscles. Furthermore, several studies have shown that stretching does not reduce injury. This evidence has led many athletes and coaches to reject static stretching during warm-up and to propose that such stretching is more beneficial down during cool-down, though there are few studies that provide a clear demonstration that this is the case.
But before addressing this question in greater detail, it is worthwhile to step back and consider the overall credibility of the Somax video. It has been produced very professionally with informative picture of many elite athletes. It includes a great deal of thought provoking information about the features of efficient running. However it also makes sensational statements that appear to me quite misleading. The video quite rightly points out that getting airborne consumes energy, but claims that runners whose centre of gravity rises 4 inches and falls 4 inches on each step effectively run an extra two miles upward and two miles downwards during a marathon. This is a bizarre claim. It appears to assume that the COG moves horizontally for half the length of each stride and then moves vertically upwards 4 inches, as if tracing out two sides of a right angle triangle during each half stride. In fact the COG follows a curved trajectory that is only slightly longer than the shortest possible distance from its low point to its high point on each stride. The distance travelled by the COG is only marginally longer than the horizontal distance covered. In fact the COG follows a path that is only about 100m longer than the horizontal distance of the marathon. [Note added 16 Nov: actually the extra distance is nearer to 400m -as described in my reply to the comment by Jan.]
Furthermore, an appreciable fraction of the energy consumed in getting airborne is recovered in the form of re-useable elastic energy at footfall. In an article presented in the side bar of this page, I describe running as a dance with the devil. The devil (gravity) does extract a price but we too gain from the bargain. Getting airborne allows us to increase stride length and hence speed, compared with walking at a similar cadence. The video’s sensational description of the cost of getting airborne makes me wary of other material in the video. Nonetheless there are some thought provoking claims. Among these is the claim that increasing passive range of motion at the joints of the leg leads to an increase in speed.
Passive range of motion and distance running
I am very sceptical that passive range of motion is in itself relevant for distance runners. The normal gait of a distance runner does not involve forcing the joints of the leg near to the limit of their range of passive motion. In a runner with an apparently restricted short stride, the range of motion achievable during passive movement of the hip by an examiner is usually much greater than the small dynamic range of motion exhibited when running. There is some evidence that the resistance against passive stretch in the middle of the range of motion is correlated with passive range of motion, and it might be argued that enhancing the range of passive motion by stretching would be expected to decrease resistance to passive stretch in the midrange of motion. However, I remain to be convinced that decreasing resistance to passive stretch in itself is likely to increase speed. Many of the important leg muscle actions during running entail eccentric contraction – in which the muscle is passively stretched during active contraction. Therefore, during running, much of the resistance to free joint motion arises from active contraction of muscles, rather than static inflexibility.
However, this is not the whole story. It is also important to consider the orientation of the fibres that contribute to muscle stiffness. It is almost certain that the main reason runners develop stiff muscles is that the eccentric contractions that occur during running produce small-scale tearing of the muscle fibres. This results in a local inflammatory response that promotes the development of fibrous scar tissue. If these fibres are oriented along the direction of the muscles, they would be expected to do relatively little harm as they would increase the stiffness of the muscle in a way that would increase the muscle’s capacity to minimise damage during eccentric contraction. However any fibres that are oriented across the line of pull of the muscle will be harmful. They will create unhelpful resistance to contraction and furthermore might be expected to increase the risk of large-scale tearing of the contracting muscle.
Therefore it would appear very worthwhile to employ strategies to minimise the formation of these cross-bridging fibres during recovery, and to gently disrupt any such fibres that have formed following a previous session, during warm-up for the next run. It might be that passive stretching can help achieve this, but only if done in a gentle manner that minimises risk of destructive tearing of the muscle. Above all, the important thing is to apply the stretch in a manner that removes cross-bridging fibres that interfere with the pattern of muscle activity during running. It therefore seems to me that the one of the most appropriate strategies might simply be performing the action of running, but in a gentle manner. Thus the most important part of the warm up is simply running itself, starting at a very gentle pace and gradually building up to a pace near to the anticipated training or racing pace. This of course is what many runners do.
Gentle running during the warm-up might remove the potentially damaging cross-bridging fibres. What can be done to prevent these fibres forming in the first place? I think that this is one of the major roles of the recovery run. The formation of the scar fibres occurs over a time scale of about 24-48 hours after the initial trauma. It is likely that short-duration easy-paced running during this period will discourage the cross-bridging fibres while perhaps encouraging the formation of fires oriented along the line of pull of the muscle.
As an elderly runner, with reduced resilience in my muscles, I am concerned that even during easy paced running, the eccentric contraction might continue to do damage, so I therefore make sure the recovery runs are very gentle. Furthermore, because I have access to an elliptical cross trainer, I sometimes substitute a session of the elliptical in place of a recovery run. When the resistance of the elliptical cross trainer is set to a low level, the leg movements closely mimic the movements of running, but there is no impact and therefore minimal risk of damage from eccentric contraction. I cannot offer any substantial scientific evidence to support the value of this practice. However, the fact that during the past few weeks I have been able to increase my long run distance rapidly without any evidence whatsoever of muscle stiffness, and only occasional clunky feelings in my joints, is encouraging.
As I have described several times in recent weeks, I have had a frustrating year due to illness and other misadventures. Between the beginning of May and the end of September, I had trained sporadically and in particular, had done only two longish runs (15 and 16 Km respectively). In the four weeks from 1st to 28th October I had scarcely run at all. However, my eagerness to run at least one half-marathon this year led me to send off my entry fee for the Keyworth Turkey Trot, scheduled for December 12th.
So I have set myself the task of getting fit enough to race a half marathon within a month and a half, starting from a rather fragile base. High on my list of priorities has building up long run distance as quickly as my muscles will allow me. I have had to jettison the usually rule of increasing consecutive long runs by no more than 10 percent. However even higher on the priority list is minimising the risk of yet further illness or injury. I have decided that my best strategy for increasing long run distance rapidly without injury is incorporating a high proportion of sessions devoted to promoting active recovery of my muscles.
In the past few weeks, I have done four longish runs (16 Km, 23 Km, 17 Km and 25.5 Km). I have followed each of these runs with an easy recovery run the next day, and either a yoga session or an elliptical session on the subsequent day. So far, my muscles have coped without any complaint.
In the remaining few weeks of my preparation I will place increasing emphasis on getting some speed into my legs. I plan to do two vigorous sessions each week (a progressive longish run of 15-17Km and either a hill session or an interval session) while continuing to include both a gentle recovery run and an elliptical session between any two vigorous sessions.
My total preparation will consist of about 6 longish runs; 6 sessions devoted to development of the aerobic fast twitch fibres that will help me get my pace up to an acceptable half-marathon pace; about 25 active recovery sessions (either very gentle running or elliptical sessions) and a few sessions of yoga and/or strength development. The yoga sessions will play only a very minor role but will be designed to improve passive flexibility of hip flexors and extensors, quads, hams and calf muscles in addition to promoting physical balance and mental focus. The strength development will be directed at core, gluteals, hams, quads and calf muscles, with the primary goal of protecting my vulnerable knee.
In this proposed program, active recovery in the form of easy paced running and elliptical sessions will play a much more prominent part than passive stretching because I think it likely that contraction of muscles in a way that mimics as closely as possible the action of running while minimising the trauma of intense running, is likely to be an effective way to minimise the build up of scar tissue orientated across the direction of pull of the muscle.
Overall, I will place greater emphasis on the quality of my recovery than on the quality of my vigorous sessions. While there is a natural inclination when planning a training program to devote more attention to the quality of the key active sessions than to the quality of recovery, there is little doubt that if I get to the starting line for the Turkey Trot in mid-December in reasonable condition, it will be a greater tribute to the quality of my active recovery sessions than to the quality of the demanding sessions.