Cross training

The past few days have not been kind to my lungs. My peak expiratory flow has fluctuated between 500 litres/min (fairly good) and 240 litres/min (a level at which even mild exercise causes me to wheeze). I am not sure why the situation has deteriorated, as the weather has been milder this week with air temperatures well above zero degrees C. Today I did 4x1Km aiming for mean heart rate 142. I found it more effortful than last week. I managed to keep the mean HR at 142.5, but my average time per Km was 4:24, compared with 4:21 last week, and 4:20 in early December before my current episode of respiratory problems began.

I have contemplated stopping training for a while, but I doubt that would help, as my respiratory problems usually tend to persist for months following a cold or flu. During my short-lived return to running in my late 50’s, I developed a cold and stopped running. I still had symptom three months later, and had lost most of my fitness. The current symptoms are mainly due to excessive reactivity of my airways to any irritation rather than persistent infection. Unless I develop clear signs of bronchitis, I will persist with light to moderate intensity training. At this stage I am undecided about the mile race next week. If there is no further deterioration I might run, but an M60 PB is unlikely.

Cross-training

Since the onset of my breathing problems I have been doing a moderate amount of indoor training on the elliptical cross-trainer to minimize exposure to the cold air that irritates my bronchioles. In a recent comment Ewen raised the question of whether or not low intensity running might be as beneficial as cross-training. As with most questions to do with the optimal way to train, the issue is debateable. Some of the relevant ‘facts’ are:

1) A previously fit runner who changes to a program of cross-training alone, will suffer a substantial deterioration in running performance.

2) A previously fit runner who adds cross-training to his/her current training program can achieve a worthwhile improvement in running performance.

3) High volume running produces short term damage to muscles which can promote improved performance after recovery.

4) High volume running can result in muscle damage which is more persistent than that due merely to over-training, and may be permanent, in at least some individuals.

Each of these ‘facts’ is supported by a substantial amount of scientific and anecdotal evidence, but I do not have time to address all of these issues today. Maybe in future posts I will look at the evidence for each of these statements in some detail. Today I want to address several speculative issues that are relevant to Ewen’s comment:

1) In races run at paces in the vicinity of lactate threshold pace (10K to marathon) the ability to remove lactate from the blood stream is as important as the minimization of lactate production.

2) Elliptical cross training (and cycling) might be more effective than low intensity running in engaging fast twitch fibres (which tend to work anaerobically and therefore produce more lactate) but does less damage to muscle than is typical of high intensity running. Therefore, elliptical cross-training might be a safer way to develop the capacity to remove lactate from the blood stream.

Increased removal v reduced production of lactate

A study by Tim Noakes and colleagues from Cape Town demonstrated that lower blood lactate values during exercise after training were due to diminished lactate production at low work rates but in contrast, were due to elevated removal of lactate higher work rates, (McRae et al, Effects of training on lactate production and removal during progressive exercise in humans, Journal of Applied Physiology, Vol 72, 1649-1656, 1992). Thus, when running at paces near or above lactate threshold, the ability to remove lactate appears at least as important as the ability to minimize production of lactate.

Engagement of fast twitch fibres during concentric contraction

Resistance training typically engages fast twitch fibres resulting in muscle hypertrophy, whereas high volume low intensity running engages slow twitch fibres resulting in improved endurance, but minimal hypertrophy. This is dramatically illustrated by the identical twins, Otto and Ewert, described by Mike Rennie in the GL Brown Prize Lecture on Physiology in 2005 (Rennie, M., Exp. Physiol vol 90 pp 427-436). Otto trained for endurance events and developed a lithe, endurance runner’s physique, Ewert trained for field events and developed the ‘walnuts in a stocking’ look that Arnold Schwarzenegger subsequently emulated. Depending on taste you might find Otto a little puny. (See http://www.arthurdevany.com/webstuff/images/Twins.tiff)

In examining the effects of resistance training on different muscle fibre types, it is important to take account of the differences between concentric contraction, in which the muscle shortens as it develops tension, and eccentric contraction, in which the muscle is required to develop tension while it is being stretched.  A study of the effects of a resistance training program involving eccentric and concentric muscle contractions compared with concentric contraction alone, conducted in Gary Dudley’s lab, demonstrated that the combined eccentric/concentric program produced hypertrophy of both fast twitch and slow twitch fibres, whereas the program that included only concentric contraction (but similar total workload) produced mainly hypertrophy of fast twitch fibres. (Hather et al, Acta Physiologica Scandinavica, Vol 143 , Pp 177 – 185, 1991). Thus, for maximal development of muscles fibres during resistance training, it is necessary to combine eccentric with concentric contraction.

It is also of interest to note that concentric training produced an increase in capillaries per fibre area for both fast and slow twitch fibres and that the increases in capillaries were maintained 4 weeks after discontinuation of training.

Differences between running and elliptical training

It is necessary to be cautious in applying any conclusions from a study of resistance training to either running or elliptical training. Nonetheless, it is noteworthy that running and elliptical training differ in the relative amounts of eccentric and concentric contraction. Running involves relatively more eccentric contraction. In the quadriceps, the majority of the work while running is eccentric contraction performed as the muscle is stretched at footfall. In contrast, elliptical cross-training involves a more sustained concentric push by quadriceps. Thus elliptical training would be expected to engage fast twitch fibres to a greater extent. This is consistent the observation that ventilatory threshold (and therefore, the lactate threshold) occurs at a lower heart rate and lower level of energy consumption on the elliptical. This implies a higher proportion of anaerobic contraction, which is characteristic of fast twitch fibres.

So elliptical training (and also cycling) apparently differs from running by relatively greater engagement of fast twitch fibres and greater lactate production at a given level of energy consumption. Elliptical training might therefore be useful for developing the ability to metabolise lactate. Is this likely to be a beneficial form of training for a runner? At first sight it appears to be a waste of time for a distance runner to miss an opportunity to employ eccentric muscle contractions which might be used to develop both slow and fast twitch fibres. It should be noted that, contrary to the teachings of Hadd, even at running paces that engage predominantly fast twitch fibres there is also at least some development of slow twitch fibres – (see Dudley et al. Influence of Exercise Intensity and Duration on Biochemical Adaptations in Skeletal Muscle,’ Journal of Applied Physiology, vol. 53, pp. 844-850, 1982). But running at paces fast enough to induce the enzymes that metabolize lactate is where the issue of muscle damage enters the equation.

I can do elliptical sessions including about 30 minutes at the ventilatory threshold on four consecutive days without noticeable muscle stiffness or pain, whereas two consecutive days of running at ventilatory threshold pace for 30 minutes leave me a bit stiff and sore – yet I have spent far more hours running than training on the elliptical and would therefore expect to be relatively better adapted to running.

In conclusion, the elliptical appears to offer the prospect of inducing production of the enzymes that metabolize lactate with minimal wear and tear on the muscles. This is a tentative conclusion based on a slender evidence base, and I will not be convinced that it will lead to more effective training until I have more experience of putting it into practice. Nonetheless, I think the evidence is good enough to justify a trial of mixing running and elliptical sessions.

So for the time being, I will continue with both running and elliptical sessions. The running will include low intensity sessions and a small number of moderate intensity sessions. The low intensity running sessions are designed to increase mitochondria in slow twitch fibres thereby decreasing lactate production, while also increasing ability to metabolise fat and strengthening connective tissues. The moderate intensity running sessions are designed to increase mitochondria in both slow and fast twitch fibres producing not only a decreased rate of lactate production but also increasing the ability to metabolise lactate. The elliptical sessions will be mainly of moderate to high intensity, with the goal of increasing the ability to metabolise lactate and also increasing capillaries per fibre, but with minimal risk of muscle damage. Thus each type of session has its own major goals. There is of course the risk that mixing the various types of sessions will be counter-productive, but that is another complex issue that will have to be deferred to another day.

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One Response to “Cross training”

  1. Ewen Says:

    Thanks again Canute. It’s interesting to read about the different effects of eccentric and concentric muscle contraction. I hope your health improves soon so you can come to a conclusion about the elliptic trainer.

    Regarding your comment about innovation as one gets older… that is so true. I’m a great believer in maintaining the speed side of training – the elliptical could be a way of doing it without the risk of injury from certain drills and hill sprints.

    I’m going to try and include a session of a small number of near maximal 100-200m sprints with full recovery. I’ve noticed that these do work the quads. Do you think downhill sprints or strides (on a gentle slope) would be useful?

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