Atrophy of fast-twitch aerobic muscle fibres

In last week’s Keyworth Turkey Trot half marathon I failed to achieve my optimistic target time of 105:30 though I was not surprised, as my paces in training, especially during interval sessions, suggested that 110 minutes would have been a more reasonable target. It was a hilly course and it was the hills that were my undoing. I mostly maintained a pace around 4:40 to 4:50 min/Km on the level sections and the down-slopes, but sometimes slowed to paces even slower than 7 min/Km on the more substantial hill climbs.  As it turned out I was quite evenly matched overall with a young woman named Emily, but there was a marked difference in our strengths and weaknesses. As described in my race report last Sunday, I simply could not match her pace on the uphill stretches.

Although my aerobic capacity is still below where it was a year ago, my lack of speed in training and my inability to sustain a reasonable pace on the hills during the race  points to the major problem being inadequate strength of my type 2a aerobic fast twitch fibres.  This is not unexpected.  Since February I had been dogged by inflammatory arthritis and its aftermath.   The inflammation had affected several joints, especially my left knee.  This was the first time in the fifty years during which I have suffered these episodes of arthritis that my left knee has borne the full brunt of the attack.  In the past, my right knee has suffered more, and as a result, my right leg has been weaker than my left for many years, despite the fact that I am right-footed.

The pain in my left knee that had still been lingering in October had diminished further throughout the six weeks of training in preparation for the Turkey Trot.  During the race itself, there was no hint of discomfort in my knee, and there have been only a few very minor twinges since.  So today I decided it was probably safe to attempt the hopping test that I have used in the past to assess leg strength.  In this test, I measure the distance covered in a series of 5 hops on one leg.

In mid-December 2009, six weeks into the systematic training program that I had embarked upon at the beginning of November that year, the distance covered in 5 hops on my left leg was 9.71 metres, while I  covered 9.24 metres in 5 hops on my right leg.  The difference between left and right leg of almost half a metre on that occasion was typical of the difference seem in previous measurements.  Today I managed 7.39 metres in five hops on the left, and 7.44 metres on the right.   Thus there has been a deterioration of 24% on the left.  The one consolation is that my two legs are now approximately equal.

The results of today’s test provide a graphic illustration of why I was unable to match Emily on the uphill stretches in the Turkey Trot, and also why my performance in interval session has been so poor.  For many months, the arthritis had made it almost impossible for me to exert much force with my legs, especially my left leg, and my type 2A fibres had atrophied.   In a younger person, I suspect that the 6 weeks of training in preparation for the Turkey Trot would have reversed most of that atrophy, but I am afraid that for a person in his mid-sixties, a more focussed program of strength recovery is required.

So as was the case at this time last year, I will embark upon a program designed to build both type 2A strength and also to improve my aerobic fitness.

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9 Responses to “Atrophy of fast-twitch aerobic muscle fibres”

  1. Ewen Says:

    The hopping test is an interesting one. We used to do hopping as a drill for running, but some years ago. I should try it one sunny day down at Calwell. Do you have a standing or running start? I presume standing, as with running momentum would help you to hop further. I know my type 2A fibres are weak so that might be a good test to check results from short hill sprints when I kick them off.

    • canute1 Says:

      Ewen,
      Yes, use a standing start. I do it on a mown grass surface (my garden lawn), so Calwell should be a good location.
      I avoid using the same hopping action in training so that I am not merely training the specific neuromuscular coordination required for the test. However in the next few months I will be doing different types of hopping exercise (eg line jumps etc) to improve my eccentric contraction ability However I do not do depth jumps from a substantial height as I am cautious about the risk of applying too much stress to my knees.

      Incidentally, I remember well going to hear Arthur Calwell speak when he was leader of the Opposition in the mid-sixties. He was not an elegant politician, but he was impressive in the clarity of his thinking – I thought this led him to a principled position on Vietnam, but in earlier days when he had been Immigration Minister in Ben Chifley’s government (which I scarcely remember) it had led him down a narrow path in supporting the White Australia Policy.

      • Ewen Says:

        Thanks Canute, I’ll try that. I know my hopping would be poor as evidenced by my high jump results. A couple of years ago I could only clear 1.3 metres, when 10-15 years ago 1.5 metres was a reasonable clearance.

        Interesting about Calwell. About the earliest politician I can remember is Harold Holt!

  2. Rick Says:

    Hi canute,
    I started doing plymetrics again, in the hope of getting back some of my strength lost over the years.
    Which plyometrics do you think are the most important for distance runners to do and what do you think of the following videos?



    • canute1 Says:

      Rick
      I think that in general, hopping exercises are the most appropriate plyometric exercises for endurance runners. The main goal is to apply a force that stretches the major leg muscles immediately before they produce an explosive contraction that propels the body upwards and forwards. The force that provides the initial stretch should be similar to the force associated with arresting the body at footfall.

      Hopping on one leg is probably the best as this also helps improve balance and the use of the muscles required to stabilise the body when running. However at present I mainly employ two footed bunny hops to minimise stress on my knees. Also at present I want to use one leg hopping as a test of increased power, and therefore do not want to explicitly enhance the neuromuscular coordination associated with one leg hopping, but anticipte that in the longer term, one leg hopping will be part of my routine.

      The intensity of single leg hopping can be increased by hopping up-hill. I would be very cautious about one leg hopping downhill.
      I increase the intensity of two footed hopping by hopping over a series of very low hurdles (6 inches high).

      Neuromuscular coordination can be improved by incorporating different directions. I also do line jumps ( a two-footed forward hop over a line or a low hurdle alternating with a backward hop.)
      Thanks for the links to the videos. I will look at them as soon as I have a few spare moments

  3. Rick Says:

    Thanks Canute.
    Seasons greetings and good health for 2011

    • canute1 Says:

      Rick

      I hope you had a good Christmas and that you have a successful New Year – with yet another marathon PB.

      I have had a look at the Terrence Mahon videos and think that they are great. In the second video, he quite rightly emphases small hops for strengthening the feet. It is definitely best to start off with small hops though I think that after the feet are well conditioned it is useful to hop over low hurdles (I used one 6 inch hurdles at present) as this is likely to engage the larger muscles of the leg .

  4. Muscle stiffness and running efficiency « Canute’s Efficient Running Site Says:

    […] the gap on the descents set us up for an exciting duel in the final mile .  A week later, the hopping test confirmed that I had indeed lost a lot of strength in my leg muscles since the recurrence of the […]

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