Archive for December, 2012

Can an awesome race face fool the central governor?

December 27, 2012

As described in recent posts, over the past two years it had become increasingly clear that leg muscle atrophy has been limiting my running speed.  So for the past 8 weeks I have been lifting weights, three or four times per week to increase my leg muscle strength.  My primary focus is on barbell squats and dead-lifts.  These lifts provide a whole body work-out, though the major load is borne by the quads, the posterior chain (hams, glutes, hip adductors) and trunk muscles.  I started with the empty bar (20Kg) while learning safe technique and then progressively incremented the weight. After a warm up with light weights, I do 5 sets of 5 reps with the squats and 1 set of 5 dead lifts at my 5 rep maximum.  I am now lifting over 90 Kg, which is around 150% of my body weight, in the squats and a little more in the dead-lift.

During this period I have cut back on the amount of running to about 25-30 Km per week in order to avoid undue stress on my legs.  I find that the heavy lifting leaves my leg muscles feeling sluggish and lacking the springiness required to cope with the eccentric loading incurred during running. However, the elliptical cross-trainer demands much less little eccentric loading of the muscles; so for several weeks I have been doing high intensity interval sessions on the elliptical to maintain aerobic fitness, but I have lost some of the endurance I had built up in the summer.  I will have to re-build this in the spring

At this stage I have been pleased with the increases in strength produced by my lifting program.  While lifting 150% of body weight would be  very modest achievement for a dedicated weight-lifter, it is not bad for an elderly person with the spindly physique of a marathon runner.  I have gained about 1 Kg in body weight.  It is probable that I now have near optimal strength to weight ratio for an endurance athlete.   It is too soon to know what effect this will have on my running.  I need to do a few weeks of power lifting (with lighter weights and faster movement) and plyometrics early in the New Year to increase the speed with which I can recruit my strengthened muscle fibres  Then I will be ready to assess whether or not the increased strength has produced the anticipated increase in running speed.

Maximising muscle recruitment

The experience of lifting near maximum weight has focussed my mind on tricks for maximising muscle recruitment.  While a lot of the noisy exclamations that reverberate around a gym appear to be mainly for show, even serious lifters grunt when lifting at near maximum capacity.  Studies indicate that this produces a modest increase in the maximum lifting capacity.  In part this grunt reflects the fact that it is essential to maintain a high intra-abdominal pressure to stabilize the trunk during the lift, for both dead-lifting and squats, so expiration is performed though an almost closed glottis.  However, it is probable that some of the benefit comes from the psychological effect.

In recent years, the grunts by female tennis players, perhaps most notably Maria Sharapova, have been a bone of contention with opinions ranging from Martina Navratilova’s view that it is cheating because it disguises the potentially informative sound of the ball on the racquet, to coach Nick Bollettieri’s claim that it serves a similar torso-stabilizing purpose as the grunt of the weight-lifter.  I understand that Jimmy Connors was the one who introduced grunting into grand slam tennis, and many others including Andre Agassi, Monica Seles, and the Williams sisters have followed, but Sharapova employs it with greater dramatic effect.   The possible mechanical benefits from stabilizing the torso by forceful exhalation against a closed glottis appear to be only a minor justification for her 100 decibel shrieks.

Hyperventilation

Because I am only lifting at 5 rep maximum (about 90% of 1RM) I do not grunt.  However I have been aware  that as I prepare to begin lifting I take a couple of short deep inspirations before the final sustained deep inspiration required to maintain the intra-abdominal pressure necessary for heavy lifting.   Is this hyperventilation just a delaying manoeuvre to give me a few seconds to psyche myself up for the effort, or does it serve a physiological purpose?

In many circumstances, hyperventilation is a bad strategy.  At rest, it can produce a syndrome characterised by palpitations, dizziness, and tingling sensations.  In susceptible individuals, it triggers panic.   These effects are largely due to the clearing of carbon dioxide from the blood, thereby making the blood more alkaline.   But the full array of effects produced by hyperventilation is complex, and includes many ‘central command’ effects.  Some of these are reflect brain-stem reflexes, while others reflect the effects of low carbon dioxide levels on brain regions including hypothalamus, hippocampus, other limbic areas and locus coeruleus that control the autonomic nervous system.  Hyperventilation produces a rise in heart rate; increased cardiac output and increased blood flow to limb muscles.

Lifting near maximal weight demands tensioning of limb and trunk musculature, and I suspect that my spontaneous hyperventilation as I prepare to lift is an unintentional ‘trick’ to generate the required tension.  In effect, the surge of alkaline blood encourages the control systems in the brain to release the brakes and allow maximal recruitment of muscles.

I have also noted in the past that when I wish to increase power output when doing high intensity interval sessions on the elliptical cross trainer, I automatically increase ventilation a fraction of a second before I increase power output.    It appears that when I do this that increased power is a consequence of increased depth of respiration rather than increased pace producing a passive increase in respiration.   In other words, a signal associated with increased frequency or depth of breathing promotes increased recruitment of muscles.

Tim Noakes’ concept of the central governor has been a controversial topic. Maybe it would be over-simplistic to imagine the  ‘governor’ as a miniature pilot embedded in the non-conscious recesses of one’s brain, but there are undoubtedly a number of mechanism mediated by blood-borne chemical messengers and the autonomic nervous system which together act to adjust muscle recruitment.  Furthermore, these mechanism appear to by modulated to allow for anticipated future demand.  For practical purposes, I find it helpful to regard this set of automatic control mechanisms as a prudent governor which generally acts to optimise my performance, but occasionally needs cajoling to relax when it becomes over-conservative.  In some circumstances, hyperventilation can be a useful trick that encourages the ‘governor’ to increase cardiac output and muscle recruitment.

Breathing while running

But what about when running?  Here we encounter conflicting demands.  As Usain Bolt cruised to Olympic gold in Beijing he exuded a sense of relaxed power.   There was no sign of needless muscle tension nor hyperventilation.  Sprinters usually hold their breath from the set position and typically exhale only once during the first thirty metres.   For long distance runners, deep breathing from the diaphragm is required.   I allow my breathing rate to adjust itself according to demand, but  usually find that I am employing a 3-3 pattern (three steps during inhalation; three during exhalation, corresponding to a breathing rate of around 30/min) when running in the mid-aerobic zone, and 2-2 pattern when near the second ventilatory threshold (10K pace).  However in the final sprint I usually increase automatically to 1-1.  When breathing simply follows demand it should not be described as hyperventilation, which by definition is breathing in excess of oxygen requirements.

Can hyperventilation be useful for a runner?

However other experiences leave me wondering whether there are times when a runner can use hyperventilation to advantage.  In the Robin Hood half marathon in September, I had been struggling to raise the tempo of my running throughout most of the second half of the race.  With 3 km to run, my conscious brain was still fruitlessly commanding my legs to go faster, but my non-conscious brain was countermanding the order.  The first photo (taken from my blog describing the race) illustrates the fruitless struggle between conscious will and leaden legs.

ApplyingPressurewith3KmToRun

But then with 100m to go, I resorted to the hyperventilation trick.  I deliberately increased breathing rate to a 1-1 pattern to jump-start an all-out sprint.  I was subsequently amused and a little dismayed when I saw the second photo.  The facial contortion and tension in the accessory muscles of inspiration in my neck create an impression of needless waste of energy.  Almost certainly the amount of tension was somewhat excessive, but the crucial fact was that I felt energized and powerful.  Despite my grotesque facial appearance, the ‘central governor’ had relaxed its leaden grip and released the shackles from my ankles.

The final sprint

The final sprint

This trick wouldn’t have worked with 3 Km to go.  At that stage, the governor’s  determination to conserve my meagre reserve of energy would not have been so easily brushed aside.  But with 100m to go, there was no longer any need for such tight control.  What was needed was a stimulus to trigger a gear shift.  The combined physiological effects of increase cardiac output and decreased peripheral vascular resistance produced by the hyperventilation created a surge of blood to the muscles that provided the required trigger.   In the overall strategy of racing a half marathon or marathon, the final 100m has a trivial impact on the time recorded, but it is satisfying to claim a final few scalps and move up the finishing order.