More thoughts on elliptical cross-training

In my post yesterday I suggested that although elliptical cross training might have many benefits for the runner, it might not be good for promoting the required neuromuscular coordination.  Ewen asks whether one factor is the lower cadence on the elliptical. In fact I aim for an elliptical cadence in the range 80-90 complete gait cycles per minute which is similar to my cadence when running (around 90 left steps and 90 right steps per minutes).  I did some testing of my efficiency (i.e. heart rate v power output) at different cadences and found that there is not a great deal of difference between 70 and 90 gait cycles per minutes.  Around 80 appeared marginally more efficient than  70 but not much different from 90.  However,as I mentioned yesterday, the striking difference between elliptical cross training and running is the amount of downwards push required, presumably due to the lack of elastic recoil on the elliptical.

 

Although the action of elliptical is intermediate between running and cycling insofar as the involvement of trunk muscles on the elliptical is similar to running (especially if you do not use the handles), the leg action on the elliptical feels somewhat similar to cycling.  I am not a triathlete, but I understand that for the first few minutes after the bike-to-run transition, running feels awkward, and that this awkwardness can be at least partially reduced by increasing cadence towards the end of the cycling.  I suspect that the awkwardness is due to the change  from recruitment of fast twitch fibres employed to power concentric contraction, to a greater dependence on slow twitch fibres and eccentric contraction.   (I would be interested to know what triathletes understand about this).

 

If the downwards push on the elliptical is similar to that of cycling, then an immediate transition from elliptical to running will have some of the problems of a bike-to-run transition.   As in the bike-to-run transition, the problem might be diminished by high cadence on the elliptical, but I suspect it will always be at least a minor problem.   I sometimes use the elliptical at high cadence and low resistance to warm up for running on very cold days.  I believe it does promote muscle blood flow and joint lubrication, but I have been surprised to find that I still need to do a running warm up before I can run fluently.  Whether or not elliptical training one day affects neuromuscular coordination the next day, I d not know, but in view of the theoretical possibility of interference, I would advise a good warm up for the running session to establish good neuromuscular coordination.

 

Related to the issue of the greater push on the elliptical is the likely greater development of fast twitch fibres.  Ewen asks how well these fibres can be recruited aerobically.  The distinction between aerobic and anaerobic function is not an all-or-nothing distinction.  I suspect a moderate degree of hypertrophy of fast twitch fibres is useful for all except ultra-marathon runners.  Whenever stride length increases beyond about 1 metre, a quite appreciable push is required to launch the body along the required trajectory, and as I mentioned yesterday, elastic recoil is not adequate to achieve this.  (Since passing age 60 I have become increasingly aware of the need to push to achieve a fast pace – maybe this would be heresy to the Pose School, but until I meet an elderly Pose runner who can run fast, I will be inclined to hold onto my current opinion). At cadence of 180 steps (i.e. 90 left, 90 right) per minute, paces faster than about 5.5 min/Km require a  stride length greater than 1 metre.   A pace of 5.5min per Km, which is only a moderate marathon pace, is below lactate threshold pace for many runners, so as far as I can judge, an appreciable concentric push is required even when running in the aerobic zone.  I suspect that this is best achieved using fast twitch fibres.

 

So in conclusion, I think that the greater amount of concentric push on the elliptical might cause neuromuscular coordination difficulties during an elliptical-to-run transition, but might produce greater fast twitch hypertrophy which would be beneficial provided it is not excessive.

 

Two days ago, Ewen asked if I thought that my decreased heart rate at a given power output on the elliptical might translate into a lower heart rate at lactate threshold when running.  I do not think this is likely.  Instead I would expect that an increase in mitochondria, increased capillary density, increased pumping capacity of the heart, and increased ability to metabolize lactate would all lead to a faster pace and an increased heart rate at lactate threshold.  I would regard this as a benefit.  I just hope it is true.

Transfer of the benefits of elliptical cross-training to running

As usual, Ewen raises the important question about my post yesterday about improvements in aerobic efficiency during 3 months of elliptical cross training.  He asks whether or not the observed improvement would be expected to result in a lower heart rate in the vicinity of lactate threshold when running.  Implied in this question is the more general question: will the observed improvement in aerobic fitness lead to improved performance when running.  I do not know.

 

The definitive proof of the pudding will come when I test myself in a race.  However, many factors affect race performance. In my case, my tendency towards asthma places me at the mercy of my only partially controllable bronchi, so a particular race might be more influenced by daily fluctuations in the irritability of my bronchi than by overall change in aerobic fitness.  Therefore I need a test that is relatively unaffected by variable outside air temperature and humidity, and the muddiness of the terrain; and furthermore, produces little DOMS so it can be applied fairly frequently, allowing averaging to minimize the effect of daily fluctuations.  That is why I developed this elliptical test for aerobic fitness.  The dilemma is that I can only speculate on the likelihood that the gains in aerobic fitness on the elliptical will transfer to fitness for running.  I am still evaluating the relevant evidence, but here are my currents thoughts.

 

The goals of aerobic conditioning for running are:

1)      Increasing the number of mitochondria in muscle fibres. The mitochondria contain the enzymes that carry out oxidative metabolism; that is the combining of glucose with oxygen to generate relatively large amount of energy.  Increasing mitochondria should increase the ability to generate energy efficiently, provide enough oxygen and glucose can be delivered to the muscles.

2)      Increasing the efficiency of the heart as a pump.

3)      Promoting development of new capillaries in muscle so that blood (and hence oxygen and glucose) can be delivered to muscle fibres at a higher rate.

4)      Increasing the ability to metabolise lactate.  When the rate of supply of oxygen is insufficient, energy is produced by anaerobic metabolism  in which glucose is converted to lactate.  Although  this process is the dominant process once the ‘anaerobic threshold’ is exceeded, in fact this threshold is not an all-or-nothing threshold.  In the upper part of the aerobic zone, when oxygen delivery is not quite adequate, a certain amount of lactate is produced.  Build up of lactic acid leads to eventual transition into the anaerobic zone that can only be sustained for a limited time before rising acidity impairs muscle function.  This build up might be delayed if the ability of muscles and perhaps other tissues to remove lactate, is increased. In fact, lactate is also oxidized in mitochondria, so enhanced mitochondrial function should help delay the build up of lactate.

5)      Improving neuromuscular efficiency – the ability of the central nervous system to recruit muscles in the most efficient manner.

6)      Re-modelling of tendons, ligaments and bones to withstand the stresses of running

7)      Hypertrophy of muscle fibres.  During aerobic conditioning, I believe that the main mechanism of increase in the strength of muscle is likely to be the increase in mitochondria and capillaries listed above; during anaerobic resistance training, hypertrophy is due to incorporation of additional protein into muscles.  It is nonetheless probable that some strengthening of contractile proteins occurs during aerobic conditioning.  The skinny legs of many elite distance runners suggests this strengthening makes only a minor contribution to fitness for distance running, but even a distance runner needs to be able to exert  at least a moderaltey powerful downwards push at the end of stance because elastic recoil is far from 100% efficient and therefore elastic recoil is unable to supply an adequate push to propel the body along the required trajectory in the airborne phase. 

 

So which of these processes is likely to be enhanced by elliptical cross training, which are likely to be unaffected and which might actually be harmed?

 

Development of the heart as a pump is likely to be similar for a similar work elliptical work load as for running.  Development of mitochondria and capillaries is also likely to be similar, though  there is a possibility that the development will be a little more focused on fast twitch fibres, because the concentric contractions characteristic of the elliptical training are a little to likely to recruit fast twitch fibres. The development of ability to metabolise lactate is likely to be similar for the two types of training.

 

Elliptical training is unlikely to be effective in fine tuning of neuromuscular coordination for running.  The ability to capture the gravitational energy associated with the vertical oscillations of running, in the from of elastic energy that can be recovered at lift-off, is a crucial factor in efficient running.  The elliptical does not develop the exquisite neuromuscular coordination required for this.  Similarly, elliptical cross training does not provide much stress on tendons, ligaments  and bones, and hence will not be very effective in remodeling these structures to withstand the stress of running.  On the other hand, as I discussed in my post about reactive oxygen on February 5^th,  the benefits of running might be offset by permanent damage to muscle fibres.  Such permanent damage appears to be less likely with elliptical training on account of the lesser amount of eccentric contraction.

 

Finally, I suspect that elliptical training might actually produce greater hypertrophy of muscle due to incorporation of protein in the contractile machinery with the muscle fibres, than running.  Because there is minimal elastic recoil, the elliptical demands a stronger downwards push by the leg muscles. I suspect that this will be more effective in producing hypertrophy of fast twitch fibres.  Too much hypertrophy of fast twitch fibres might be harmful, though at least for oldies like myself, in whom deterioration of fast twitch fibres is likely to play a major part in the shortened stride that makes us slow, I think a moderate amount of development of fast twitch fibres is probably beneficial.

 

Summary

So in summary, elliptical cross-training is likely to increase the pumping capacity of the heart, increase mitochondria and capillaries in muscle and increase the capacity to metabolise lactate.

 

It is unlikely to do much to strengthen tendons, ligament ad bones, but on the other hand, is also much less likely to cause permanent damage to either these connective tissues or to muscles.  It will not refine the exquisite neuromuscular control required to capture gravitational energy as elastic energy, and to recover via recoil at lift-off when running.

 

It might promote a slightly greater degree of hypertophy of fast twitch fibres than an equivalent amount of running.  I am inclined to think that on balance this might be beneficial, especially for older runners.

 

As Ewen suggests, it might be useful to replace the training session the day before a high quality running session with an elliptical session to help ensure that the muscle are in good shape for the high quality session.  However, in the warm up for the quality session, it is probably all the more important to include some brief bursts of running at the quality training pace, so as to recover optimal neuromuscular coordination for running at that pace.

 

Most of this is speculation.  I hope that when the spring arrives my bronchi will allow me to assess the fruits of my elliptical sessions, in a 10K race.

Snow drops and improved aerobic fitness

I am just back from an easy 10K run in the woods and along the river bank. We are now at the mushy end of a thaw that set in two days ago. At the edge of the village, two slumping lumps of snow are all that remain of a snowman and his partner; a sad demise on St Valentine’s day.  In the woods a few drifts of mushy snow remain and some mini ice floes float in scattered puddles, but the paths are mainly mud. 

 

Staying upright is almost as difficult as it was on the sheets of icy snow last week.  Mud does not raise the spirits in the way that snow does.  However, the clumps of snow drops in full bloom provide some compensation and the thick green carpet of bluebell shoots indicate that spring is not too far away.

 

The River Trent is in spate, swollen with melt-water but still far from bursting its banks.  Nonetheless, the ancient mill race on the escarpment side of the riverside path, but connected to the river by a tunnel, is full of water.  On account of the mud it took some time before I developed a good rhythm, but in the final few Km I was running fluently and comfortably at about 5:30 min per Km.

 

In November, at the time when I decided to re-introduce several elliptical cross-training sessions into my weekly schedule, I had developed a simple test of aerobic fitness.  I record heart rate in the final 15 sec of a series of consecutive 2 minute intervals.  At the beginning of each interval I increase the resistance but maintain a constant cadence so that power output increases in a series of 7 steps spanning the aerobic zone.  Before my run today I did this aerobic test as a warm up, and was pleased to find that my heart rate at each level of the test is about 12 BPM lower than it was on November. 

 

In part this improvement is due to the fact that my asthma is much better today.  There was scarcely a trace of a wheeze. My performance on this test fluctuates day by day depending on how wheezy I am.  It is probable that I will not do as well in future on days when the wheezing is worse.  However even if I were to take the average the most recent three tests and compare with the average of three tests done in November to smooth out the daily fluctuations, there would still be a definite improvement, perhaps by around 5 BPM at each level. 

 

 

Heart rate v power on the elliptical cross trainer

 

 

 

 

This improvement has occurred over a period of three months during which I have done 2 or 3 easy (or moderate intensity) running  sessions and 3 to 5 elliptical sessions per week, apart for a few weeks in which training was curtailed by injury.  The majority of the elliptical sessions have been in the upper part of the aerobic zone (30 – 35 sessions over the three months). I have done a total of 5 sessions in which I exceeded lactate threshold, and 4 sessions in the lower or mid aerobic zone. 

 

One good thing about elliptical training is that it does not produce any appreciable leg muscle soreness on subsequent days.  This is almost certainly because of minimal eccentric contraction.  The lack of eccentric contraction during the elliptical sessions will probably have resulted in some de-conditioning of my legs, and it is unlikely that I could run anywhere near my potential best over 10K or a half marathon at present.  The interesting question is how much running will be required to re-condition my leg muscles for running.  Whatever the answer to that question, it is pleasing to know that I have been able to improve aerobic fitness substantially without stressing my legs.  

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 4×1Km 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.

Intervals again, and some thoughts about cross-training

Today I resumed moderate intensity running sessions after a period of lower intensity training due to a respiratory infection and its aftermath. I did a 4×1Km interval session on the riverside path, aiming for mean HR 142 (around 90% of HR maximum for an old-timer like me). On the first repetition, the breeze was behind me and I went too fast (4:13 per Km, with mean HR 145) but then settled down well to achieve mean HR 142 on the subsequent three repetitions, giving an overall mean HR of 143 and mean pace of 4:20 /Km. This is similar to my performance a week before I was smitten with a respiratory tract infection in early December, when I achieved a mean pace of 4:21 /Km at mean HR 142 in a 6×1Km session. Today’s session felt a little harder – probably because I had started too fast – but overall, I am pleased that I have not suffered any appreciable loss of fitness during my period of illness and convalescence. In fact I hope that my aerobic base fitness might actually have improved a little as a result of the relatively large volume slow running over the holiday season.

During my convalescence I have also done an increased amount of cross training on the elliptical cross trainer. The elliptical cross trainer is probably an excellent mode of exercise for non-athletes who wish to maintain a moderate level of aerobic fitness with minimal risk of injury. However, it is not clear how useful it is for runners. The available evidence is sparse. One study from the Human Performance Lab at Appalachian State University indicates that performance in a 3Km time trial deteriorated by 48 seconds during 5 weeks of elliptical training that included one lactate threshold interval session, one sprint session and 3 or 4 easier sessions per week, but no actual running. A comparison group who did ‘off season’ running training during the 5 weeks actually improved their 3K run time by a small amount (9 seconds – not a statistically significant improvement, but certainly not a deterioration). So it is unlikely that the elliptical alone is much use for preparing for a race (Honea and Dumke, www.osr.appstate.edu/present/documents/Honea-student_research_poster.ppt).

However, my own preliminary observations led me to wonder whether or not the elliptical might have a useful role. I found that I reached ventilatory threshold at a lower heart rate (and greater perceived effort) on the elliptical compared with running. My first impression was that this merely confirms that elliptical cross-training is a less enjoyable way of getting out of breath. This conflicts with the claims of the manufacturers who emphasize that perceived effort is less on the elliptical, but I think those claims mainly apply to non-runners working at a level well below lactate threshold, where the smoothness of the ‘ride’ is indeed quite relaxing.

But I was intrigued to understand why the ventilatory threshold appears to occur at a lower heart rate. This suggests that more lactate is produced at a given heart rate, implying that anaerobic metabolism of glucose kicks in at a lower heart rate.

To investigate this further I searched the sport medicine literature and found a recent study by Garlatz and colleagues from Western Washington University (The FASEB Journal. 2008;22:1175.2). In a group of trained distance runners they found that at 90% of Working Heart Rate Range, perceived effort was higher but oxygen consumption lower on the elliptical cross-trainer compared with the treadmill. This confirms my own observation, and strongly supports the hypothesis that there is a higher proportion of anaerobic glucose metabolism at this heart rate on the elliptical.

In retrospect this is easy to understand. The action of the elliptical involves a strong push, especially by quadriceps which are active though most of the gait cycle, whereas the quads are only active for a small part of the gait cycle when running.  However when running the quads suffer a lot of stress because they work hardest when being stretched at footfall – and this generates the micro-tears that might cause DOMS the next day. In other words, on the elliptical, the quads do more work but it is different in nature and potentially less damaging in comparison with running. It is likely that the additional work recruits a higher proportion of fast twitch fibres which tend to metabolise glucose anaerobically. Thus elliptical cross training might be a very good way to improve the body’s capacity to handle lactate with relative little damage to muscles.

If you want to run a fast 3K, you really need to train your muscles to cope with large eccentric loading. The elliptical is probably not much use for this but may nonetheless have a useful role to play in improving the capacity to metabolise lactate with minimal damage to muscles.