Seemingly crippling fatigue may strike during an intense workout, a prolonged swim, or a race. A swimmer’s natural tendency is to reduce swim velocity when fatigue occurs, but new research suggests that fatigue is to a large extent a neural phenomenon, rather than a crisis in the muscles. As a result, swimmers can develop effective strategies
which thwart fatigue-related reductions in speed.  HANDLING FATIGUE

If you carry out challenging interval workouts during your swim training, you are studying the true nature of fatigue, without being aware that you are doing so. After all, you have probably had the following experience: You decide on a workout, say 10 X 100 meters in 80 seconds each (we’ve selected a familiar type of training session and an arbitrary time for each work interval). Your warm-up goes well, and you’re off and swimming! The pace you have
chosen is an ambitious one, but you are feeling great the first time through the pool, and you cover the initial 100 in 77 seconds. The second one is 78, the third 79, and from thefourth one on you are struggling a bit to hit your target of 80. For the most part, you stay on track, but one interval, we’ll say the eighth, slides up to 82.

The ninth feels really tough, but you hang in there and produce an 80. You have reached the point in the workout at which fatigue should be close to maximal. After all, you are a believer in the traditional concept of fatigue. You know that as you continue to swim quickly, for one work interval after another, your intramuscular pH is dropping fast, reflecting the tide of hydrogen ions which are flooding your muscle cells (1). That devastating fall in pH is interfering with the release of calcium ions into your muscles’ sarcoplasmic areas (2), making it much-more difficult for your muscle fibers to contract forcefully (3). As a result, adhering to planned pace is becoming a major undertaking.

And then, something magical happens! At the point when muscular fatigue is greatest, when pH has bottomed out, when calcium ions have been locked away for the day, when muscle contractility has ebbed, you uncork your best 100 of the day – a 75! Who said that swimming does not have its magical moments? HANDLING FATIGUE

Huh? If muscle fatigue is truly a function of metabolic events inside muscles, that last 100 should have been the slowest, not the fastest interval of the day. Our views of fatigue – and of what determines swimming pace during workouts and races – must be wrong!

Indeed, that is what recent research carried out at the University of Cape Town, the University of Stellenbosch, and the Sports Science Institute of South Africa is telling us. In this new investigation, eight healthy males (average age = 22 years) completed “anaerobic-capacity” tests in the laboratory on a Monark friction-braked cycle ergometer (4). To gain a better understanding of the nature of fatigue and of pacing strategies during high-power exertions, the South-African researchers used an element of deception with the subjects. Specifically, the young men were informed that they would be completing four 30-second maximal trials, as well as one 33-second and one 36-second maximal effort on the bike. In reality, they completed two trials of 30 seconds, two tests of 33 seconds, and a duo of 36-second exams.

The deception took place in the following way: Prior to one of the 33-second tests, the cyclists were told that it was actually a 30-second exertion, and the same was true for one of the 36-second affairs. The researchers hoped to determine whether the subjects would subconsciously alter pace or strategy during the “informed” 36-second trial (when they were told that the trial would last for 36 seconds), for example, compared with the “deception” 36-second trial, when the cyclists thought they would only be cycling for 30 seconds. The cyclists were allowed to watch a clock during all of their maximal exertions, but – ingeniously – the scientists had programmed the clock to run more slowly during the deception 36- second trial, so that it would tick off 30 “seconds” during what was really a 36-second time frame.

You might expect that the cyclists would ride with more power, at least initially, during the deception-36 trial, compared with the informed-36 trial (since they thought that the deception-36 trial was going to be shorter in duration), but the results were more interesting than that. As it turned out, power output was exactly the same in the informed and deception 36-second trials, right up until the 33-second point, but then power fell significantly over the last three seconds of the deception trial! HANDLING FATIGUE

How should we interpret that? Since the cyclists were able to perform more work when they were reliably informed about the duration of exercise, compared with when they had been deceived, some internal factor, not located in the muscles, must have controlled power output. If “peripheral fatigue”(fatigue centered in the muscles, as according to traditional theory) was the true factor controlling performance, then power outputs should have been exactly the same in the informed and deceived 36-second trials (because the extent of muscle fatigue would have been the same in these two trials of equal duration).

Ordinarily, a fall-off in performance during short-term, high-power tests such as the ones used in this study would be attributed to the selective fatiguing of fast-twitch muscle fibers, the ones used for such high-intensity efforts (5). We hear this constantly in the world of swimming – the notion that fatigue of fast-twitch fibers is what causes significant slow-downs during intense exertions. But this can not be the explanation for the fatigue displayed during the last three seconds of the deceived 36-second trial, since it was the same duration as the informed 36-second trial, and power output up until the 33-second mark had been the same in the two cases.

Furthermore, the drop in power after 33 seconds in the deceived 36-second test had to be solelythe result of a drop in cadence on the bike (6). As you know, muscles are not smart enough to say “Heyfellahs – we’re getting tired. Let’s slow down our rate of firing!” That rate of firing, which determines rpm on the bike (and the rate of stroking in swimming), is controlled by the nervous system, not the muscles, suggesting – again – that an internal mechanism was at work to control power and make it look as though muscular fatigue was occurring. What seems to happen is that the brain - on an unconscious level - anticipates the effort which willbe appropriate during an exertion before the exercise actually begins and then modulates effort during the activity to make sure it does not rise above the subconsciously chosen, “appropriate” intensity (7). This probably has a kind of survival value, protecting the integrity of the muscles, which might otherwise be seriously damaged during very strenuous exertion (8).

However, the “appropriate” intensity can be re-set subconsciously by the brain during exercise if something changes. In the South-African study, for example, the brains of the cyclists realized – via a process which was definitely below the level of conscious thought - that the informed 30-second duration had been exceeded, even though the clock on the wall said otherwise. Once this realization occurred (apparently about three seconds after the announced 30-second duration had been surpassed, indicating a kind of “lag effect”), the cyclists’ brains re-set the intensity (to a lower level) for the longer-duration effort, and power dropped off, not because of problems in the muscles but because of this nervoussystem re-setting. HANDLING FATIGUE

Indeed, during exercise there appears to be a pre-programmed, neural “end point” which may be quite different from the true muscle-fatigue end point. Once the anticipated end point is reached, power output will fall dramatically (as it did after the 33-second mark in the deceived cyclists).

This kind of thing takes the mystery out of what appeared to be the paradoxical results obtained in other scientific investigations which examined neuromuscular activity during all-out efforts. Such results showed that a significant part of the drop-off in power at the ends of such exertions was caused by a decline in iEMG activity, in other words by a decrease in the extent to which muscles were stimulated by nerves (9 & 10).

And of course the South-African findings explainwhat happened in your 10 X 100 swim-intervalworkout (described above). Your amazing surge during the last 100 of the day did not occur because muscular fatigue suddenly vanished, with intramuscular pH rising, calcium ions doing their thing again, and basic muscle contractility restored. No, your nervous system decided: “Hey, there’s just one more interval to go. It’s safe to loosen things up a little bit and swim according to our true abilities!” And so, instead of stroking conservatively along within your cerebral-dictator's, overly restrictive, subconscious, protective noose, you swam like a tropical cyclone, temporarily freed from your nervous-system’s shackles.

By the way, the short (close-to-30-second-induration), maximal exertions engaged in by the cyclists in this South-African study were basically “Wingate Anaerobic Tests.” For the past 30 years orso, exercise scientists have used Wingate Tests as a way to quantify an athlete’s “anaerobic capacity” from the standpoint of power output. Conventionally, a Wingate Test utilizes a 30-second protocol on the bike, during which subjects are asked to cycle as intensely as they can for the full 30 seconds. HANDLING FATIGUE

This test was thought to measure anaerobic capacity because it was believed that 30 seconds was too short a time for “aerobic processes” to play a significant role. Interestingly enough, conventional wisdom also held that all the energy utilized during the first five to 10 seconds of a Wingate Test came solely from the alactic, phosphagenic energy pathway (i. e., entirely from ATP and creatine phosphate). The energy used for muscle contractions in the final 20 seconds of the 30-second Wingate was believed to come exclusively from anaerobic glycolysis (the breakdown of glucose to pyruvate and lactic acid, without the participation of oxygen). Today, most swimmers and swimming coaches would still agree that this is quite-reasonable thinking.

However, research has shown that such beliefs are incorrect. Notably, lactate accumulation occurs within the first 10 seconds of a Wingate Test, revealing that anaerobic glycolysis is operating during that initial time frame (11). In addition, investigations reveal that aerobic metabolism (mitochondrial oxidative ATP synthesis) is turned on in the first few seconds of the Wingate Test (12). This of course calls into question the view that the Wingate Test is a measure of “anaerobic capacity.”

The Wingate Test, originally designed merely to measure “anaerobic power” (13), has instead become a kind of mini-lab in which one can study fatigue (it’s clear that it is not really measuring anaerobic power, since aerobic processes are in play during the 30 seconds of activity). Careful analyses of Wingate performances reveal that falls in power over the 30-second period are almost entirely the result of a decline in cadence (stroke rate in swimming); to put it another way, the nervous system is re-setting intensity of effort as the Wingate proceeds (as mentioned previously, muscles can not regulate cadence). Indeed, iEMG recordings have demonstrated that the nervous system stimulates the muscles to a lesser degree toward the end of a Wingate, compared with the beginning.

What does this mean for your swim workouts and competitions? First, don’t “give in” to fatigue during your interval sessions and tough, sustained swims (not to mention your races). Remember that fatigue is to a large degree a mental construct, rather than a point beyond which muscles are truly incapable of continuing (studies show that significant fatigue can occur even when only 20 percent of the fibers within a muscle are being recruited; it is hard to imagine that true muscle fatigue is taking place when 80 percent of a muscle’s cells are not even being utilized). So, when fatigue occurs, thank the fine fellow (for attempting to protect you), but remember that your muscles are still OK, and remain relaxed and very focused on achieving your target pace. You can over-ride your internal regulator and overcome fatigue by focusing fiercely on making your muscles work. This is what you routinely do during the last high-quality segment of a very tough interval workout, and you can routinely pulloff this fatiguefighting magic once you have understood the true nature of fatigue. HANDLING FATIGUE

In a race, for example, when your arms, shoulders, and legs begin to feel either rubbery or fence-post-like, avoid the defeatist attitude which often comes along with such sensations. Instead of thinking that you’re in trouble, instead of internalizing the message that your possible PR is lost, remind yourself that much of that rubberiness is related to a reduced iEMG – your nervous system is not stimulating the muscles fibers in your legs, shoulders, and arms as much as it did when the race began. So, fire up your brain, settle right back into your planned pace, relax, and hang in there. Yes, you won’t feel so good (your brain will try to protect you by making quicksilver paces feel too tough), but as you relax and continue to hold the desired speed, the protective portion of your brain will unwind and you will find it much easier to keep going.

The new research also suggests that famed Hungarian running coach Mihaly Igloi was a genius – or not. Igloi, who coached such stand-outs as Lazlo Tabori, Jim Grelle, and Bob Schul (the only U.-S.runner to every win an Olympic gold medal at 5000 meters), was somewhat famous for not revealing to his athletes the full extents of their workouts at the beginnings of the sessions. This may have created a situation in which Mihaly’s runners treated eachinterval or sustained surge in isolation; thus the sole mental goal may have been to finish the fiery blast at as high an intensity as possible, without concern for what followed (no internal regulator in the nervous system tried to dampen the level of effort). But – it’s also possible that the runners held back a bit during early stages of their workouts, knowing that Mihaly had probably dreamed up a huge assortment of thingsfor them to do.

The bottom line for you? Don’t be a traditionalist: Remember that the fatigue you are feeling usually does not represent some kind of crisis in your muscles. In most cases, a significant portion of your fatigue is simply the result of your nervous system’s attempt to act like a “mother hen.” Deal with the fatigue objectively, and don’t view fatigue as an inescapable blockade which will inevitably thwart your efforts. When fatigue strikes, relax, tell yourself that you are going to be OK, and swim hard. ©

To learn about Handling Fatigue During Rugged Swims, or Secrets Of Swimming The 10K (the full articles can be read by purchasing Vol. 2  Issue 4 of Swimming Research News) and many more swimming related topics, simply click-on the Back Issues link, and select the volume and issues number, from the drop-down menu, or type in another topic of interest. A subscription to Swimming Research News is another way to receive valuable information about swimming. BUY NOW.