Amongst our different groups of cross-country skiers, being in good shape usually means having good endurance. Good endurance can however be measured in a couple of ways, one being able to ski slow, but steadily for a long distance, another being able to ski fast in a ski race. Different body mechanisms are required for the two “types” of endurance. Both types of endurance require training that changes the body at the muscular level, while the ski racer must also stress the cardiovascular system to become faster. To ski fast in a ski race means you also have to train fast — sometimes.
The cardiovascular system in simple terms includes the circulatory system of the blood being pumped by the heart around the body through arteries, capillaries and veins. Along the way the blood “picks up” oxygen in the lungs, and delivers this oxygen to the working muscles in the body. Through a proper training regime this “delivery” system can be improved by:
– increasing the strength of the heart pump
– increasing the size of the heart chambers
– increasing the artery size and capillary density
– increasing the efficiency of oxygen exchange and utilization
– increasing the tolerance and removal of lactic acid and other byproducts of high intensity exercise
When ski racing under normal circumstances, it is the concentration and accumulation of lactic acid that eventually inhibits muscle contraction and causes fatigue. The time and rate of accumulation depends on the individual skier’s “endurance training” status. The intensity threshold at which the accumulation of lactic acid becomes “exponential” is often called the Anaerobic Threshold (AT). Since racing at intensity above this “red line” causes rapid fatigue, it would seem logical and most beneficial to “move” this red line higher, such that a higher speed can be maintained without becoming fatigue.
, and demands more energy than most other sports. The human cardiovascular system was not designed to support the demands of “four-legged” movement, and does not have the big heart-pump of racehorses or sled dogs. It is therefore very important for skiers to build a good base of strong oxygen transportation and delivery system, and an efficient energy production system. This is done by high volumes of low intensity training that builds the muscular foundation, such as increased mitocondrial density (“energy producers”), increased capillary density (“better oxygen exchange”), and enhanced enzymes that take part in the fat metabolism (“saves high energy glycogen”). These muscular changes take several years to be fully realized, and may be the reason many cross-country skiers keep getting stronger with age.<br />
Over time, long “over distance” training at low intensity will build a muscular endurance foundation that is necessary to support and allow more intense “cardiovascular training” to take optimal effect. We often refer to “cardiovascular training” as interval training or anaerobic training.</p>
<p>Intensity chart<br />
<TABLE BORDER CELLSPACING=1 CELLPADDING=5 WIDTH=100%><br />
<TR><br />
<TD VALIGN=) Intensity scale | Intensity as a % of max HR (MHR*) | Training method | Comments |
| 1 | 60 — 70 % | Long distance, any method | Very important for building muscular endurance foundation |
| 2 | 70 — 80 % | Medium distance, poor conditions | Gives least return for the effort |
| 3 | 80 — 85 % | Easy intervals, natural intervals | Limited use, mostly during base training |
| 3 — 4 | 85 — 90 % | Medium hard interval training, "race pace" training | Very important for improving AT |
| 4 | 90 — 95 % | Hard interval training, above race pace speed, short races | Very important for improving AT |
| 5 | 95 — 100 % | Max effort, sprints | Very small part of overall training |
To understand the intensity level required for interval or anaerobic training is may be useful to show a training intensity chart.
*Max heart rate (MHR) values are very individual, and can be measured after two or three 2 minute long interval bouts ending on top of a hill. Without a heart rate monitor, the pulse should be counted for 10 seconds, then multiplied by 6. Adult athletes’ MHR can vary from 165 — 220, and does not change much from year to year.
Anaerobic threshold training
Test and research have shown that the anaerobic threshold (AT) is between 85 — 95 % of MHR for most skiers. This threshold is, as mentioned above, the intensity level where rapid accumulation of lactic acid starts (for skiers usually around a blood lactate concentration of 3 — 4 mM). At intensities lower than this threshold, the body is able to remove or even metabolize the lactic acid, and stay “in control”. Since the AT is what causes fatigue and inhibits muscle contraction in a race situation, a ski racer’s goal should be to “train” the threshold to become closer to 95 % rather than 85 % of max heart rate. Here are my basic philosophies for doing so:
– To improve any physiological system in the body, it must be stressed above the normal comfort level
– Since the AT is a “floating” threshold, it is important to train at intensities at both ends of the perceived threshold value
– The efficiency and effect of exercising a muscle is better when the muscle is in a “non-lactic” state, so the majority of interval training should be at intensities just below the AT
– Since a healthy body “super-compensates” after “learning” that it is not strong enough, certain interval sessions should be at intensities above AT, and actually resulting in fatigue by the end
In practical terms, this translates to:
– Do 1 – 2 interval workouts every week, but only if you have a good base of low intensity training
– In early pre-season training phases, and for all intervals above 3 minutes in duration, stay at intensities below the AT (below 85 % of MHR). Typical long intervals are from 3 — 8 minutes. The rest period between the interval bouts should be about _ the duration of the interval bout itself.
– Closer to race season, do some interval sessions at intensities above AT, but keep the bouts at or below 2 minutes. Typical short intervals are from 30 sec — 2 minutes. The rest period between the interval bouts should here be at least the time of the interval itself.
– Once every 3 weeks, do a “race pace” workout (or a race) where the intensity stays as close to the AT as possible (for example at 85 — 90 % for 20 minutes)
– The total duration of an interval session should be between 10 — 20 minutes (not counting the rest periods between the interval bouts). For example, 10 x 1 minute above AT intensity, or 5 x 4 minutes below AT intensity.
Good luck, and if you’re a ski racer, remember: No pain, no gain!
