It’s that time of year when it starts to feel like the snow is never going to go away, the air is never going to warm up above freezing, and we’re doomed to a lifetime of trainer rides and treadmill runs. Maybe we’re being a bit dramatic, but hey, that’s what cabin fever does. But fear not, spring is on the way, and probably sooner than you think. In the meantime, these three winter swim sets, three indoor bike workouts and four treadmill runs can help keep you from going stir-crazy. The workouts described here are very good ones for when you can’t get outside, and you will do well to sprinkle them into your indoor training program this winter.

RELATED: Triathlete’s Guide to Indoor Training

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Pool Workouts for Triathletes

The following intervals are based on the fastest average pace you can hold for 10x 100-yards freestyle (FAP). For instance, if your FAP is 1:30 and an interval calls for 5x 100 free at FAP + :15, your pace for the set is 1:45. If you’re fortunate enough to swim in a long course pool all winter just add 15 seconds to every interval.

No Minds

“No Minds” are horrible, painful and completely joyless. Nonetheless, this set is a great way to gauge your swim fitness and to boost your lactate threshold. The set is quite simple to do, but if it’s done right, your arms should feel like Jell-O afterward.

After an easy warm-up of about 1,000 yards, do 5x 50-yards freestyle at race pace to pick your heart rate up. The main set is 5x 100-freestyle on a 4-minute interval. Sure, it sounds easy, but the goal of the set is to sprint all five repeats. Your leg and arm muscles should be on fire at the end of each 100. You should focus on completing each repeat as fast as possible—do not hold back so that you have something left for the next repeat. If done correctly, each successive 100 should be slower (and harder) than the previous one.

Record your time for each 100 and then compute the average pace afterward. We recommend performing this set once every three weeks, and, of course, your goal should be to improve on your average pace each time around.

RELATED: How to Prepare For Optimal Swim Workouts

Mass Start 100s

This set can be done solo, but to achieve the desired effect, it’s best to do with a partner. The focus is to train your body to settle into a comfortable rhythm after sprinting for position at the start of a race. Start by splitting a lane with a swimmer of similar ability. Starting at the same time, have you and your lane-mate sprint 25 yards at an almost-all-out pace. Once you hit the wall go right into a 50-yard swim at slightly slower than race pace. Immediately do one more length, building into a sprint finish. So, the four lengths of each 100 should be done as sprint, cruise, cruise, build. Try 8x 100 yards (freestyle, of course) on a FAP + :30 interval. Try this set whenever you need to add some fun to the doldrums of the pool.

Olympic-Distance Special

Most triathletes we know rarely swim more than 200 yards without stopping, which isn’t exactly the best way to train for a swim of between 750 meters to 2.4 miles. This set is about as boring as they come, but as any fast swimmer will tell you, boring sets are a must-do. The goal of this set is to maintain form and rhythm as your body creeps closer and closer to lactate threshold. After an easy warm-up of at least 800 yards, perform the following set (all intervals are freestyle):

• 1x 500 @ FAP + :5 (e.g., a swimmer with a FAP of 1:30 would have a 7:55  interval)
• 1x 400 @ FAP (e.g., a swimmer with a FAP of 1:30 would have a 6:00 interval)
• 1x 300 @ FAP – :5 (e.g., a swimmer with a FAP of 1:30 would have a 4:15 interval)
• 1x 200 @ FAP – :10 (e.g., a swimmer with a FAP of 1:30 would have a 2:40 interval)
• 1x 100 @ FAP – :20 (e.g., a swimmer with a FAP of 1:30 should aim to complete the 100 in 1:10 or faster)

RELATED: Triathlon Training Plan: Break 2:30 at the Olympic Distance

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Indoor Bike Workouts for Triathletes

These workouts can be done on any indoor cycling set-up that works for you, be it your triathlon bike mounted on a trainer, a spin bike, or a high-end dedicated indoor bike trainer.

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Tabata Intervals

Named after Japanese exercise physiologist Izumi Tabata, this brutal interval set is the most time-efficient cycling fitness builder ever created. Warm up with at least five minutes of easy spinning. Next, increase the tension or gear ratio and sprint for 20 seconds. Now stop and rest passively for 10 seconds. Complete eight all-out sprints of 20 seconds followed by 10-second passive rests. If you’ve done the workout right and held nothing back in those short intervals, you will find yourself breathing harder than you ever have in your entire life after the eighth and last sprint. A cool-down of easy spinning is optional.

In one study, a period of Tabata training increased the VO2max of trained athletes by 14 percent and their anaerobic capacity by a whopping 28%.

DIY Lactate Threshold Test

The lactate threshold is the exercise intensity at which lactate, a secondary muscle fuel, begins to accumulate rapidly in the blood because it’s being produced faster than it’s being used. Exercise scientists argue constantly over the definition and meaning of the lactate threshold, but one thing is certain: It is a very powerful predictor of endurance performance.

In clinical environments, the lactate threshold is determined through a graded exercise test (a workout in which the intensity increases incrementally every few minutes) combined with blood draws. Typically, the intensity level at which the blood lactate concentration reaches 4 mmol/L is marked as the lactate threshold.

Some coaches, including Troy Jacobson, believe it’s possible for athletes to find their lactate threshold on their own with a functional test requiring no needle pricks. According to Jacobson, in trained athletes, lactate threshold intensity is roughly the highest intensity that can be sustained for 60 minutes. Since going all-out for 60 minutes is one killer workout, Jacobson instead uses a 20-minute max effort that is then adjusted to estimate the result of a 60-minute effort.

Hop on your indoor bike trainer and begin with a gentle warm-up of 10-15 minutes. To determine your lactate threshold power, you will need to use a trainer with a built-in power meter. If you want to know your lactate threshold heart rate, wear a heart rate monitor. After completing your warm-up, run or ride as fast as you can for 20 minutes. Be sure to pace yourself so that you aren’t forced to slow down before 20 minutes due to fatigue. Finally, cool down for at least five minutes.

Note your average power output and/or heart rate for the 20-minute max effort. Adjust these numbers downward by 5% to determine your lactate threshold numbers. For example, if your average heart rate in the test was 179 bpm, your lactate threshold heart rate is approximately (179 x 0.95 =) 170 bpm.

“This is a repeatable benchmark test that any conditioned athlete can perform every six to eight weeks to assess changes in fitness,” says Jacobson.

RELATED: Dear Coach: What is Lactate Threshold?

Wattage Hold

Most interval workouts feature intervals of a designated duration. This one doesn’t. Instead, the wattage hold workout requires that you select a certain wattage number and hold it as long as you can, or at least longer than you did the last time you did the workout. As fitness improves, the capacity to sustain very high submaximal intensities increases more than the speed that can be sustained for any given period of time, so the wattage hold is a better way to observe your progress and gain the confidence boost that comes with evidence of progress. And because it always terminates with a cry of “Mercy!” the wattage hold is also a great way to build mental toughness.

To do this workout, select a wattage that you believe you could sustain for a maximum duration of approximately five minutes. Ride easy for 30 to 60 minutes and then increase your intensity to the designated level. Hold it until you are pretty sure you could not sustain it for another full minute and then stop at a round minute number. For example, if after sustaining your target wattage for five minutes you are pretty certain you could not reach six minutes, stop at five. Wait two to three weeks to do the workout again and aim for six minutes at the same wattage, and so forth.

RELATED: Can You Train for an Ironman Entirely Indoors? (Hint: Yes)

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Indoor Run Workouts for Triathletes

There’s nothing wrong with doing steady, moderate-intensity base runs on a treadmill, and in fact if you run indoors frequently over the winter, most of those runs should take this form. But you’ll also want to mix in some more interesting workouts, such as these three.

Steep Uphill Walk

In an interesting study, researchers placed subjects on a treadmill and asked them to walk or run and then gradually increased the incline. They found that at very steep inclines, the biomechanics of walking and running become indistinguishable. Essentially, walking at high intensity on a steep gradient is running, except that the impact forces are much lower than they are in level-ground running. For this reason, steep uphill walking makes a great recovery run. By walking for 20 to 40 minutes at a comfortable intensity on a 12-15 percent treadmill gradient, you get neuromuscular running practice without much impact, so that your muscles and joins can recover from previous running. Try it.

Marathon-Pace Run

Runners and triathletes are often taught to obey the “hard-easy rule” in training. This rule stipulates that run workouts should either be very hard (say, 5 x 1000m at 5K race pace with 2:00 jog recoveries) or very easy (say, six miles at a pace that allows you to hold a normal conversation without getting winded). It’s true that this rule is helpful to the many runners and triathletes who, without it, fall into the trap of monotonous gray-zone training, where they feel compelled to make every run count, so they never go easy—–yet precisely because they never go easy, they are also never able to go very hard.

But there is a place for moderately hard workouts, and the marathon-pace run is a good one. Warm up with one mile of easy jogging and then run anywhere from four to 12 miles (depending on where you are in the training process) at your ideal marathon pace. Doing this workout on a treadmill enables you to lock right on to that pace and stay there.

RELATED: 10 Treadmill Workouts for Triathletes

VO2 Max Test

The workout format the exercise physiologists commonly use to determine VO2max is also useful as a powerful (if painful) fitness-boosting workout. Start by hopping on the treadmill and running easy for five to 10 minutes. Next, increase the belt speed by 0.5 mph and run for one minute at that speed. Now increase the belt speed by another 0.5 mph, hold the new speed for another minute, and continue in this fashion until you feel unable to run any faster. Reduce the belt speed and cool down. Note the maximum speed you attained and try to beat it when you repeat the workout in three or four weeks.

RELATED: Six Swim, Bike, Run Workouts to Increase Your Vo2 Max

This article originally appeared in the January 2010 issue of Triathlete magazine.