You can enjoy cross-country skiing if you simply grab a pair of skis and go, but you’ll enjoy it more if you condition yourself first!
Cross-country skiing may be highly dependent on strong leg muscles and strong arm action, but overall conditioning is a definite requirement. If you run, walk, bike, or swim, for example, that will provide you with an aerobic (cardio) base. This is a start, but you also need to strengthen your upper body, specifically those muscles that you’ll use to push yourself along the trail with your poles.
Strengthen your central core, and you’ll be better able to maintain good form at the end of a day of skiing. Lower-body strengthening exercises, especially lunges, will strengthen those muscles that you’ll need to propel yourself forward, and are doubly important for strengthening those muscles that surround that ever-so-important knee joint.
Building a routine that burns calories, increases metabolism and targets muscles important for skiing is important both pre-season and in season. “Circuit training” is a great way to combine cardio and strength if you are short on time. At the same time you will be achieving functional training, which is based on one simple idea: working the body as a chain. After all, the movements we perform each day (sitting, standing, walking, lifting, reaching) all require the firing of multiple muscles. So, why not make your ski conditioning and training more functional and effective by performing more dynamic, compound movements? These compound exercises not only help with strengthening the muscles; they work on your balance, your stabilizing muscles, and the all-important core muscles.

Here’s an example of a circuit to do at home:

Beginner: Do just the first 6 exercises, and work up to all 12.
Intermediate: Do all 12 exercises. As your fitness improves, work your way through it a second time.
Advanced: Do the circuit twice, working up to 3 times through (or more!)

Cross-country-ski conditioning circuit:

1. Squat against wall: Place an exercise ball behind the back and against the wall with feet hip-width apart, abs pulled in and torso straight. Bend knees and lower until knees are at 90 degrees (don’t go down this low if you have knee problems). Repeat this movement for 30-60 seconds. If you do not own an exercise ball, try a basketball, volleyball or child’s ball (I wouldn’t recommend a beach ball

2. Skipping (with or without a rope): Jump with both feet no more than one inch off the floor. If you are not keen on any impact, move up and down on your toes, but still move your arms as though you are skipping. Continue this for 30-60 seconds.

3. Split squat with arm swings: Stand in split stance, right foot in front. Bend the knees and lower the body into a lunging position, keeping the right knee behind the toes (torso upright and abs pulled in). As you lower yourself, swing your left arm forward, right arm back, and swing them back as you straighten your legs (the same arm motion you use to ski). Continue for 30 seconds. Repeat on other side.

4. Jog /march in place: Jog for 15 seconds. Pick up pace for 30 seconds, ease off for 30 seconds, and repeat twice more.

5. Push-ups: From knees, toes or lying on an exercise ball, keep your back straight and abs pulled in while you move yourself up and down for 30-60 seconds.

6. Squat with front kick: With feet no greater than shoulder width apart, lower yourself into a squat, keeping your knees behind your toes (abs in and torso straight). Hold your hands up at chest height, with elbows in. As you rise up, kick with left leg. Repeat with the other leg. Continue for 1-3 minutes.

7. Squat with lateral raise: Lifts your arms from sides out to shoulder height as you lower yourself into a squat. Lower arms as you stand up. Repeat for 30-60 seconds.

8. Side-to-side jump: Place something on the floor. Jump from side to side over the object, landing with knees bent, abs in. 20-30 seconds. For less impact, use alternate side-stepping.

9. Plank with leg extension: Elbows or hands on the floor and toes on the floor. Keep abs pulled in and back and hamstrings taut. Lift foot off the floor and lower. Repeat on other side. Alternate for 30 seconds. You can this modify by doing it from knees or on an exercise ball.

10. Skipping: 30-60 seconds. Jump on one foot for half the time, then switch.

11. Lunge with twist: Step right foot forward with hands clasped out straight in front and lower yourself. When right thigh is parallel to floor, twist to the right (looking straight ahead), then twist back to the front. Push off with right foot and stand up. Continue for 20-30 seconds, and repeat on other side.

12. Curl-up: Lying down, place feet on ball or chair, hands beside head and eyes on the ceiling. Slowly curl up, keeping the small of your back in contact with the floor. Lower and repeat for 30-60 seconds.

Note: Weights may be held in many of these exercises for added intensity.