This is Part Three in a series on preparing for the World Masters Cross Country Ski Championships in Klosters Switzerland March 2017. Part One gives an overview of the training program and Part Two puts structure upon the fundamental approach. Here in Part Three the strength training portion of the program is outlined.
Strength training for cross country skiing is of critical importance for any athlete that wants to perform at a high level. The development and maintenance of excellent technique, increases in power, fast start capacity, sprinting ability, double pole excellence, and many other important aspects of cross country ski racing are all highly dependent on execution of a well-designed strength training program. Yet the singular activity that typically takes a back seat in a masters competitor’s training program is strength training. Strength training should be central to a training program- year round.
It is impossible to have even good (let alone excellent) technique with out the requisite upper-body and core strength. Collapsing cores and flailing arms prevent proper body position, reduce developed power, and lead to highly diminished efficiency in any cross country skiing technique- classic and skate. It is commonplace to see skiers who are spending significant time and money in clinics and individual lessons with “experts” to improve their technique when their lack of upper-body and core strength prevents them from making any improvements. When I teach anyone, I first evaluate where they are by skiing with and watching them for a 5-10 km loop with hills. It becomes immediately obvious if there are any strength issues, and, in my experience, for an overwhelming majority there are significant strength deficiencies. Any technique teaching in such instances is of minimal or no value to the skier. Rather I suggest that the skier embark on an intensive strength program and then resume lessons thereafter. Repetition of technique drills with insufficient upper-body and core strength only leads to increasingly bad technique whereas the same drills performed with well-developed upper-body and core strength allows the skier to “feel” how proper technique results in substantial power and optimal efficiency. This developed “feel” empowers the skier to refine their technique every time they ski utilizing a power and efficiency feedback loop that is essential for tweaking one’s technique. No coach or teacher can be there all the time and it is critical that one develop this “feel” in order to facilitate continuous improvement. But it all starts with upper-body and core strength.
Strength training is the foundation of good cross country skiing technique.
synchrony- the most important aspect to strength training
When working on strength development for a sport it is important to realize that strength increases are most effective when they translate directly to the whole-body motions involved with the particular sport at hand. This is most efficiently and effectively accomplished when the exercises themselves replicate the positions and timing required in the sport. For cross country skiing this means that all strength exercises should involve whole-body motions that connect the upper body group with the lower body group through the core. This is because all motions involved with good cross country skiing techniques simultaneously recruit all three of these muscle groups (motor units) and the highest levels of power can only be attained when the full set of necessary muscle groups are used in synchrony. In practical terms, it does not actually matter how strong each individual muscle group is if they cannot act together, in a sychronous way, to translate that strength to delivered power on skis.
"As we hope you can see by now, strength is the basis of endurance."
Steve House and Scott Johnston in "Training for the New Alpinisim" p.144
This developed muscle group synchrony perhaps has the greatest effect on endurance- yes, endurance. Studies of high-level cross country skiers have shown that time to exhaustion in a double poling exercise can be increased by as much as 100% through a nine week program of 30 minutes per week of maximum strength training. The operative theory behind such improvements is that engagement in a well designed maximum strength training protocol will allow the athlete to develop the ability to draw upon an increasing pool of motor units that can be routinely accessed during training and competition. It is a neuro-muscular adaptation that gets “wired” into your system (and psyche) and becomes the basis for increases in endurance.
Strength training is the foundation for cross country skiing endurance.
Strength exercises that involve whole-body motions that are similar to (or, preferably, exactly like) those in good cross country skiing technique are by far the best exercises to focus on. The neuro-muscular adaptations alone, even with just small strength increases, are sufficiently important that even marginally challenging exercises that map well onto cross country skiing will lead to major improvements in skiing power and efficiency. Add some challenging weight to the equation and you have a recipe for getting the most out of your ageing body.
An excellent source for information on strength training is the book “Training for the New Alpinisim” by House and Johnston. Scott Johnston has been a coach for numerous US Cross Country Skiing Olympians over the past decade. The strength training portions of his book, although pointed toward the demands of alpine climbing, are directly applicable, with minor modifications, to cross country skiing. I highly recommend that you read this book as it is a great guide not only for strength training but also for cardio aspects as well. All of Chapters 4 and 5 and portions of Chapters 7 and 8 are of great value to understanding the physiologic basis for strength training for endurance sport, the types of strength exercises an endurance athlete should be doing, and for guidance in designing a personal strength training program. I have modeled my own program around Johnston’s general guidelines.
Here are a few examples of exercises that Johnston put up on video a few years ago that use the “whole body synchrony” principle with simple equipment in a non-gym environment:
In this video you are watching two US Olympians, a guy who spent time “on the bubble” of US Team status, and the ageing coach all engaging with simple, whole-body motions that map well onto good cross country skiing technique (with the exception of the punching bag, IMO). Use this type of program as a conceptual template, develop a program that fits your needs/situation, and you will likely see significant improvement in your skiing and ski racing.
In summary, the two guiding principles for making strength training a core part of your cross country skiing training program are:
- Strength training is the foundation of good cross country skiing technique.
- Strength training is the foundation for cross country skiing endurance.
the primal importance of double poling
As a result of a focus on strength training by World Cup athletes and the many equipment improvements that have taken place over the last decade, double poling has become a more and more important part of the sport. Efficient and powerful double poling as seen in World Cup competition is a direct consequence of rigorous, highly challenging strength programs that are currently in place with all of the competitive national teams. As mentioned previously, this focus on strength has resulted in an increasing number of competitors choosing to go waxless and double pole entire FIS homologated classic races- sometimes to victory. Although many lament the potential demise of the classic stride technique, no sport will survive if innovation and progress is squelched. I assert that double pole technique is the future of the sport and that further technique development (both classic and skate) will be partly due to the result of improved double pole technique and the associated upper body and core strength that is critical to any powerful and efficient double poling movement.
An uphill double poling interval session- perfect training to enhance your classic (and skate) skiing competitiveness.
For the masters competitor the single most important technique and ability improvement that will result in the largest improvements in competition is the double pole. Just look at the start of any masters classic race and you will see those competitors that will be winning their respective age groups are leaving the rest of the field in the dust by efficiently and powerfully double poling away and up to a racing pace and stride frequency in a faction of the time of other competitors. Add to this the fact that the V2 poling motion is essentially a double pole motion, and the same thing occurs in skate races. Improve your double pole and you will quickly become much more competitive.
"...my personal goal is to become one of the best double-polers in the
world, I needed to learn from the best"
Andy Newell, US Cross Country Ski Team Member, on his 2016-2017 goals
Since a powerful and efficient double pole is entirely dependent on upper body and core strength, any masters competitor should be prioritizing a strength program specifically aimed at improving double poling ability. From improved double poling capacity will flow improvements across the spectrum of abilities needed for being competitive in cross country skiing races.
strength training for masters cross country skiers
Let’s revisit the “Big 3” physiologic challenges for the masters endurance athlete covered in previous posts:
- loss of muscle
- decreased aerobic capacity
- increased body fat
Arguments have been previously presented that support the ordinal listing above as most applicable to masters cross country skiing- meaning that the number one issue that we, as masters cross country skiing athletes, need to attend to is loss of muscle. This can only be sufficiently addressed with a well-designed strength training program and a detailed plan for execution. Such a program should ideally be developed with a professional that understands the unique demands of cross country skiing. It is not straightforward to find such an expert in strength training for cross country skiing as even many of those who claim to be “experts” actually aren’t.
One source for information is this fellow who has quite a bit of experience specifically with training cross country skiers at the highest level. A couple of resources that he has recently made available on the web are:
Introduction to Strength Training for Cross Country Skiing
Detailed Strength Program and Downloads Including an Excel Spreadsheet
But do not let the lack of a strength coach, strength professional, or other “expert” prevent you from developing your own program. The basic concepts are not complex and a reasonable amount of research and experimentation should allow for the development of a safe and effective personal program that one can have confidence in.
As in any training program, and particularly in a strength program, you should be very careful about what you do as one’s individual needs and abilities are unique. This is where the guidance of a professional can be valuable. What is described here is what works for me and I do not necessarily recommend any of these exercises for everyone; the intent is to outline a strength program example- not a prescription or recommendation.
a simple strength program
If you are like me, you probably do not like gyms. I find gyms to be expensive, inconvenient, inflexible, and full of germs. I also tire very quickly of having to ask some Millennial to get off of a piece of equipment I want to use and to go “text” somewhere else. And then there is the music… enough said and enough GOM* talk…
It is simple to set up a home gym for cross country skiing-specific strength training in either a garage, a basement, or a shed. You do not need a lot of room, just a few simple pieces of equipment and some motivation.
A basic operative premise is that any strength exercise should map as closely as possible onto the whole-body movements in cross country skiing. As reviewed above, isolated working of muscle groups, while perhaps required for full development, do not activate the very important neuro-muscular adaptations that are key to powerful and efficient cross country skiing and endurance. Synchrony is “King” and your strength program should be designed around ensuring that proper muscle group synchrony is developed.
The other important aspect of strength training for cross country skiing is the development of maximum strength that will, in time, translate to muscular endurance and power delivery on skis. Here again, synchrony plays a central role and addressing a maximum strength improvement program is one of the largest levers one has with respect to significantly increased power and endurance on snow. Johnston has this type of work integrated into his strength training programs and they are nicely outlined in his book and directly applicable, with appropriate modification, to cross country skiing strength training.
a core group of functional exercises for a year-round strength program
The following are some exercises that I find to be functional. These do not form a complete matrix but rather they represent a portion of a core set of exercises that I engage in year-round and that are augmented with additional work at various points in the year. This group hits all of the basic muscle groups in a way that is specific to cross country skiing; they also do not require much of an investment in equipment.
- Weighted pull ups– this is a key exercise that, in the right progression, will quickly and safely allow one to attain a maximum strength goal.
Buy a pull up bar and mount it your garage/basement/shed.
Buy a weight vest and use it to provide increasing resistance as you proceed through a progressive program of overhand pull ups. Johnston gives an example of such a program (he calls it a “Special Max Strength Plan” on page 228) as follows:
2 sessions per week
adjust the load so that you can only just do the required number of repeats
This is an eight week plan that I accelerated to five weeks without issues, but that is for me and I do not recommend it. You will see from the table that the program involves escalating total work with a couple of level weeks to allow your body to catch up to the stimulus. The rest time after each set is needed to allow for best efforts but it also allows one to include this work in a circuit program of alternating muscle group focus. You will be amazed at how much weight (as measured by percent of body weight) you can load into your weight vest by the end of this sequence. After the terminal session I maintain this exercise in the circuit program at the 3 sets of 3 reps at the terminal vest weight throughout the race and off season. The following year I go through the build progression again adding additional weight to a new plateau and then maintain that new, higher, level through the race and off season. I am now entering the third year of using this protocol and have yet to totally plateau out but at some point I am sure I will. You might think that such weighted pull ups are an upper body intensive exercise but you will find that in order to complete the pull ups you will be using all the major muscle groups including the core and leg muscle groups. Force generation in the pull up exercise requires synchronous recruitment from all three major muscle groups in way very similar to what one does in a good double pole motion and this is why this exercise is such a good one for cross country skiers.
Here is a general source for information on weighted pull ups- it is targeted to weightlifters but there is some good information on how much vest weight you should be working toward as well as some technique tips.
- Weighted Step-ups– while you still have the weight vest on do a set of step-ups
Buy an adjustable work out step device
With the weight vest on step up onto the platform with one foot and balance (make sure the step is not too tall, otherwise you will be loading your knees in a position that is dissimilar to skiing). Then step down and return both feet to the ground and then step up with the other foot and balance again. Do as many repeats as you see fit.
- Resistance Band Exercises– for minimal equipment cost one can work upper and lower body muscle groups in a way that recruits the core and simulates cross country skiing-specific body motions
Buy a quiver of resistance bands with a range of elasticity (durometer) and securely mount a robust, properly sized eyelet in a wall at about 12″ above head height and another one about 4″ above ground level. Slip a large carabiner through the eyelet and then slip the elastic part of the resistance band through the gate in the carabiner. Now you can use the resistance bands to do a large variety of exercises. Typical exercises include forward facing pull downs, pull to’s, overhead pull downs, abductor and adductor laterals, among many, many others. You can also use the pull-down exercise combined with a tether around the waist anchored to an opposing wall that allows you to lean forward and pull down just as one does in the double pole in skiing (this is illustrated in the Johnston video where they utilize a pulleyed weight stack on guide poles for resistance). If you have extra money a TRX strap can also be used for these exercises but realize that you need a lot of room to use a TRX strap properly. I also do not like some of the positions that the TRX strap will put you in as they bear no resemblance to cross country skiing. If you have even more money (like about $800) the SkiErg by Concept 2 is a very nice cross country skiing-specific exercise machine. I find that you need to employ a tether with the SkiErg to get the proper poling position and muscle recruitment. Nearly all of the National Teams are now using the SkiErg (or something very similar) in circuit training both with and without tethers.
Other elastic band exercises include the use of a simple elastic band loop that wraps around your ankles which you can then do side steps across a given distance or for a specific number of reps. This is a review of many of the types of exercises you can do with elastic bands.
- Garhammers– some call this exercise a hanging leg lift but it is actually quite different
Going back to the pull-up bar, hang off the bar and bring your legs up flexing at the knees and bringing your knees to your chest and up towards the bar, then fold your legs out parallel to the ground, hold, and then slowly lower your legs down- this is one rep. I add a slightly less than 90 degree lock-off in the arms to mimic the position of the arms during the power portion of the double poling motion to simulate the full body motion used during cross country skiing. What you will feel in this exercise is very much like what you feel when you are double poling on snow with good technique. Here is short video showing the exercise without the 90 degree lock off in the arms:
- Simple push-ups– basic, with feet on the adjustable step (or balance ball), with one arm, picking up one leg, simple with hand weights and picking up one hand weight sequentially per rep, etc., etc., etc.
You can’t get any simpler than push-ups but they provide whole-body movements that have direct relation to cross country skiing.
- Box jumps and/or plyometrics- side-to-side, forward and back, single foot, etc.
These are great exercises for developing explosive power essential for downhill skill development and to initiate accelerations that are often critical for starts and staying with a surging pack in a race. Unfortunately these types of exercises are fairly stressful on connective tissue and joints in general and should be carefully applied for masters skiers. Any knee issues? avoid these. Any developing joint issue? stop doing these. But if you can handle these there is no replacement for them as they uniquely develop explosive power, another thing that masters skiers are loosing at alarming rates. And do not minimize the importance of your downhill skills- for the competitive end of the spectrum, most races are lost on the downhills and without the explosive power needed to execute on difficult downhill turns and fast descents you will be left in the dust wondering about exactly what just happened.
So with just a few hundred dollars and a small space you can put together a “gym” that serves as a highly functional cross country skiing strength development tool. This equipment and the associated exercises make doing the all important strength part of your training program convenient and inexpensive- and hard to skip as you will not have any excuses about no time to make it to the gym or that the gym is closed or crowded.
“real” terrain strength programs
Getting out of the “gym” and onto terra firma and actual cross country skiing-type equipment is critical to translate any strength improvements in the “gym” to the ground or snow. There are three basic pathways to accomplish this:
- Hill bounding with poles
- Mountain running
rollerskiing as strength training
I know this is not conventional thinking, but my experience leaves no doubt: skate and classic stride roller skiing on varying terrain is of minimal use to the master skier. This is because of numerous factors starting with the inherent danger associated with rollerskiing on pavement. A masters skier just cannot afford to go down on the hard pavement given their typical state of connective tissue and bone density. A good friend (and rheumatologist) once put the life of connective tissue and joints like this- you start out as “jello” as an infant, progress to “rubber” through your teens and into your 20’s, then “leather” through to your 40’s, and finally to “glass” at about 50+. We all know what happens to glass when it hits a hard surface! And diving off the road at 25-30 mph in reaction to some random texting driver is not a situation you want to deal with. An entire ski season can be ruined just trying to get in some roller skiing in the summer and fall. I think the danger outweighs the reward for skate and stride roller skiing over varied terrain, even with the currently available (and difficult to use) brakes. “Speed reducers” are a viable option and one you might look into.
The danger, Ms. Randall says, is the (roller) skis don't come with
brakes, and skiers can reach 45 miles per hour on them. "If you have to
stop suddenly, you pretty much have to dive off the road," she says.
"That's why you wear a helmet."
Kikkan Randall interview in The Wall Street Journal 23 May 2012
Another reason not to focus on varied terrain roller skiing is that without continual coaching it is all to common for athletes to develop technique issues. Stride and skate roller skiing is actually not at all similar to on-snow skiing. This is particularly the case for classic striding. Many a skier with good technique has been derailed by too much stride roller skiing with perfect (i.e. not-attainable on-snow) kick only to find that their timing, weighting, and body position have changed for the worse once on snow. It can take some valuable time and effort to get your technique back once you have gone down this rabbit hole.
Finally, rollerskiing, according to long time Sun valley Ski Educational Foundation (SVEF) head coach Rick Kapala, is the first thing that retiring elite-level athletes stop doing. Why? Because of the danger of injury weighed against the training stimulus and “sort-of” ski-like dynamics favors not roller skiing unless it is critical to your success.
As argued earlier, the single most important motion in cross country skiing is the double pole. This is because the double pole is the motion that cuts across both classic and skate technique and it is the motion that, due to technique, strength, and equipment developments, has been enabled as a primary motion for many racers. Masters skiers can most advantageously utilize a well developed double pole to increase their speed and competitiveness in both classic and skate races. Combined with a well planned strength program, double pole technique development will have the greatest impact on your skiing. This is why I advocate for double pole rollerskiing.
Contrary to stride and skate roller skiing, double pole rollerskiing is a reliable surrogate of what one does on-snow. Body position, pole planting, timing, and weight shift in double pole rollerskiing is exactly what you will do on-snow and therefore translates well once the season starts. When done for long distances and/or on uphill grades it is a challenging workout. Double pole rollerskiing is also safe so long as you stay away from steep downhill grades. I stick to 1.5-2% grades and have no issues with control on the downhills.
One approach is to find a 2-3 km 1.5-2% grade uphill on a nicely paved road (such roads can often be found in local low-density US subdivisions with very few (or no) cross streets). Then do repeats on this uphill for whatever length workout you have planned. I typically do 45-90 minutes which involves a lot of repeats, something that may be too “boring” for some. For me, having spent my teens and early 20’s as a competitive tennis player, I find the repetition constructive as it allows one to hone in on the details of the technique and to “feel” the feedback loop that is essential for positive technique development and power generation. Just as hitting 200-300 serves per hour in practicing for tennis is essential to developing a “killer” serve, double poling at 60-90 rpm for 1-1.5 hours is similarly essential for developing a “killer” double pole. The repeats also allow you to measure your progress by using a GPS watch for pace. With some of the newer watches you can also monitor your poling rate, stride length, and ground contact time (stride time). All of these parameters can feed back into helping you develop your double pole technique toward excellence, even without a coach. There are also significant strength and endurance improvements from regular uphill double pole roller skiing that are hard (or impossible) to replicate in the gym.
I will also add a weight vest for additional challenge, something that is becoming more common. Noah Hoffman spotted Sundby one early morning this past season before a 30 km Wolrd Cup classic race double poling uphill with a weight vest- not something that I would recommend for a masters skier before competition but something to possibly include in your dryland and on-snow workouts if you are up to it. The key is to ensure that the added weight does not adversely affect your double pole technique. Any weight should be added very progressively and conservatively. With proper use of a weight vest you can straightforwardly turn a 1.5% grade into a 3% or even 5% grade- and stay safe as well.
Another approach, particularly aimed at muscle synchrony, muscle strength, and muscle endurance, is to find a challenging, long uphill grade and do an uphill-only workout. We have one of these in the Sun Valley area- the climb from Galena Lodge to Galena Pass. This road section was recently repaved and represents a 10 km, 4% grade, 400 m (1300 feet) continuous ascent with a wide, smooth shoulder. This is a challenging higher altitude double pole workout that, at 50-60 minutes duration, takes significant muscle endurance to complete. The altitude ranges from 2250 m (7400 feet) up to 2650 m (8700 feet). Here is the profile:
Elevation profile for the 10 km 400 meter (4% grade) climb from Galena Lodge to Galena Pass in Idaho. A great double pole workout at steady state or threshold.
We do this workout by taking a vehicle and a bike to the top, leaving the vehicle, riding the bike down, and then roller skiing up to get the vehicle. Repeat as desired.
I find uphill roller skiing, specifically double pole roller skiing, to be a great addition to a strength program and one that also uniquely allows for technique development as well.
As far as what roller skis to use for double poling, I will recommend the Swenor Finstep. These roller skis provide a good “snow-like” feel while double poling, great glide, a “Cadillac” ride, and good ground clearance. The Finstep are also durable as I have over 2500 miles on mine and the wheels are just now starting to show wear sufficient to begin thinking about new wheels. These skis are heavy and not recommended for stride skiing unless you want to work on your calf and glute strength. There are many other roller ski options for classic striding, but, as reviewed above, I do not recommend classic stride roller skiing.
Hill bounding, particularly with poles is one of the most effective whole-body exercises you can do as a competitive cross country ski racer. There is much written about hill bounding but the following video by SVSEF and Gold Team Coach Colin Rodgers is about as thorough in 8 minutes as I could be in about 1000 words, i.e. watch the video- it is a great resource for incorporating hill bounding exercises into your training plan. Colin demonstrates on the same hill that we use extensively starting in September where we also include longer (20 minute) aerobic and VO2 max workouts up the cat tracks to the top of the mountain (Dollar Mountain). We are fortunate to have this hill (and mountain) right in our back yard about 5 minutes walk from the front door!
Once again the whole-body, cross country skiing-like motions are central to getting the most out of hill bounding. Cardio, strength, and technique come together in these sessions and they should be a regular part of your training plan.
Mountain Running is the age-old dryland training method used since the Pleistocene when the likes of Bill Koch and Tim Caldwell would load up their day packs with rocks and run up Mount Moosilauke or into the Whites. There is no more enjoyable training session than a 5-6 hour mountain running adventure. The grade determines the pace, the style (i.e. running or speed hiking), and the work. Long distance Mountain Running develops lower body power, aerobic capacity, balance, and foot work (on descents) all of which are central to competitive cross country skiing. It is a great over-distance (OD) training session to do with a group and to discover some mountain areas that you have always wanted to venture into.
US Ski Team members headed out on an afternoon mountain run in Alaska this past July. Photo credit: Sadie Bjornsen link
How much strength training should one do? It’s a big question and one that is entirely individual. Some general guidelines include doing strength focused sessions twice per week for 1-1.5 hours, making sure the work is safely progressive, and to be patient with results. Although you may experience significant improvements in the first few months of strength training, additional increases come more gradually. For the masters skier this process is even slower since both human growth hormone (HGH) and testosterone (T) levels are waning. It is best to have a longer-term horizon of expectation for strength development- more like 18 months than the 9 months when you were a 20-something.
daily stretching – daily strength
It should go without mentioning but I will emphasize the importance of post-workout stretching for anyone who is participating in a rigorous and challenging training regimen. This is especially important for masters skiers whose connective tissue is becoming more and more brittle every day.
Another activity that can help not only with strength development but also with balance is a daily lunge matrix. There are a lot of possibilities here but I have found that the simpler the matrix the more likely one is to consistently do this. Once again the lunges should map onto cross country skiing motions as closely as possible. I do 4-5 different lunge types in 10 reps per leg for three sets daily after the primary workout. Although you will feel these lunges in the activated muscle groups, the real challenge becomes balance- in a way very similar to cross country skiing. The important thing here is the activation of the smaller stabilizer muscles which are critical to good balance and skiing skill. Here is a lunge matrix from Jay Johnson, a well respected running coach. He describes this as a warm-up matrix but I use it as a stand alone post-workout daily strength/balance routine (with the exception of the backwards side lunge as this exercise bears no similarity to any motion or position that one will be in while cross country skiing). You can also add weight to any of these lunges for additional challenge.
And a final daily exercise is the simple (though difficult for some) act of putting your socks on (or taking them off) without leaning against or holding on to something. Give it a try and you will discover what balance is all about. Do the same when you put your running shoes on and continue by tying them without stepping down. These are good balance/strength challenges that focus on the smaller stabilizer muscles- and they can naturally and consistently be done on a daily basis.
Strength training for masters cross country ski racers is unique in that we need to concentrate on the elements of our physiology that are diminishing at the greatest rate and that are having the largest negative impact on our speed and competitiveness. These primary elements are loss of muscle, diminished aerobic capacity, and increased body fat. Strength training focuses on muscle loss and it is critical that we put sufficient emphasis on strength training so as to slow down or stop or, hopefully, reverse any muscle loss that we have experienced. Add to this that it is impossible to execute good skiing technique without sufficient upper body and core strength and it becomes clear that strength training should be a very high priority in your training plan.
A few approaches to strength training for cross country skiing have been outlined. They all center around exercises that map well onto the whole-body motions involved in cross country skiing. This allows for targeting of the most important muscle groups but, also, to help develop the necessary muscle synchrony (neuro-muscular adaptations) to best achieve maximal power, efficiency, and endurance.
I will again encourage you to read the book “Training for the New Alpinisim” by House and Johnston as it provides a most thorough and insightful basis behind, and exercises for, successful strength training for endurance athletes.
*GOM = Grumpy Old Man