TrainingSTRENGTHENING EXERCISES– DO THEY IMPROVE PERFORMANCE?

FasterSkier FasterSkierOctober 10, 2003

This article is the first of three articles examining strengthening exercises for skiers.

Strengthening exercises are advocated for most sports including cross country skiing. The logic is that cross country skiers need to improve power to help increase ski velocity. Power is important as roughly 50% of race time is spent on uphills. The best way to improve power is through both endurance and resistive exercises. Strength training is a great way to provide resistance and gain power. Therefore skiers should use resistance training. However, does weight training improve ski performance? If it does which exercises should an athlete perform, how often and how many. Can power and strength be developed without sacrificing endurance? Unfortunately with most questions this is not easily answered as most of the information is based on anecdotal evidence, the research that has been performed is minimal leaves many questions unanswered. In this article I would like to briefly review the information available.

PHYSIOLOGY
A basic principle in muscle physiology is that to improve performance a muscle must be trained with movements as close as possible to the desired movement or skill (McCardle et al). In other words muscles that are trained in a particular range of motion and/or angle will show the greatest strength improvement in that range, – this is termed angle-specific training.

Improvements in a muscles force production with strength training are related to;
1) Psychological Factors: research has demonstrated improvements in strength can be achieved with appropriate arousal levels, concentration, etc.
2) Muscular Factors
A) Muscle Hypertrophy – resistance training will result in hypertrophy of muscle fibers which in turn help generate tension
B) Muscle Fiber composition – the latest research supports that the percentage of slow to fast twitch fiber composition is static through life. There does appear to be one type of muscle fiber that has both slow and fast twitch qualities. These muscle fiber types can somewhat adapt to either slow or fast twitch based on the demands place upon them. What is more important here is that muscle fibers will increase their strength in relation to the demands placed upon them with training. Slow repetitions will train the muscle fibers to contract slowly whereas fast repetitions will train the muscle fibers to contract slowly. Again specificity is key. It is thought that fast twitch muscle fibers have a greater ability to improve their force generating properties than slow twitch muscle fibers. On the other hand slow twitch muscle fibers have a greater proportion of the cells that allow the muscle fiber to work aerobically. Focusing only on high load exercises is thought to provide greater develop of the force generating properties at the expense of the endurance properties. The opposite is thought to be true of endurance training.

3) Neuromuscular Factors- the initial strength gains noticed in strength training programs are largely related to improved neural organization and motor unit recruitment. I.e. the brain gets better at organizing the muscles needed for strength performance. This is a very important point to remember that again specificity is crucial; skiers don’t really need to get good at doing leg extensions. Doing leg extensions does not necessarily translate into improved ski technique. Restated, performing a certain exercises allows the body to organize the firing of motor-units to provide power for that exercise. This may not carry over into an individual skill.

4) Energy Pathways – (from McCardle, Katch and Katch) Different training will determine which of the bodies energy systems are used. For exercise of short duration i.e. the 100m sprint or power lift the body will use the energy already stored in the muscle these are termed ATP and CP. For short duration exercise less than 2 minutes the body will rely on the anaerobic glycolysis reaction. Beyond 2 minutes the body will increasingly rely on the aerobic system for energy. These energy pathways are also trained depending the demands place upon the body.

RESEARCH
I have included a few research articles briefly summarized and criticized, this is by no means a comprehensive review.
Research has shown that upper extremity power relates to ski velocity in both elite and sub-elite cross country skiers. Hoff et al researched strength training using a pull down motion similar to double poling on a cable machine. The subjects performed 3 sets of 5 repetitions with 2-3 minutes rest between sets at 85% of one repetition max (1RM). The load was constantly increased so that the athlete could do no more than the 5 repetitions, emphasizing explosive performance. The researchers found that skiers who utilized this form of training made a significant increase in double poling endurance, 1RM strength and time to peak work force. No decrease in VO2 max or threshold was found This study was small with only 19 subjects, but did include a control group. The key here is that the researchers used a strengthening device to closely simulate double poling and emphasized explosive power not slow repetitions. The researcher theorized that this type of training will help develop faster nerve reactions. Remember that this study was only carried out for 8 weeks and no longer follow-up was performed i.e. were the gains maintained, and if so for how long? How soon would the strength begin to diminish once the training was completed? This style of training was only studied in the upper body and may not be applicable to the lower extremity. With only 8 weeks of training it would be expected to see strength gains primarily related to increased motor unit recruitment rather than muscular hypertrophy as the authors concluded.

One other study on skiers done by Paavolainen et al examined a combination of strength and endurance training on aerobic and neuromuscular performance. The study was conducted over 6 weeks for 6-9 sessions per week. Seven skiers used 34-42% explosive training (i.e. plyometrics type exercises and 80% of 1RM max squats) as well as 66-58% endurance training. The control group of eight skiers used 85% endurance and 15% endurance type strength exercises i.e. higher repetition arm and leg exercises. The researchers found no decrease in V02 max in the explosive strength group. The researchers found that the explosive group in jump height and in time to develop rapid isometric power. An interesting analysis is made by Hawley in an article on strength training which can be found on the sportsci.org website. He feels that these improvements are meaningless as skiers don’t need rapid isometric force production or the ability to jump high. This is a good point, meaning that the research shows that power can be increased but is it specific to skiing? The research would be more applicable if an improvement was demonstrated in a ski specific activity.

A recent study by Miller et al on triathletes found that combination of endurance training and resistance training improved running economy, hopping power and strength compared to endurance training alone. Similar to the Hoff study the resistance exercises were performed with 3-5 reps at >90% of 1RM max 2 times a week.

Other research in other endurance based sports such as cycling and running has shown that strength training does not interfere with endurance activities. Hawley on the other hand reviews 3 other non-ski research articles examining strength and endurance training. Cycling, swimming and rowing were studied. These three articles do not support the use of strength training finding it detrimental to endurance capabilities. Two further articles he reviewed did find positive benefits, however they used minimally trained subjects. Minimally trained subjects should show improvement with any form of exercise. Hawley concludes that “highly trained athletes who are already capable or generating high power outputs in their chosen discipline, further improvements in strength are a less important factor in enhanced endurance performance…modern training studies do not support the use of resistance training programs for improving the performance of highly-trained athletes”.

However, Hawley may not be familiar with modern ski racing. Skiing is and always will be an endurance based sport. However skiing is increasingly becoming a power-endurance sport. As previously mentioned a typical race involves 50% of the time spent on an uphill. The steeper the uphill the more power required. Modern ski racing will increasingly require power for mass starts, sprints (both as an event and at the end of mass starts races), sprint relays, and uphills.

Ross McKinnon is a former national level ski racer who now competes locally. Ross is a physiotherapist at Rutland Physical Therapy in Kelowna, BC. His interests include improving an athlete’s performance through the use of specific exercise. Ross provides individual evaluations to help improve performance and prevent injury.
For further questions he can be contacted at rcmckinnon at hotmail.com or at 250-765-2665.

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