Muscle Cramping, DOMS and endurance events

Cramping and delayed onset muscle soreness (DOMS) are frequent complaints of novice and elite endurance athletes.

Professional cycling

• 80-120 race days
• 27,000 - 39,000km/yr
• Tour de France 3 week race can be lost by 3 minutes, a fraction of the overall time
• In the pelliton they consume on average 200W @ 40km/hr and uphill approx 400w
• 26 cheese burgers is the calorific equivelent for 1 days racing (approx 9000Kcal)
• Sweat rate approx 1 litre/hr
• Average fluid loss 2.1litres +/- 0.6litres (in cooler months)
• Occasionally in the Tour de France fulid loss is of the magnitude of 4litres
• Percentage body fat of profesional cyclists is 3-6%
• Flat terraine Oxygen consumption of 5.5 -> 7 l.min
• In the pelliton there is a decrease of 40% of oxygen consumption
• Dehydration can reduce strike volume by 28% thereby significantly reducing cardiac output as the 13% increase in heart rate isn't enough to compensate. The reduction in blood pressure also leads to reduced muscle perfusion
• 1g of carbohydrate combines with 1g water, therefore adquate fluid consumption is required for carbohydrate loading
• Pre exercise carbohydrate loading combined with carbohydrate-protein supplementation immediately and up to 4 hours after exercise may reduce the release of stress hormones and hereby reduce immune function compromise
• Anti-oxidants should reduce post exercise inflammatory response by 'mopping up' oxygen free radicals
• There appears to be an increased incidence of retro-lymphatic malignancies in endurance athletes
• If doing repeated bouts of exercise, a 3 to 6 hour recovery may be enough time to re-establish post-immune depression to acceptable levels
• Adipose tissue triglycerides can provide 50 000 - 100 000 Kcals, whereas the liver glycogen can only provide energy of 200 - 400 Kcals

• Caffeine consumption may improve contractile activity, improve concentration as well as aid the mobilisation of free fatty acids. However, excessive consumption may cause anxiety and dehydration.

Causes of cramping are multifactorial and theories have included an ion imbalance of magnesium and potassium, lack of energy, reduced blood flow, poor diet, and inadequate training when preparing for an event.

Endurance athlete investigations using magnesium as the mechanism of cramping is based on the fact that i.e. intracellular (sarcoplasm), as well as the central nervous system. Since magnesium acts as the antithesis of calcium it may prevent leakage of calcium into the sarcoplasmic reticulum as well as aiding the muscles relaxation phase after each and every nerve impulse. At a central nervous system level, it acts in the wide dynamic range neurones which are responsible for the modulation of pain impulses.  Sodium and potassium on the other hand reside in the muscle membrane and are involved in the ionic depolorisation of the membrane, which then leads to the release of calcium from the sarcoplasmic reticulum.  The quinine in tonic water may aid in the stabilisation of this membrane, however electrolytes still need to be present. With water intoxication the thought is that the sodium concentration has been diluted down from too much water.  

Another mechanism of cramping may be the lack of ATP - the energy substrate required for the release of the contraction between the myofilaments (see end of   endurance_training). The natural state for a muscle is contraction e.g. 'rigor mortice', and energy releases the contraction to allow shortening and lengthening of the muscle.  Inadequate release of the muscle during the eccentric (muscle lengthening) phase of contraction can lead to broadening and streaming of the 'Z-bands' and thereby the loss of muscle structural integrity. This is thought to lead to DOMS, which can take a muscle up to 28 days to recover from.  Additionally, the aforementioned Sodium-Potassium ionic membrane channels require energy in the form of ATP. Carbohydrate loading prior to an event is also a commonly used strategy to prevent fatigue and thus cramping.

Lactic acid has been traditionally blamed for the loss of performance.  However, lactate is used by endurance athletes to produce pyruvate in the liver, thus supplying the system with energy.  There is even data to suggest that lactic acid is produced and used at rest for energy supplies.  Dr Toni Held demonstrated that over 50% of elite orienteers cognitive abilities in map, object and spatial recognition improved when exercising above anaerobic threshold.  This is unfortunately unpublished data as the conventional 'wisdom' and group think at the time (1986) didn't feel that this was conceivable!!! Therefore, lactate may not be as bad as people suggest and I personally remember thriving on lactate when I was really fit and competing at orienteering in Europe. 

Importantly, these reactions require adequate blood flow for the transportation of energy to the sites of contraction as well as removal of metabolic byproducts from the contractions. This adequacy includes the maintenance of the blood volume which can be lost through sweat.  Additionally, cardiac output is a product of heart rate x stroke volume. Therefore, if the volume of blood reduces, cardiac output must be compensated by rises in heart rate and/or changes in blood pressure.  The latter being a strong contra-indication to further exercise. It must be remembered that heat exhaustion can be fatal!  However, sweating alone is not the cause of cramping, since even concert musicians can cramp in the absence of profuse sweating.

There is evidence to suggest maintaining blood vessel patency in the form LDL cleansers such as omega-3 and omega-6 free fatty acids may be of value for optimising performance.  Since the metabolic reactions in the muscles produce a high oxygen free radical loading, the use of Vitamin E as an anti-oxidant has also been advocated.  However, a recent publication suggested potential increased risk of heart disease if taking Vit E for prolonged periods (in this case 7 years). People have suggested that the high berry and raw fish (Herrings) diet of the Scandinavians and the root and Sushi diet of the Japanese has contributed to their longevity due to the high anti-oxidant content and cleansing nature of these foods. However, it must also be remembered that these people live in cold climates and their culture propagates participation in regular exercise (e.g. riding the bicycle to work, school and shopping).  Interestingly, Scandinavian populations in North America don't seem to maintain their longevity to the same extent, possibly due to the highly processed nature of those foods and lack of exercise.

Recently, the use of a combination of carbohydrate and protein supplements before, during and after exercise have been advocated.  The theory being that protein can be highly restorative to muscle tissue.  I personally use the Endura products for Creatine, HMB, Magnesium and Carbohydrate-protein supplementation.

Hence, the causes of cramping are multi-factorial. Generally, cramping occurs when muscles are asked to contract beyond their normal nature of exercise. Therefore, diet supplementation is not a substitute for adequate training.  Never-the-less fluid, electrolyte and most importantly energy replacement during a long distance event is essential in the maintenance of performance and prevention of DOMS.  Athletes should consult a sports dietician for specific advice.

Constituents of carbohydrate gel supplements (per serving) commonly used in Australia

Important points to consider

	CHO choice shouldnt impede stomach emptying thus interfering with fluid delivery
	CHO shouldnt cause G.I. problems
	Ideally drinks should contain 4-8 % CHO
	If hunger is a problem, try using real foods such as bananas and breakfast bars instead of supplements such as sports gels
	Variety of foods (both sweet and savoury) important to prevent 'flavour fatigue'

During the 2006 Tour de France, athletes used power output (P=Ft) to determine the pace of their race. Similarly, they calculated energy expenditure (W=Pt) to determine the amount of calories (up to 6000 Kcals) they needed to replace each day. Hereby, the 'tank' shouldn't run dry, nor power output dwindle.

1st Law of thermodynamics : energy in = energy out

If you can estimate the % Vo2 that an athlete is working at, and you know for what period of time they are working at this rate, then you can calculate an estimate of energy need during their event

Preparation

	Ultra-endurance events > 4 hours, normal glycogen stores are inadequate to maintain exercise
	Depletion of CHO stores is a major cause of fatigue during endurance exercise
	CHO loading pre-event may increase glycogen stores by 200%

Carbohydrate Loading

Traditional		Modified
	7-8 days prior to event reduced CHO intake		Maintain normal diet 7 days from event with moderate training; 3 days from event, increase CHO intake significantly (total CHO and as a % of total calories)
	Maintain moderate training for 2-3 days		Very little exercise from this time to event
	Results in glycogen depletion 3-4 days out from event
	During this time Holly would increase CHO intake and reduce activity
	Results in a supercompensation of glycogen stores to very high levels		Still elevates glycogen well above normal training levels
	Problems include fatigue during low CHO phase		Eliminates side effects of low CHO phase of traditional method

Nutritional needs and cramps - a clinical case study of a female triathlete (powerpoint presentation)

Immune Response to Exercise (http://www.nature.com/icb/journal/v78/n5/full/icb200076a.html)

Anti-inflammatory and anti-oxidant effects of Curcumin (http://en.wikipedia.org/wiki/Curcumin)

Exercise and Type 2 Diabetes

as a physiotherapist I suggest that athletes consult a sports dietician for more specific advice.

Last update :10 January 2009