|XII FINA World
Congress on Swimming Medicine, Goteborg, Sweden
Andy M Stewart, Scottish Institute of Sports Medicine and Sports Science, Glasgow, Scotland
Ross H Sanders, Department of Human Movement, Edith Cowan University, Joondalup, Western Australia
Sportscience News Sept-Oct 1997
|Presentations reviewed: Training and Performance · Immunology · Ergogenic Aids and Performance · Altitude · Muscle Fatigue · Tests and Training Prescription · Swimming Technique · Propulsion and Drag · Swimming Injuries|
This year's conference of the world governing body of swimming (Federation Internationale De Nation Amateur or FINA ) was held in beautiful Goteborg, Sweden on April 12-15, 1997. Meetings have been held every two or three years and for the first time, this year's conference was held in conjunction with the World Short Course Swimming Championships. FINA plans to adopt this approach for future conferences as it apparently cuts the costs of getting all members of their Medical Committee together in the same place at the same time - not a bad idea! Over 200 delegates attended the well-organized conference. Summarized below are those papers that we were most interested in. For those of you who are interested in swim research, we hope to see you at the VIII International Symposium on Biomechanics and Medicine in Swimming in Jyvaskyla, Finland, June 28-July 2, 1998.
TRAINING AND PERFORMANCE
A contentious issue in swim training is specificity vs long, slow distance. Stewart, Sanders and Hopkins asked 12 coaches to prescribe a race-specific, high-intensity, low-volume training program for a period of six months, while another 12 coaches in a control group were expected to prescribe training using their usual long, slow program. There was a gain of a few percent for sprinters (50-m and 100-m events) in the race-specific group relative to the controlgroup, and no real difference between the groups for middle-distance swimmers (200-m and 400-m events). But the coaches did not comply well with the training programs, so we still don't know for sure which type of training is better.
Is there a difference between stroke rate and stroke length at various levels of effort? Kohji Wakayoshi presented results from a study investigating the relationship between physiological parameters and stroke technique at aerobic and anaerobic intensities. All tests were conducted over 400 m in which paces equivalent to 80% to 85% of best pace and 90% to 95% best pace were found to be primarily aerobic and anaerobic respectively. The pace equivalent to 85% of VO2 max was found to have a strong affinity to maximal 400 m pace (r=0.978). Swimmers maintained their stroke rate and stroke length while swimming at aerobic intensities, but stroke rate and stroke length increased and decreased respectively during intensities that enduced primarily anaerobic metabolism. Bottom line: train at paces that will increase your ability to maintain the high stroke rate and stroke length required in competition.
There's a fine line between that training load that may lead to optimal adaptations in the immune system and one that leads to immunosuppression. Bente Klarlund Pedersen presented one of the more popular papers at the conference discussing the the "J Curve". Most of us were familiar with this theory: little or no exercise leaves the individual open to some infections, moderate exercise leads to enhanced immune function, while high-intensity exercise leads to immunosupression. But just what is the association between the endocrine and immune system? In essence, stress hormones mediate the changes in the immune system by blocking hormone production and receptors. She reported that athletes should accept that acute immunosuppression is expected and indeed necessary to enhance the chronic immune response, because moderate "doses" of immunosupression would probably lead to a stronger defense system when the athlete engages in periods of heavy training. We asked Dr Pedersen for her opinions on an association between the neuroendocrine system, the immune system, and proteolysis of skeletal muscle, but we were unable to stimulate much discussion on that subject.
ERGOGENIC AIDS AND PERFORMANCE
Priscilla Clarkson gave an update on current opinions on nutritional ergogenic aids, antioxidants, and physical performance. She reported that creatine supplementation was beneficial for repetitive (~2 mins or less) high-intensity exercise bouts (i.e. training or in repetitive competitions that are less than 5 mins apart), but not for one-off sprints. Amino acid supplementation might enhance the action of growth hormone, but diarrhea is a major side effect. Ephedrine has a potential role in weight loss, especially if combined with aspirin. Chromium potentiates the role of insulin to get glucose and amino acids into the muscle, but whether there is an enhancement in performance is not clear. She suggested that chromium supplementation might help athletes who have been on a calorie-restricted diet. Forget magnesium supplementation! Supplementation with vitamins C and E, other antioxidants, or antioxidant mixtures were found to reduce symptoms or indicators of oxidative stress caused by exercise. Trained athletes showed less evidence of lipid peroxidation to a given exercise and an enhanced defense system compared with untrained subjects. She reported that it is unclear whether the body produces sufficient antioxidants to counter oxidative processes or whether additional antioxidants are required, but she warned us that long-term high doses of antioxidants might have harmful side effects. Bottom line: consume a diet rich in antioxidants, and don't waste your money on supplementation!
Bengt Saltin and Bo Berglund delivered provocative addresses on altitude training, which were met with the usual discussion of "yes it works" vs "no it doesn't". Their presentations had begun by stating that the reduced maximal oxygen uptake at high altitude does not recover significantly during a prolonged stay and that training at high altitude improves performance only at high altitude. Bengt Saltin suggested that the same mechanisms involved in the decrease of max HR, red cell volume, and stroke volume are also at work during moderate altitude (1500-3000 m). In his words, "there is no effect of acclimatization on maximal oxygen uptake in athletes training at least at moderate altitude". The data also do not support a further increase in maximal oxygen uptake on return to sea level. Equally clear are the data on skeletal muscle adaptation: any positive effect of training at medium altitude would be primarily related to an elevated anaerobic energy release (possibly due to an enhanced buffer capacity and changes in the ratio of lactate dehydrogenase1-2 to lactate dehydrogenase3-4). So where does that leave us with altitude training? Well, "living high and training low" seems to work. The problem with that approach is the time involved in coming down to near sea-level in order to train. One possible way around the travel time is follow the Scandinavian approach and build "nitrogen houses" at sea-level that simulate altitude. We will have to wait and see if there are positive benefits to sea-level performance from such an approach.
Westerblad proposed that the early force decline during fatigue was ~10% in the central nervous system and ~90% in the muscle. The impairment in skeletal muscle involves a reduced ability to produce force, a reduced shortening speed, and slowed relaxation. The popular notion is that acidosis (due to lactic acid accumulation) is the major factor causing such impairment, but acidosis has little effect on contractile function at normal physiological temperatures. Instead, it would appear that the early force decline during fatigue is due to accumulation of inorganic phosphate and the additional force decline in severe fatigue seems to be caused by impaired intracellular Ca++ release due to localized energy imbalance (increased Mg++, reduced ATP, and/or increased ADP). He postulated that the reduced shortening speed seems to be caused by accumulation of ADP in the vicinity of the contractile proteins, possibly at the site of Ca++ release and uptake between the T-tubule and sarcoplasmic reticulum.
TESTS AND TRAINING PRESCRIPTION
A number of groups reported different ways of prescribing training intensity. Some German scientists indicated that they have used blood lactate testing for over 20 years and stated that lactate testing is still the most practical parameter for the evaluation of the individual training load. A group of scientists from Portugal reported that they used a similar testing protocol to that of the Germans, while they also use an analysis of ammonia kinetics. In addition, Rama reported that rating of perceived exertion and training impulse (based on Banister's definition of training load) were useful for quantifying training. Heart rate was not a good indicator of training intensity.
SWIMMING TECHNIQUE AND EFFICIENCY
Monique Berger and her associates in Amsterdam investigated the relationship between propelling efficiency and swimming velocity. Propelling efficiency depends on the amount of energy lost to the water by giving the water kinetic energy. The more energy given to the water, the less the propelling efficiency. Propelling efficiency increased with increasing velocity, but at the highest velocities some subjects showed a decrease in efficiency.
A Japanese team led by Futoshi Ogita investigated the effect of hand paddles on anaerobic energy release during supramaximal swimming. Their findings indicated that the faster swimming with hand paddles was due to mechanical factors such as higher propelling efficiency due to the larger propelling surface area and not due to metabolic factors.
How do stroke mechanics impact on swimming economy in freestyle swimming? Alves and Gomes-Periera from Portugal reported that a high elbow recovery and a long glide relative to the total stroke duration are associated with economy.
PROPULSION AND DRAG IN SWIMMING
Hideki Takagi and his Japanese colleagues presented a method for estimating active drag. The provocative finding: active drag might not be proportional to the square of swimming velocity as has been commonly assumed. Their data indicated that the exponent is less than two.
Peter Hollander and Monique Berger resurrected the old argument of whether drag or lift forces from the hands contributes more to propulsion. Neither drag nor lift can fully explain the propulsion produced by the hands in swimming, because energy losses due to force generation exceed those indicated by measures of oxygen uptake during swimming. The authors speculated that energy is recaptured from the water, possibly due to energy being absorbed from the vortices created by the hand and arm movements.
Does the shape of the hand affect force generation? Ross Sanders reported that he altered the shape of a hand model to yield four different shape conditions. The findings: thumb adduction did not alter drag forces, but affected the generation of lift. Palmar flexion of the wrist influenced drag as well as lift. The drag force was higher when the hand was flexed.
Ross Sanders presented implications arising from a study of lift and drag forces of the hand at all possible orientations. Continuous three-dimensional surfaces representing lift and drag coefficients as functions of pitch and sweepback angles were produced. The model included surfaces to take account of the effect of "added mass" occurring during periods of hand acceleration. The results showed clearly that the musculature surrounding the adducted thumb has a large influence on the magnitude of lift forces. The model showed that with intermediate pitch angles of around 45 degrees large forces are produced when the sweepback angle is near 45 degrees and 135 degrees. Swimmers may commonly attain 45 degrees of sweepback with 45 degrees of pitch during the insweeps of freestyle, breaststroke and butterfly. Swimmers may commonly attain 135 degrees of sweepback and 45 degrees of pitch during the outsweep/backsweeps of freestyle, breaststroke, and butterfly.
SWIMMING INJURIES AND REHABILITATION
The bane of many swimmers is shoulder impingement syndrome: the pain and disablement resulting from repetitive collisions of the rotator cuff muscles with the coraco-acromial arch. Bak presented a case for preventing and rehabilitating the problem by prevention programs focusing on supervised strength training in pre-adolescents to ensure proper function of the scapular stabilizers and shoulder rotators. Coaches need to focus on sound technique rather than high mileage to help swimmers avoid this injury.
Johannes Holz and associates from Germany emphasized the need for appropriate exercises to ensure appropriate muscle balance to avoid overuse syndromes in the shoulders. They found that age-group swimmers have muscular imbalances between the internal and external rotators. A strength training program was effective in correcting the imbalance.
Leif Sward highlighted the risk of lower back problems among adolescents. Scheuermann's disease, which includes disc degeneration, reduced disc height. He reported that Schmorl's nodes, an abnormal configuration of the vertebral bodies, were more common in athletes than non-athletes.
A group from the host country, Sweden, reported on the possibility of shoulder impingement being due to the thickening of the supraspinatus tendon. By comparing supraspinatus tendon thickness of the dominant and non-dominant arms of swimmers, tennis players, and soccer players, the group showed that overhead exercise increases the supraspinatus tendon thickness. Implication: overhead activity practiced from a young age may be a risk factor in the later development of shoulder impingement syndrome.
Training in water has become a popular way for injured players of many different sports to rehabilitate and maintain their aerobic fitness. Leen T'Jonck and her Belgian colleagues investigated the effects of water running in the rehabilitation of medial tibial stress syndrome (shin splints). The water training group significantly improved their VO2max by 7.5%, while the non-training control group decreased their VO2max by 3.9%.