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Ausdauertraining II

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Training for Aerobic Improvements "training at maxVO2 may, or may not, be the best methodology"

In Australian Swimming's recently published coaching manual the application of various types of training are discussed within the context of an integrated training model for swimmer development. The way in which training methodology is described is based upon a straightforward supply & demand analogy of the energy systems as they apply to swimming. However, factors such as age, maturity (and associated differences by sex), genetic potential, training environment, and lifestyle all have a profound influence on the end result of a training program. That's why any two swimmers in the same program will most likely react differently (sometimes the differences are slight, sometimes profound) to the group training stimulus.

Aerobic Capacity

Aerobic capacity is one physiological measure that seems (and with good reason) to attract our attention. We define aerobic capacity as the amount of oxygen delivered to the working muscles per unit of time (i.e. litres of O2 per minute). However, it's obvious that factors such as growth (larger body, larger lung capacity) and maturity (larger muscle mass) have a strong influence on aerobic capacity. Simply, aerobic capacity can change as the result of physical factors without a proportional improvement in the amount of oxygen available per unit of muscle mass. Scientists generally qualify the measurement to reflect these differences; one's aerobic capacity is generally interpreted in terms of millilitres of oxygen per minute per kilogram of body weight (i.e. ml/kg/min). Further, 'body weight' may not be a specific enough to tell us what we want to know, because it's muscle mass in relation to oxygen consumption that's important to us (i.e. fat cells don't help us to move the arms and legs in swimming). Body mass is therefore expressed in terms of lean tissue. Even this delimiting measurement may not be good enough, because the propulsion/resistance characteristics of swimmers are determined by body shape and not mass alone. Therefore, body volume (as an important hydrodynamic variable, influencing swimming efficiency), in combination with muscle mass, may be more important factors in determining one's capacity (Zwiren, 1989; and Grana, et. al. 1989); particularly during childhood/adolescent growth periods. Studies of children participating in sports training programs have reported varying results regarding the relative contributions of growth and maturation and training to improvements in aerobic capacity (Mercier, et. al. 1987). After recognising the differences in experimental protocols, the bulk of scientific evidence indicates that children and adolescents who regularly train using aerobic activities will increase their maxVO2 significantly more than would be possible by growth and maturation factors alone.

Now assume that an age-group swimmer's maximum capacity to consume oxygen increases, what are the likely outcomes in terms of performance? First, let's look at the nature of energy supply in prepubertal swimmers. There are two considerations: (1) what are the effects of energy supply at submaximal swimming velocities, and (2) what are the effects during high velocity (i.e. high intensity) swimming. At any given submaximal swimming velocity if the percentage of aerobic energy demand (i.e. in relation to the maximum available) is reduced, the metabolic efficiency will increase. In other words, if the swimmer places less physiological demand upon the body to sustain a submaximal swimming speed, overall swimming efficiency is improved. If other factors such as glycogen availability, swimming mechanics, etc. remain favourable, the net result is the swimmer's increased ability to sustain the workload. This is generally called 'fitness'. It's also the case that a swimmer's ability to perform greater volumes of work, at both low and high workloads, will improve (Yaacov, et. al. 1991). There are good reasons why swimmers should not concentrate exclusively upon training a single energy supply mechanism (Pyne, 1995) and Richards. During high intensity race swims, or repeat swims as used in a training set, it has been demonstrated that both anaerobic and aerobic energy contributions are important to children. Although prepubertal swimmers use proportionally more aerobic energy (this is due to a number of biological factors) to meet their race/training demands.

Aerobic Power or Aerobic Capacity - What's the Difference?

Increasing one's aerobic capacity can easily be seen as an advantage in swimming because of the increased potential for energy supply. However, statistical analysis of the characteristics of elite swimmers shows only a 'moderate' association between having the highest maxVO2 and being the most successful in endurance events (Troup and Daniels, 1986). The relationship varies because many physiological factors work together: (1) all three energy supply pathways must function simultaneously, (2) there are genetic and adaptive influences related to muscle fibre composition, and (3) lifestyle variations, psychological factors, etc. are different from one swimmer to the next. However, a strong association does exist between swimming economy at race speed and success in endurance events (i.e. races of 400m to 1500m). For this reason, sport scientists have concentrated their efforts over recent years on identifying specific points where energy supply is critical in relation to swimming velocity. How this relationship changes over the course of a training program helps to explain fitness adaptations. Each swimmer’s individual anaerobic threshold is associated with a swimming speed, oxygen consumption, blood lactate concentration, and heart-rate. If this point is reached at a very high percentage of one's maximum oxygen capacity, then a swimmer has better 'aerobic power'. Thus, aerobic power becomes a more practical measure, but aerobic capacity and aerobic power will together influence one's endurance potential.

Training to Improve Aerobic Capacity and Power

Three questions come to mind when planning a training program:

  • Are there critical periods of development when aerobic training can be used to best affect? This question actually has a number of implications. First, when considering a swimmer's career, it's suggested that the bulk of training activities for prepubertal swimmers should be aerobic in nature (Obert, et. al. 1996; Richards, 1996). Naturally, swimming skill and the development of speed must not be overlooked as part of the integrated training model. Second, when considering a seasonal training plan, improvements in aerobic capacity and aerobic power (together) provide the basis for specific race adaptations later in the season (Pyne, 1995). It’s important that sufficient aerobic work follows any period of detraining.
  • What volume of training should be devoted to aerobic work? Again, this will have implications based upon the age, maturity, and background of swimmers. There is also a consideration of how training volume triggers adaptation. Training prescription based purely upon volume will be inherently flawed because the effects of volume and intensity interact to stimulate adaptation. The volume-intensity relationship must also take into account the need for suitable recovery (the third factor in the adaptation equation). Therefore, very large volumes of daily work are possible at relatively low percentages (i.e. 50-60%) of one's aerobic capacity. Smaller volumes of work are possible at higher percentages (i.e. 85-95% of maxVO2) until the body has adapted to higher levels of stress, then greater volume of training may take place at these intensities. The volume of work that can be absorbed will depend upon the rate at which a swimmer is able to recover. Among young swimmers the volume of aerobic training usually remain relatively constant during a season; for older swimmers the volume may reduce (although it should never be eliminated) as training adaptations progress. Coaches are often frustrated when they're not provided with clear-cut prescriptions (i.e. 80% of training volume done aerobically at the start of a program and work down to 50% during specific race preparation, for example). However, you can see that the question, "how much volume is enough?" is too complex, and the variation between swimmers in any training group may be too diverse, to warrant a simple formula. What is simple, and practical, is regular assessment on the part of the coach. By using simple swimming performance tests the relative improvements or declines in aerobic measures (i.e. capacity or power, or both) can be determined and training volumes and intensities adjusted.
  • The third question is one of "what training intensity is best employed to improve aerobic potential"? Again, the consideration of individual variation within a population of swimmers poses a problem to a quick and easy answer. For example, consider that in addition to one's individual genotype there may be variations in one's sensitivity to training stimuli (Bouchard and Lortie, 1984). Some individuals show immediate response to either high or low levels of stimulation while others continue to absorb training volume (at either high or low levels of stimulation) and then respond all at once. The way to understand this phenomenon is to keep extensive records of each swimmer's training history and then adapt the program to reflect the way an individual best reacts to training stress. Here are some general guidelines the coach can use to help determine training intensity. First, swimmers who are 'less fit' (i.e. have a relatively low aerobic capacity because of limited training history, or recent detraining effects, etc.) require lower levels of stimulation to improve. Because the majority of coaches don't have the resources to measure aerobic capacity directly, they must rely on perceived exertion or heart-rate to estimate the percentage of aerobic capacity used. Light-to-moderate intensity (i.e. heart-rates of 40-50 beats/min below maximum) is usually sufficient to elicit a fitness response. Second, swimmers who have an accumulated training history (i.e. several years of training background) or a favourable genotype will adapt faster to training loads and will quickly require greater stimulation. Increased training volume at higher intensity (i.e. about 75% of maxVO2) will be required to improve aerobic fitness. Generally, this is 'moderately hard' endurance work performed at 30-40 beats/min below maximum heart-rate. Third, well conditioned swimmers will require aerobic loads of 75-85% of maxVO2 to elicit the required training response. This work is perceived as 'hard' and is performed at approximately 20-30 beats/min below maximum heart-rate. Once this level is reached, the coach must test regularly to determine if aerobic capacities are still improving or if they have plateaued. High levels of fitness can be maintained using reduced volumes of aerobic work, but this level of conditioning can not be maintained indefinitely. Eventually, even superbly conditioned swimmers will exhibit reductions of aerobic capacity if both volume and intensity requirements go unfulfilled.
    •

Even young swimmers will respond to these training principles. Evidence from research, as well as practical experience by coaches, supports this. A recently reported study involved prepubertal girl swimmers (average age 9.3 years at the start of the study), training over a twelve month period. They demonstrated a 38% increase in maxVO2, while a matched control group showed only a 13% increase on the basis of growth and maturity alone (Obert, et. al. 1996). It's interesting to note the training protocol for the study involved progressive loading of both training volume and intensity. The subjects began with three months of training with an emphasis on swimming skill. Training volume and intensity were initially relatively low. This was followed by eight months of training where volume progressively increased to 10-15 km/wk and finally peaked at 20 km/wk at the conclusion of the study (i.e. this training load is not considered to be excessive for this age group). Although the study was labeled as ‘intense swimming training’ an analysis of the methods indicated that workloads never exceed 90% of maxVO2 and progressively built-up from low levels to about 75-85% of maximum capacity during the later months of the study. The training load is similar many programs in Australia for 9-10 year-olds, and is consistent with guidelines suggested in ASI's Coaching Manual.

It's clear that young swimmers do not need high volumes of training at a very high percentage of their aerobic capacity to improve. This is not to be confused with using appropriate amounts of 'high velocity' training to improve anaerobic capacities (both lactic acid producing and alactic) of young swimmers. The overall limitations imposed by maturation factors will reduce the need for large volumes of work requiring a high anaerobic energy component. Yet many coaches still advocate training for junior swimmers that includes a substantial volume of high intensity training (i.e. well above 90% of maxVO2) for the purpose of developing aerobic capacity. In his book, Maglischo states, "What proponents of VO2max training failed to take into account was that athletes cannot maintain VO2max speeds for very long without becoming fatigued. Consequently, the volume of training that could be performed at these speeds is not sufficient to produce maximum adaptations in aerobic metabolism." In his book, Richards states that, "Prior to and during the childhood growth spurt it may not be advisable or necessary to program maximum aerobic training. . . . Sub-maximal aerobic training loads are more than sufficient to stimulate continued improvements among young swimmers."

In reality, the coaching literature is full of training prescriptions that use high-volume/high-intensity training sets. These may have a valid place within the program of senior age-group or elite senior swimmers if properly applied. The concerns of Maglischo that "training volume may not be sufficient" can be overcome to some extent if interval loads are applied using very short rest between swims. However, achieving and sustaining swimming intensity that stimulates maximum oxygen consumption is not easy. First, maximum oxygen consumption is not immediately reached, it usually takes 1-2 minutes to achieve, even when the effort is 'exhausting' almost from the start. Second, swimming velocity at maximum O2 consumption will only be sustained for about 3-5 minutes before neuromuscular fatigue and increasing lactate accumulation have a significant affect. Therefore, the swimmer must sequence the effort (for example 4 x 100m at a very high level of effort, with short rest, 5-10 sec., followed by a recovery swim and a repeat of the sequence). It's unrealistic to expect young swimmers to achieve sufficient volume of training, at this exhaustive intensity, on a frequent basis. Older swimmers will be able to absorb this type of training, provided suitable recovery training is also integrated into the overall training program.

Summary

Improvement in aerobic capacity is a desirable training goal for the development of swimming endurance and overall ability to absorb a variety of training stimuli. The concomitant goal of improving aerobic power may also be achieved through the prescription of training loads that represent as little as 60% (for unfit or novice swimmers) to 85-90% (fit swimmers) of maximum capacity. The resulting adaptations that occur produce a shift in the swimming velocity required at one's 'individual anaerobic threshold' (i.e. threshold speed becomes progressively faster). A greater percentage of aerobic capacity becomes available for sub-maximal performance, thereby improving energy efficiency through a range of swimming speeds. Programs that regularly require maximum aerobic capacity training loads do not seem to be warranted for prepubertal swimmers. Progressive loading of both training volume and submaximal intensities will produce the desired aerobic improvements. However, senior age-group and/or elite swimmers may effectively use training sets designed to elicit a maximum aerobic load. Whenever maximum aerobic training loads are used, there must be sufficient recovery (i.e. adjusting the intensity of other training stimuli to act as active recovery) between applications in the training cycle.

 

References

Bouchard, C. and Lortie, G. "Heredity and Endurance Performance". Sports Medicine, vol. 1, 1984.

Grana, W., et. al. (editors) "Swimming Economy: A Physiologic Perspective". In Advances in Sports Medicine and Fitness (Volume 2). Year Book Medical Publishers, Inc., Chicago, 1989.

Maglischo, E. Swimming Even Faster. Mayfield Publishing Company, Mountain View, California, 1993.

Mercier, J. et. al. "effect of Aerobic Training Quantity on the VO2max of Circumpubertal Swimmers". International Journal of Sports Medicine, vol. 8, 1987.

Obert, P. et. al. "Effect of long-term intense swimming training on the upper body peak oxygen uptake of prepubertal girls". European Journal of Applied Physiology, vol. 73, 1996.

Pyne, D. "The Specificity of Training - A Fresh Look at an Old Principle: Using Aerobic Training to Improve both Aerobic and Anaerobic Fitness". Australian Swim Coach (Journal of the Australian Swimming Coaches Association), vol. 11, no. 7, (Jan/Feb) 1995.

Richards, R. Coaching Swimming: An Introductory Manual. Australian Swimming Inc., Canberra, 1996.

Troup, J. and Daniels, J. "Swimming Economy: An Introductory Review" Journal of Swimming Research, vol. 2, no. 1, 1986.

Yaacov, A. et. al. "Oxygen uptake dynamics during high-intensity exercise in children and adults". Journal of Applied Physiology, vol. 70, no. 2, 1991.

Zwiren, L. "Anaerobic and Aerobic Capacities of Children". Pediatric Exercise Science, vol. 1, 1989.

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