DPT-403- Exercise Prescription: Aerobic Fitness

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As described in previous chapters, stamina fitness can be variously called aerobic fitness, aerobic power or VO2 max.  It can be thought of as the ability to take in, transport and utilise oxygen.  In physiological terms, this is measured as either a relative value -ml O2/ Kg / min – or an absolute value – L O/ min.  Designing aerobic training programmes is dependent on the short and long-term manipulation of the main principles of training – specificity, overload, intensity, frequency and duration (ACSM, 1998). 

A number of key training variables can be manipulated to stress the aerobic and anaerobic energy systems; therefore, presenting the personal trainer (PT) with a dilemma on what, when and how to implement the variables of training. It is noted, as with any form of programme design, there is no ‘golden rule’ or perfect way of prescribing exercise. Rather, there are a set of guidelines that must be adhered to, along with information on the client’s goals and a large chunk of imagination on the part of the trainer! What works for one client may be completely inappropriate for another – it is therefore, the purpose of this chapter to provide the trainer with the necessary information to enable them to prescribe effective aerobic training programmes for beginner, intermediate and advanced clients.

Benefits of Aerobic Training

It is stressed that prior to exercise programming, clients must be thoroughly screened to assess their current health and fitness status. At this point it is beneficial to review the benefits of aerobic training:

  • increase in stroke volume
  • decrease in resting heart rate
  • decrease in resting blood pressure (both systolic and diastolic)
  • increase in capillarisation
  • increase in the size and number of mitochondria
  • increase in number of red blood cells
  • increase in aerobic enzyme activity
  • decreased incidence of disease
  • mortality from all causes
  • coronary heart disease (CHD)
  • cancer
  • hypertension
  • non-insulin-dependant diabetes mellitus
  • osteoporosis
  • depression
  • improved ability to recover during and after training
  • decrease in percentage body fat
  • increased burning of fat at higher exercise intensities
  • ability to work aerobically at higher exercise intensities
  • enhanced sense of well-being

Adapted from ACSM 2001

These adaptations are beneficial for all individuals including unhealthy, beginner client right through to an elite endurance athlete. 

Types of Aerobic Training

Long slow duration (LSD) training:

LSD training is what is usually identified as aerobic training. It involves working for an extended period of time (usually 10+ minutes) at a fairly low intensity. The intensity of this type of training does not change throughout the session. Traditionally, LSD training has been used to develop an aerobic base for de-conditioned individuals as well as forming the majority of training for endurance-based sports such as the marathon. 

Interval training:

Interval training involves structured periods of work and recovery aimed at developing the aerobic and anaerobic energy systems. The benefits of this type of training are that as well as developing all of the physiological systems involved in LSD training, the body’s lactic acid tolerance abilities are also enhanced. When exercising at a higher intensity (which is the case in most sports and activities) enough energy can no longer be provided from the aerobic energy system. Therefore, the lactic acid energy system must be used to provide the remainder of the energy. Interval training improves performance in two key areas:

  • increased ability to tolerate high levels of lactic acid 
  • improved rate at which lactic acid is removed from the muscles

Fartlek training:

Fartlek is a Swedish term meaning ‘speed play’ and that is precisely what is done in this type of training – play around with the speed of training! It is an unstructured form of interval training where work is performed continuously for a certain duration, but instead of working at one intensity, as in LSD training, the intensity is varied in a fairly sporadic manner. This is an excellent way of performing interval training and can be a lot of fun; particularly if, for example, performed outside in a park. The session could consist mainly of jogging around the park but then some sprints could be thrown in, followed by some walks to recover.

Prescribing Exercise Intensity

Traditionally, aerobic exercise has been prescribed by working at intensities within a range of 60-90% of maximum heart rate. Whilst this is a fairly simple way of prescribing intensity it does present a number of problems:

  • 60-90% MHR is a very large range – is it better to work at the top end or the bottom end of this range?

Example:

A 20 year old client has been told by their trainer to work in the range of 60-90% MHR for aerobic training. 60% MHR for this individual is 120bpm, where as 90% MHR is 180bpm. This is a very large range indeed. If the client was fairly well conditioned, working at 60% MHR = 120bpm would create virtually no overload and therefore, very limited adaptations would occur. Conversely, if the client was fairly de-conditioned, working at 90% MHR = 180bpm would represent an intensity that would be too difficult to maintain for a period of time. This would be de-motivating for the client and would probably put the client off further sessions!

  • using % MHR to prescribe exercise intensity is very limited

Using the equation of 220 – age does give us a rough estimation of MHR; however, individuals of the same age can exhibit MHR’s that can differ by +/- 11 bpm above or below their age predicted MHR.

These factors both present the PT with the same problem – traditional methods of prescribing aerobic exercise are not specific to individual needs. There is, therefore, a need to find a way of effectively prescribing aerobic intensity that is both specific to individuals and to the activities that they participate in.

Metabolic thresholds:

During low intensity activities virtually all of the ATP that is regenerated is done so via the aerobic metabolic pathways. As exercise intensity begins to increase a point is reached where the aerobic energy system can no longer continue to provide all of the energy. At this point the body will have to start using the lactate anaerobic system to make up the shortfall. This point or threshold is the intensity at which the body will start to produce a small amount of lactic acid as the waste product of the anaerobic metabolism of glucose or glycogen. This is known as the aerobic threshold (AeT) and is defined as the exercise intensity where lactic acid levels first start to rise in the body.

The aerobic threshold (AeT) is identified by a sustained increase in blood lactate concentration above resting levels. This threshold marks the transition from aerobic metabolism to metabolism that is both aerobic and anaerobic. Exercise below the AeT threshold is comfortable, sustainable and ideal for recovery or long-duration work. Exercise beyond the lactate threshold is demanding but enhances performance by taxing aerobic respiratory mechanisms and improving one’s ability to dispose of lactic acid. 

As the intensity of exercise continues to increase beyond the aerobic threshold, the body starts to rely more and more on the anaerobic energy system and lactic acid production increases accordingly. This continues to a second point or threshold known as the anaerobic threshold (AnT). This point represents the highest sustainable aerobic intensity before lactic acid levels start to rise uncontrollably. The aerobic threshold and anaerobic threshold can be illustrated graphically as follows.

Using objective (heart rate and VO2 max) and subjective (RPE and breathing rate) data collected during the incremental fitness tests, it should now be easy to establish the AeT and AnT respectively. It is worth noting at this point that the lactic acid transition thresholds will be very specific to the exercise modality with which the test was conducted. For example, if the trainer measured the AeT and AnT on the rower, this would not carry over perfectly when prescribing intensity for running. 

Identifying Training Zones

As these thresholds will occur at different intensities and different heart rates for each individual, the trainer now has all of the necessary information needed to start prescribing a personal aerobic training programme. Based on the above information and for simplicity four specific zones are proposed. Using the table below it should be easy to prescribe specific zones of intensity for the client.

Zone 1 – recovery:

Recovery zone training comprises all intensities below the AeT. This type of training will produce limited adaptations to the aerobic systems due to the low intensity and associated lack of overload; however, this type of training is useful for the following purposes.

  • appropriate intensity for severely de-conditioned clients or those in special population groups
  • appropriate intensity for warm-ups and cool-downs
  • training in this zone can be used during ‘recovery’ sessions – typically performed the day after a very heavy session (both aerobic and resistance). This will promote recovery by increasing the blood flow to the working muscles. Recovery sessions would seldom be more than 30 minutes in duration
  • can be performed during certain phases of training when aerobic fitness is not a high priority – for example hypertrophy phases
  • most commonly used as the recovery intensity during interval training sessions. The exact intensity of recovery will depend on the intensity and duration of the work period of interval session

Zone 2 – aerobic threshold (AeT):

AeT training is performed at intensities between the aerobic and anaerobic thresholds. These intensities are usually performed as long, slow duration (LSD) training sessions. AeT training is the minimum intensity that is recommended to improve aerobic fitness and reduce disease (ACSM 2000). The following adaptations can be expected:

  • increase in capillary density
  • increase in myoglobin
  • increase in the number and size of mitochondria
  • increased energy stores (ATP, glycogen and FFA’s)
  • increased ability to oxidise fat and spare glycogen

However, exclusive use of this type of training will probably not provide huge increases in aerobic sports performance. AeT training can be performed for any length of time between 10 minutes to several hours. The duration of training within this zone will depend on the client’s fitness levels and training goals. The specific intensity will depend on the duration of training – the longer the session the lower the intensity within the aerobic zone. 

Zone 3 – anaerobic threshold (AnT):

AnT training is a very specific type of training performed at exactly, or as close as possible, to the anaerobic threshold. This type of training will maximise the aerobic benefits previously discussed as well as develop the client’s lactic acid tolerance and improve their ability to remove the waste products of anaerobic metabolism from the muscles. Training at AnT is demanding and should only be undertaken by clients who have an advanced level of conditioning. Even these clients might have to work up to performing a whole session at AnT!

Typically, AnT sessions last between 20 – 40 minutes with the recommendation to use a heart rate monitor to aid control of intensity. Ideally HR should not deviate much more that 2-3 bpm either side of the AnT heart rate. In conjunction with heart rate, RPE should be encouraged with the perceived intensity rate of ‘hard or RPE 13-15.

The main training response of this type of session is to cause a shift to the right of the lactic acid curve detailed previously. As a result the AeT and AnT will now occur at higher exercise intensities, indicating increased aerobic performance. For this reason, AnT is the best performance predictor in endurance athletes.

Zone 4 – anaerobic: 

Any intensity above the AnT is termed the anaerobic zone. Exercise at these intensities can not be maintained for long periods due to rapid increase in lactic acid. For this reason, interval training is the preferred method and is widely used. Using intervals has a number of benefits, these include:

  • more work can be performed
  • time efficient
  • increase in anaerobic enzymes
  • increased ability to buffer lactic acid
  • increase in VO2 max
  • burn more calories

Anaerobic zone training will improve the body’s ability to transport the waste products of anaerobic metabolism away from the working muscles. This is vitally important for activities that are intermittent in nature. In addition, endurance athletes who need to work anaerobically at times during a race or training session will benefit too. 

The specific intensity during interval training is completely dependent on the training goal of the client. For example, a 10,000m runner would benefit from longer intervals and shorter recoveries. The intensity of the work period would be only slightly above the AnT. Conversely, take an intermittent sport such as tennis, the work period of the interval would be of a higher intensity but of a lower duration. This notion introduces the idea of analysing an activity for the energy systems used and prescribing exercise that is specific to the demands of that activity. The following table provides some guidelines for suggested work : rest ratios when performing interval training sessions. 

Training emphasis (energy system)Work : rest ratio
Aerobic1 : ½ – 1:1
Lactate1 : 2 – 1 : 4
Phosphate1 : 6

The information contained within this table is only a guide. Performing interval training with varying work : rest ratios is beneficial for all levels of client and client ability (beginner to elite) as it varies the training stimulus. 

Programme Design Considerations

Beginners:

Beginners should undertake moderate intensity activities that are associated with minimal muscle soreness, discomfort and injury. It is recommended that beginners train 3 to 4 times per week and that the duration of sessions begins at 15 to 20 minutes and increases to 30 minutes (ACSM, 2000). Adherence will be optimised if the training programme is not initiated too aggressively. Beware, however, that the improvement in aerobic fitness of beginners is rapid and may plateau in as little as three weeks unless the training stimulus is increased (Hickson et al, 1981). For these reasons, the fitness professional should set realistic goals early in the exercise programme. The following ACSM guidelines are a useful starting point when designing aerobic fitness programmes for beginners.

VariableRecommendation
Frequency3 to 5 days per week
  
Intensity55/65% to 90% of maximum heart rate (HRmax)
 40/50% to 85% of HRmax reserve (HRR)
  
Duration20 to 60 minutes
  At least 20 minutes for vigorous activities 
  At least 30 minutes for lower-intensity activities
  
ModeAny activity that uses large muscle groups in a rhythmic nature, such as walking, jogging, running, cycling, cross-country skiing, aerobic dance, group exercise, rope skipping, rowing, stair climbing, swimming, skating, and various endurance games and sports. 

Intermediate exercisers:

The goal of this stage of training is to gradually increase the exercise stimulus in order to significantly improve cardiorespiratory fitness (American College of Sports Medicine, 1998). Intermediate exercisers can be progressed more rapidly than the beginner. Exercise intensity increases towards 80-85% of HRR and duration increases every 2 to 3 weeks until participants are able to exercise continually at a moderate to vigorous intensity for 20 to 30 minutes. It should be stressed that deconditioned and / or older individuals may take longer to adapt to a training programme. 

Advanced exercisers:

After 5 or 6 months, clients may or may no longer be interested in increasing the training stimulus, and the goal of training may become the long-term maintenance of cardiorespiratory fitness (American College of Sports Medicine, 1998). If this is the case, aerobic fitness can be maintained by training 3 times per week for 20 minutes (Hickson et al, 1982). However, cardiorespiratory fitness will be lost if exercise intensity is decreased (Hickson et al, 1985). 

Aerobic programme design examples:

The following two examples demonstrate how the PT could put together a week of aerobic training for their clients.

These two examples, demonstrate how AeT and AnTs allow the trainer to prescribe individual aerobic programmes. Fundamentally, in each of the above examples it is the training principles that have been adapted– intensity, duration and frequency. For example, client number 2 is unable (deconditioned) to complete 4 aerobic sessions per week and would also find a threshold session too difficult at this stage. 

The two examples above do not include any resistance training that a client may or may not be performing.

Furthermore, it is also important to point out that the above examples should be considered as such. Could they have been put together in a different format for both clients? Yes, however as long as AeT and AnT data is combined with the sensible application of training principles any number workout combination can be performed.

Student Task  

Using the data from your own aerobic and anaerobic threshold tests, write yourself an interval training session that you can perform in the gym during the following practical implementation session. The session should last for approximately 45 minutes and should include a specific warm up, main interval session and cool down. Think about the work to rest ratio of your intervals – do they match the demands of your chosen activity? 

Planning Long-Term Aerobic Training Programmes

Phases of training:

Variety is a key component in designing training programmes. Long-term success depends on successful manipulation of training variables over a period of time. Periodisation is the term given to the manipulation of training variables over time and is typically divided into phases (Hawley and Burke, 1998).  Dividing training into phases has a number of benefits:

  • helps prevent burn-out
  • more enjoyable
  • focuses on goal
  • reach goals in shorter time period

Specific phases include:

  • foundation or base training
  • transition or  threshold phase
  • speed or power phase

Foundation or base training:

This phase is used to establish what is called an aerobic base and to enhance those adaptations associated with improving VOmax.    Foundation training is most often characterised by what is known as L.S.D. (Long Slow Distance) training and can be quantified by working at AeT (zone 2) and AnT (zone 3) or RPE 11-15 for at least 30 minutes.  Alternative activities, which could be performed alongside this, could include postural correction and conditioning, and muscular endurance-based resistance training. 

Transition or threshold training:

The next phase of training is sometimes called the threshold stage (Hawley and Burke, 1998) or ‘early quality work’ (Daniels, 2001).  This is undertaken in the belief that it will increase the athlete’s ability to accommodate the changes in blood chemistry associated with higher intensity work and which can ultimately lead to fatigue.  Typically this phase consists of interval training type work (zone 3 and 4) where the client would perform work repetitions of five to ten minutes duration at an intensity equivalent to 85%- 95% vVOmax or 85%-95% HR max (RPE 16-17).

Speed or power phase:

Speed and power training enables the client to ’learn’ how it feels to work harder than normal, and should have a biochemical and neuromuscular effect in terms of ’teaching’ the relevant muscles to cope with faster velocities. Intervals are typically used in this phase where the client performs work up to three minutes in duration at an intensity equivalent to 95-100% MHR RPE 19.

In addition, athletes will go through an additional phase which may be called the ’taper’ or final quality phase of training. This is concerned with work that is of high quality but which leaves the client in a relatively fresh state so that they can perform at their target event as well as they are able to.  In terms of athletic training, this is quite a controversial area with many different theories and ideas passed around.  Again, it is worth pointing out that clients are, by and large, not full-time athletes and have other demands on their time. As a consequence, the basic guideline that can be given here is keep the quality of the work high, the duration and frequency low and make sure they rest well and eat properly.   

Final note: It must be stressed that training intensity is gradually increased throughout each phase. No phase consists solely of one method or training zone (intensity); rather, training will consist of a combination of different zones and methods, which will change throughout the year. Furthermore, to prevent overtraining and optimum benefit, PT’s must ensure adequate rest and recover between workouts and training phases.

Student Task

Design a 12-week aerobic training programme for an intermediate male exerciser who wishes to compete and achieve a personal best time in a local 10km race. At present he feels his training is stagnating and has asked you for help; as he is due to compete in twelve weeks time. He currently runs for 60-minutes on Monday, Tuesday and Thursday, with a 90-minute session on a Saturday. He is available to train on all days of the week and is prepared to follow your advice to the letter to achieve the above. 

Using the major training variables demonstrate progression over 12-weeks.

WeekMonTuesWedThuFriSatSun
1       
2       
3       
4       
5       
6       
7       
8       
9       
10       
11       
12       

References

American College of Sports Medicine (1998) The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults. Med Sci Sports Exerc, 30, 975-991.

American College of Sports Medicine (2000) ACSM’s Guidelines for Exercise Tesing and Prescription, Lippincott Williams & Wilkins, Philadelphia.

Daniels, J. (2001) in Foran, B(ed). High Performance Sports Conditioning.  Human Kinetics, Champaign, Illinois, USA. 

Hawley, J. & Burke, L. (1999).  Peak Performance : Training and Nutritional Strategies for Sport.  Allen and Unwin, Australia.

Hickson, R. C., Kanakis, C., Jr., Davis, J. R., Moore, A. M. and Rich, S. (1982) Reduced training duration effects on aerobic power, endurance, and cardiac growth. J Appl Physiol, 53, 225-9.

Hickson, R. C., Foster, C., Pollock, M. L., Galassi, T. M. and Rich, S. (1985) Reduced training intensities and loss of aerobic power, endurance, and cardiac growth. J Appl Physiol, 58, 492-9.

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