The density of training can be defined as the frequency or distribution of training sessions or the frequency at which an athlete performs a series of repetitions of work per unit of time. The density of training can be thought of as a relationship that is expressed in units of time between working and recovery phases of training. Thus, the greater the density of training, the shorter the recovery time between working phases of training. When increasing the density of training, the athlete and coach must establish a balance between work and recovery to avoid inducing excessive levels of fatigue or exhaustion, which can lead to overtraining.
It is very difficult to calculate the optimal amount of time needed between multiple training sessions (e.g., within the training day or microcycle) because many factors can contribute to the athlete’s rate of recovery. The intensity and volume of training encountered within the training session plays a major role in determining the amount of time needed before another training session is undertaken. The greater the workload (i.e., intensity and volume) of the training session, the greater the amount of time needed to recover before preparedness or performance capacity is restored. Additionally, the training status of the athlete, chronological age of the athlete, nutritional interventions used by the athlete, and the use of recovery interventions can all affect her ability to recover from training bouts. Complete recovery from a training session is not needed before the next training session. A common strategy is to increase the density of training and promote recovery by using training sessions of differing workloads within the training day or microcycle.
Two methods are commonly used to optimize the work-to-rest interval during endurance or interval-based training: (a) fixed work-to-recovery ratios and (b) recovery durations that require heart rate to return to a predetermined percentage of maximum.
• Fixed Work-to-Recovery Ratios: Several researchers have used fixed work-to-rest ratios when studying interval-based training. By manipulating the work-to-rest interval, the coach and athlete can design a training plan that targets specific bioenergetic adaptations (see table at page bottom). Work-to-rest ratios of 1:1 or 2:1 target the development of endurance characteristics, whereas ratios of 1:12 or 1:20 target strength- and power-generating characteristics.
• Predetermined Heart Rate: Another method for determining the length of the recovery period is to establish a heart rate that must be achieved prior to performing another work bout. One method of using this technique is to set a heart rate range of 120 to 130 beats/min as the cutoff for the initiation of the next work bout. A second method is to set the recovery period as the time it takes the athlete’s heart rate to return to 65% of maximum.
Computing the density of a training session can be accomplished by calculating what is termed the relative density. The relative density is the percentage of work volume the athlete performs compared with the total volume within the training session. The relative density equation is as follows:
Relative density = Absolute volume x 100
Relative volume
The absolute volume is represented by the total volume of work that the individual performs, whereas the relative volume represents the total amount of time (duration) for a training session. Let say that the absolute volume of training is 102 min and the relative volume is 120 min; the relative density of the training session would be calculated as follows:
Relative density = 102 x 100 = 85%
120
This calculated percentage suggests that the athlete worked 85% of the time. Although the relative density has some value to the athlete and coach, the absolute density of training is more important. The absolute density can be defined as the ratio between the effective work an athlete performs and the absolute volume. The absolute density or effective work is calculated by subtracting the volume of rest intervals from the absolute volume using the following equation:
Absolute density = (Absolute volume – Volume of rest intervals) x 100
Absolute volume
Let’s say that the volume of rest intervals is 26 min and the absolute load is 102 min. The absolute density would then be calculated as follows:
Absolute density = (102 – 26) x 100 = 74.5%
102
These calculations indicate that the absolute density of training was 74.5%. Because training density is a factor of intensity, the index of absolute density could be considered medium intensity. Determining the relative and absolute density of training can be useful for establishing effective training sessions.
Work-to-Rest Intervals and Bioenergetic Specificity
Targeted energy system Average work time (s) Work-to-rest ratio
ATP-PC 5-10 1:12-1:20
Fast glycolysis 15-30 1:3-1:5
Fast and slow glycolysis 60-180 1:3-1:4
and oxidative metabolism
Oxidative metabolism >180 1:1-1:3