Tuesday, 12 October 2010

Monitoring training load: quo vadis? #2

After having presented a simple method to monitor training load without the need of expensive equipment, it is now the time to discuss other methods which involve the use of equipment.

The first and obvious one is monitoring training with the use of heart rate monitors. Thanks to the development of technology it is nowadays possible to measure in real time heart rate (HR) of numerous players on the field without the need for them to wear a watch or a recording device. Many companies in fact provide telemetry systems capable of storing and transmitting heart rate values recorded during training and/or competition. When I first started working in this field may years ago I remember the excitement of being able to measure HR during training and be able to download the files for analysis using the conventional heart rate bands and watches. The cost was prohibitive (there was no way I could afford 20 watches + HR bands!), it took ages to download the files with 1 interface connected to a serial port, and most of all, because athletes needed to wear a watch…we had to be creative about where to place it and also be prepared to sacrifice a few in some contact sports or due to falls.

Nowadays, it is very easy! The current systems can transmit information in real time, it is possible to measure many athletes at the same time and it is possible to store and analyse all data immediately after the end of each training session. Furthermore, due to the improved quality of the sensors used and the software and hardware developments, it is also possible to measure R-R intervals and analyse heart rate variability (HRV).



Heart rate can be considered as a reliable indicator of the physiological load both for immediate training monitoring and for post-training analysis in almost every sport. However, considering the influence of psychological components like anxiety and stress on HR, it is feasible to suggest that an appropriate assessment of training intensity should also consider this limitation of HR monitoring.

Typical training plans of team sports are characterised by a combination of technical and tactical specific drills, small sided games, or general types of team drills. In the above situations, all members or small groups of the team perform similar tasks. The determination of training intensity and training stress is an extremely important parameter for training planning and for appropriate distribution of training load in elite athletes competing in team sports.

The following methods have been suggested to be effective in quantifying the training load:

The Training Impulse [TRIMP] method

Proposed by Bannister et al. (1975), characterised by the following equation:

TRIMP = training time (minutes) x average heart rate (bpm).

For example, 30 minutes at 145 bpm. TRIMP = 30 x 145 = 4350

This approach is very simple, however it does not distinguish between different levels of training. So it has been used mainly to determine general load in aerobic-endurance sessions.


Developed by Foster et al (2001)  is based on assigning a coefficient of intensity to five HR zones expressed as a % of HRmax:

1. 50-60% HRmax

2. 60-70% HRmax

3. 70-80% HRmax

4. 80-90% HRmax

5. 90-100% HRmax

The zone number is used to quantify training intensity; TRIMP is calculated as the cumulative total of time spent in each training zone.

For example

  • 30 minutes at 140 bpm. Max HR = 185 bpm. %max HR = 140/185 x 100 = 76%. Therefore, training intensity = 3.

TRIMP = training volume (time) x training intensity (HR zone) = 30 x 3 = 90.

  • 25 minutes at 180 bpm. Max HR = 185 bpm. %max HR = 97%.

Training intensity = 5. TRIMP = 25 x 5 = 125

The zone TRIMP calculation method can distinguish between training levels while remaining mathematically simple, however this can only quantify aerobic training and it does not allow quantification of strength, speed, anaerobic and technical sessions.


Combining the two methods allows the determination of training intensity not only from a cardiovascular standpoint, but also taking into account the perception of effort and can be extended to strength training to be able to collect a cumulative training load score.

EPOC (excess post-exercise oxygen consumption) Methods

EPOC is basically the excess oxygen consumed during recovery from exercise as compared to resting oxygen consumption. The EPOC prediction method has been developed to provide a physiology-based measure for training load assessment.

EPOC is predicted only on the basis of heart rate derived information. The variables used in the estimation are current intensity (%VO2max) and duration of exercise (time between two sampling points, Dt) and EPOC in the previous sampling point. The model is able to predict the amount of EPOC at any given moment. No post-exercise measurement is needed. The model can be mathematically described as follows:

EPOC (t) = f(EPOC(t-1), exercise_intensity(t), Dt) (Saalasti, 2003)

At low exercise intensity (<30-40%VO2max), EPOC does not accumulate significantly after the initial increase at the beginning of exercise. At higher exercise intensities (>50%VO2max), EPOC accumulates continuously. The slope of accumulation gets steeper with increasing intensity.

(The following figure is from Firstbeat Technologies Withepaper)image

The relationship between measured and HR derived EPOC has been shown to be significantly large suggesting this method as an alternative solution to determine training load with minimally invasive procedures such as wearing a chest band (Rusko et al., 2003).


And by the same authors has been shown to be related to blood lactate.


The EPOC approach has been nowadays introduced by various HR monitors manufacturers (www.suunto.com and www.firstbeattechnologies.com).

(Figure above from www.suunto.com)

Various manufacturers are now developing innovative approaches to describe training loads based on HR measurements (e.g. http://www.polar.fi/en/b2b_products/team_sports/software/polar_team2_software) and more will be available soon due to the ability for the current systems to record with high accuracy also R-R intervals and derive training stress information from Heart Rate Variability indices.

I will write more on these in the next posts on this interesting topic…this is it for now…stay tuned!


Iby Akubat said...

thank you for reviewing HR training load monitoring... in my experience it is generally an area very poorly understood especially in team sports where many coaches just want a measurement of "load" and are happy to see a number rather than ask how and where that comes from. As mentioned in your previous blog RPE is a very useful measure on intensity in the absence of HR. However according to Banisters work in the 70's & 80s intensity is only one term of an the equation for the calculation of "load" (time x intensity x weighting). It is the weighting factor that is probably the issue for most debate and many HR companies use time spent in zones generic and arbitary weightings which lack scientific underpinning in their calculation of load. In his later work Banister suggested that the weighting should be in accordance to an exponential formula he provided for males and females which was by all intents and purposes the blood lactate response to exercise. However he used the mean HR and this may not be indicative of the training of team sports players but also other athletes with current training regimens. As this was the focus of PhD i proposed that each individuals lactate response was used to formulate his own specific weighting formula, and to calculate the trimp for each HR reading provided to eliminate the disadvantage of mean HR in intermittent sports... recent published research has found very good relationships between this method of individualized TRIMP (itrimp) and changes in fitness and performance (Manzi et al, 2009)... my study currently in review suggested the same for soccer players...i also compared sRPE method and the banister method...these didnt show any relationships with changes in fitness...we can take a lot from the work of banister in the 70's and 80's... however in the intervening 10 years i feel ease of use an calculation has superseeded the need for accurate and valid quantification of internal training load, mainly driven by commercial interests of companies who provide HR systems. furthermore some of my research which i will present at a conference next year has also shown the usefulness of intergrating the iTRIMP method with distnace data from GPS units to predict fitness from normal training and match play. In my opinion without thorough individualisation the monitoring of load is pretty much pointless. As the data could be telling you a person is overtraining when they are not and for others vice versa... the training model presented impelizzeri et al (2005) shows that internal training load effects the training outcome...however apart his group of researchers very little other research out there has been conducted on refining the calculation of internal training load.

Dr. Marco Cardinale on 17 November 2011 at 05:54 said...

Thanks for your long comment Iby.
Very good comments, however not everyone is able to perform lactate testing due to costs, availability of tools and expertise/qualifications to draw blood. Every method has his limits. I know very well Dr. Manzi's work (we were colleagues 12 years ago in Italy) and I concur that that study had a nice approach with runners. We are all looking forward to read your published research.

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