Entries in Stress Test (2)


Heart Rate Variability (HRV), Recovery Index (RI) and Heart Rate Variability Index (HRVI)

By: Eddie Fletcher, Fletcher Sport Science Ltd 2007
A briefing note written by Sports Physiologist and Coach Eddie Fletcher
Accurate tools for assessing Psychological Stress, Physiological Workload and Recovery in Athletes

General Introduction

There are a number of factors which influence training and race performance, ranging from daily living (work and family), diet and hydration, cold, heat and humidity through to the lack of adequate rest and recovery. It is important to understand how stressful a normal training day is and to know the extent of overnight recovery.

The human heart is a wonderful barometer of the overall psychological stress and physical workload experienced by the body. The heart is a muscle, it gets tired and like any other muscle requires time to recover if optimum training and race performance is to be maintained.

The heart responds automatically and immediately to any increase or decrease in stress level. This heart rate response can be used to manage and mitigate the risk of over training, under recovery, illness or injury, to the body.

By monitoring the influence of psychological stress and physiological workload it is possible to use an analysis of heart rate to monitor overnight recovery and to moderate the duration and intensity of training to match the extent of recovery.

The consequences of getting it wrong should not be under estimated. Unless ‘listening to your heart’’ is normal practice deterioration in performance can occur almost unseen.

What are the benefits of measuring daily stress?

• Maximize recovery between training sessions
• Know how travelling, jetlag, high altitude and other stressors influence stress and recovery
• Learn how different daily routines enable and limit recovery
• Measure recovery between training sessions when training in high altitude
• Assess how travelling and jetlag influences recovery after a competition
• Check for social and psychological stressors that influence recovery
• Check athlete's daily routines for arrangements that could be done better to minimize stress during the day
• Interpret results together with athlete to detect stressors that influence recovery and to plan things that could be done differently in the future
• Repeat the daily stress recordings and observe how changes in daily routines influence stress and recovery

What are the benefits of measuring recovery?

• Detect early signs of overtraining or illness
• Optimize training load by finding the balance between training load and recovery
• Evidence based support for critical coaching decisions
• Record individual reference values e.g. during off-season when the body is recovered
• Check the recovery status during hard training periods
• Check recovery status when subjective feelings and fitness level indicates poor recovery
• Make sure that the body is recovered sufficiently before a new hard training period

How does it work?

Tracking daily stress and overnight recovery needs only one physiological signal – beat-by-beat heart rate data (the R-R interval). This measurement may be carried out during normal daily routines, whilst training and whilst sleeping. Although the data collection procedure is simple, the analysis methodology produces accurate recovery information.

Under resting conditions, healthy athletes show a periodic variation in the R-R interval. This rhythmic fluctuation is caused by breathing. Heart rate increases whilst breathing in and decreases when breathing out.

By accurately measuring the time interval between heartbeats (known as Heart Rate Variability HRV) it is possible to use the detected variation in time to measure the psychological and physiological stress and fatigue on the body. Generally speaking the more relaxed and free from fatigue the body is, the more variable the time between heartbeats. Increased Heart Rate Variability is linked to good health; decreased Heart Rate Variability is linked to stress or fatigue.

Heart Rate Variability also distributes as a function of Frequency.

Because of the characteristics of the increase (high frequency HF) and decrease (very low and low frequency LF) of the heart beat, changes in this frequency distribution can be used to monitor overall daily stress and overnight recovery.

Recovery is strongly associated with high frequency reactions and stress with low frequency reactions. These values are highly individual and the most sensitive markers for monitoring stress and recovery status. By looking at the difference from athlete specific baseline values the status of stress and recovery can be monitored and a

Recovery Index or Heart Rate Variability Index created.

The  intensity  of  stress/recovery  is  calculated  from  the  HF,  LF,  Respiration rate and HR.

How easy is it to collect the data?

Very easy, simply wear a Suunto t6 or Suunto Memory Belt during training sessions and overnight. The log is downloaded into Suunto Training manager software and Firstbeat SPORTS or Firstbeat PRO for detailed analysis.

What is a Recovery Index?

The Recovery Index is the relationship between the total duration of the Stress (low frequency) and Recovery (high frequency) reactions during an overnight measurement. The index is generally calculated from the first 4 hours of sleeping time as this time period is the most sensitive time for detecting recovery status. Average values provide information for both stress and recovery reactions during the selected time period indicating the relative strength of the reactions.

The intensity of the Stress/Recovery is calculated from the high and low Heart Rate Frequency mix, Respiration Rate and Heart Rate. The Recovery Index is represented by two numbers i.e. 60/100. The left number represents Stress reactions with the right number representing Recovery reactions.

Athletes need to measure their own individual baseline values at rest and compare subsequent values against the baseline figures.

What is a Heart Rate Variability Index?

Another useful tool for detecting recovery is the Heart Rate Variability Index

This is a single number and reflects the slowing down of the heart. The index can be used to detect recovery from an overnight recording. A high index figure represents increased recovery and a low value poor recovery.

During the day the value should be at least 15 but normally over 25. During the night the value should be at least 50 % higher (20-30) although athletes can have a value of several hundred (athlete above is 100 +). These limits are just guidelines; medication, heritage and training status also influence HRV level. Research indicates that these limits may be associated with burn-out.

As with the Recovery Index an individual baseline Heart Rate Variability Index value would need to be established for comparison purposes.


The ratio for this athlete is 42/100 and represents full recovery. For this athlete normal 100% recovery is 40-110

During a period of high stress for a different athlete a ratio of 117/74 represents under recovery. For this athlete normal 100% recovery range is 60-100

Tracking the Recovery Index

There are some endurance athletes whose heart rate level is so low during the night that despite the changes in HF and LF levels the night recording appears to show mainly recovery reactions.

The overall index may indicate 100% recovery when the underlying values show under recovery. It is important to get a reference level by measuring athlete specific baseline values in a rested state and comparing future results to the baseline figures.

In the example below note 100% recovery during the period 6/11/2007 to 18/11/2007.

Baseline resting values for this athlete 50 (stress)/115 (recovery)

By looking at the individual figures for stress and recovery the true extent of stress or recovery can be determined and compared against baseline level.

The intensity of the stress reactions

The intensity of the recovery reactions.

Normally when recovery increases, stress level decreases and vice versa. It will be noted that although the overall index shows 100% recovery for the 16/11/2007 the Recovery Index is approximately 85/100 which when compared against baseline 50/115.

Am I fully recovered?

More precise answers are obtainable with a long measurement history.

In this example the days when the athlete is recovered are marked on both the Stress and Recovery follow-up charts.

Stress reactions:

Recovery reactions:

Am I tired but training can continue? Am I tired and must rest.

These are the too hardest questions to answer and this is where the experience of the athlete and coach in using the Recovery Index is important. When the goal is to train hard and upset the body’s homeostasis the stress level should increase and recovery decrease.

In the charts above the hard training period was 18/10/07 – 25/10/07 (8 days). Based on the rate of recovery (recovery occurred within two days - see Recovery index 27.10.07) the overreaching period was successful.

The chart below is another athlete training at high altitude 12/10-07 – 27/10/07. The last measurement was 25/10/07. The recovery level was below baseline value all the time and the athlete reported subjective feelings of “big fatigue”. This 15 days hard training period without any easy days may have been too long. Time to reach baseline values after the training period took 10 days (recovery occurred 07/11/07).

When will I know I can train again?

After ending the last hard training period, the recovery level should be measured daily to see when the baseline values are reached again. In the example above, the new training period could be started on 07/11/07 or later.


Measuring recovery is a vital component of any training programme if an athlete is to maintain optimum training and race performance. ‘Listening to your heart’ must become normal practice to avoid deterioration in performance, illness or injury.

More information

Coaches and Athletes are referred to the following articles by Eddie Fletcher for more detailed information

Peak Performance Issues:

• 237 Heart rate variability – what is it and how can it be used to enhance athletic performance
• 246 Using HRV to optimize rest and recovery
• 253 Duration-intensity-recovery: a new training concept

Also see www.fletchersportscience.co.uk for further reference articles.

Eddie Fletcher can be contacted by email eddie@fletchersportscience.co.uk

Note: Some sections of this briefing guide are based upon copyrighted materials owned by Firstbeat Technologies Ltd. They are reproduced with the permission.


The Unexplained Under Performance Syndrome

By: Kathryn Bistany
From: Corpotential Limited: Fitpro Network.

Could an ‘off day’ actually be an indication of something more serious? This article takes a look at overtraining syndrome (OTS)

We’ve all heard of overtraining, also known as overtraining syndrome (OTS), staleness, chronic fatigue in athletes, sports fatigue syndrome and burnout.1,2

OTS should not be confused with over-reaching which reflects a temporary deterioration in athletic performance or short-term fatigue.3. With sufficient rest, the over-reached athlete should recover and show improvement.2 However if the intensity and duration of training are not reduced, this could lead to OTS. One of the main differences between over-reaching and OTS is in their recovery times. Recovery from over-reaching should take 2-3 weeks whilst OTS recovery could take several months.4.

The exact aetiology of OTS is not fully understood and there is no universal tool to predict its occurrence before it is clinically diagnosed.4 A number of hypotheses have been proposed in an attempt to explain the condition of overtraining syndrome (OTS), however the underlying mechanism(s) remains unclear. Many researchers agree that it is related to a dramatic increase of, or sustained periods of, high volume and/or intensity of training/competition with insufficient time for recovery.2 Yet, some would argue that looking at factors outside the specific training environment, such as relationships between the athlete and the coach, or personal relationships, are important as these could be a significant variable in OTS.1,5

Prevalence of OTS

The prevalence of OTS is difficult to estimate,5 hindered by unsystematic research with large variances in protocols from study to study.5, 6 This has resulted in the very existence of overtraining being questioned.7 A round table discussion was held in 1999 at St. Catherine’s College, Oxford, in an attempt to clarify the diagnostic criteria to be used in the future.1 It was decided to redefine the syndrome as unexplained underperformance syndrome (UPS), defined as ‘a persistent unexplained performance deficit (recognised and agreed by coach and athlete) despite two weeks of relative rest’. This was said to be a broad and all-inclusive definition which does not include over-reaching.

It is postulated that UPS is associated with suppressed immune function. This is associated with increased incidence and severity of upper respiratory tract infections (URTIs). There have also been reports of intestinal upsets, slow wound healing and increased sensitivity to environmental and food allergens. Alteration in immune cell function has also been recorded, which includes suppressed neutrophil function, suppressed lymphocyte count and proliferation, suppressed natural killer cell count and activity and decreased serum, nasal and salivary immunoglobulins.8, 2

Early Markers of UPS

Impaired mood state and subjective complaints are consistently described as sensitive and early markers of UPS and these usually start well before a definitive drop in performance.3 Other signs and symptoms include the following:

Physiological performance:
• decreased performance
• prolonged recovery
• decreased muscular strength
• loss of coordination
• chronic fatigue
• insomnia
• muscle soreness
• loss of appetite

• depression
• general apathy
• emotional instability
• difficulty in concentrating
• fear of competition

• increased susceptibility to illnesses
• allergies
• minor scratches heal slowly
• bacterial infection

• negative nitrogen balance
• depressed muscle glycogen concentration
• mineral depletion i.e. zinc, cobalt, aluminium, selenium, copper elevated cortisol
• low free testosterone

Athletes display different combinations of these symptoms with varying degrees of severity.9, 10, 4,2. Several factors contribute to UPS, including a sudden increase in training volume and/or intensity, heavy competition schedule, lack of periodisation, monotonous training programme, lack of programmed recovery and high self-reported stress levels regardless of whether they are directly related to training.5. Despite the fact that high cortisol has been recorded in some athletes with UPS, very little research is available on how to lower cortisol levels besides rest periods of several months.

Chronic secretions of cortisol need to be addressed as they can lead to the following:
1. A weakening of the immune system, making the athlete more prone to bacterial and viral infections.
2. A depletion of zinc and B6, which are needed to make hydrochloric acid (HCl) in the stomach.
3. An increase of fat in the abdominal area.
4. An increase in protein breakdown, leading to a loss of muscle tone.
5. An inability to heal wounds due to a depletion of zinc.
6. Increased sleep problems.
7. An inability to focus mentally as memory is impaired.
8. An increased possibility of insulin resistance which can lead to diabetes.

Although not all athletes with UPS will present with chronically high levels of cortisol, for those who do, a simple non-invasive saliva test can accurately reflect levels of cortisol. Clinical evidence shows a return to normal function in as little as six weeks or as long as nine months. Certainly more research is needed in this area but for the time being, for athletes showing signs of UPS and after excluding any form of disease or psychological problems, a simple saliva test may be worth considering.

Case Study

A 41-year-old female professional dressage rider and trainer presented with the following:
Lethargy, apathy, loss of appetite as well as an intolerance to numerous foods, tiredness all day and especially after light exercise, anxiety, an inability to concentrate or make decisions, poor memory, palpitations, mood swings and a need to be left alone.

This was affecting her riding and as a result, she was unable to perform the simplest task with her horse, from maintaining her posture to signalling to her horse for him to perform a particular exercise.
She slept whenever she could and kept away from people, feeling unable and unwilling to socialise.
Her blood test showed nothing out of the ordinary and a past history of her training regime did not show any change in training volume with ample recovery time. Her diet history showed that she normally had an excellent appetite and ate a varied diet.

However, in the last 18 months she moved to a new property which needed to be completely renovated and also sold several of her horses and moved to a new stable. All three incidences were highly stressful, each was laden with problems and it appeared she may not have been adapting to the stress.

An Adrenal Stress Index (ASI) test was recommended to ascertain her levels of cortisol (see below). The results showed low noon cortisol levels whilst her afternoon levels dropped below the reference range. This is known as pre-exhaustion or pre-adrenal fatigue. This pattern indicates long-term stress which depletes the adrenal glands caused by an excess cortisol response(11).

After a six-week period, following a protocol of supplements to support the adrenal glands and help balance blood sugar levels, the subject regained her energy, appetite, mental concentration and memory. Her dressage training improved above her own expectations as she was able to multi-task and keep her concentration.

The Adrenal Stress Test

The adrenal stress test is quick, simple and highly reliable. Four saliva samples are collected at four specific times of the day. The vials are sent directly to the laboratory for analysis and results are ready within 5-7 days.

It is important for athletes, coaches and trainers to realise that although adrenal stress is a growing problem, it is not irreversible. Recognising the problem in its early stages will speed up the recovery process, allowing the athlete to resume normal training.

Interestingly, body workers such as massage therapists, osteopaths and physiotherapists may be the first to notice one of the signs of adrenal stress: loss of muscle tone. Assuming there hasn’t been a change in training or any overt signs of any other medical condition or problem, it is hugely important for the nutritionist to get involved at this stage. Dealing with this problem correctly is the difference between the end of an athletic career or simply a learning lesson on the road to peak performance.

Kathryn Bistany

Kathryn Bistany is the Managing Director of Corpotential Limited which provides one-to-one nutritional consultations and group presentations. Kathryn is a qualified and practising sports nutritionist. For more information visit www.corpotential.com or contact 020 8994 3701.


1. Budgett R, Newsholme E, Lehmann M, Sharp C, Jones D, Peto T, Collins D, Nerurkar R, White P. Redefining the overtraining syndrome as the unexplained underperformance syndrome. British Journal of Sports Medicine 2000; 34(1): 67-8.

2. Lakier Smith L. (2003) Overtraining, excessive exercise, and altered immunity: is this a T-Helper-1 versus T-Helper-2 lymphocyte response? Sports Medicine, 33(5): 347-364.

3. Urhausen A & Kindermann W. (2002) Diagnosis of overtraining: what tools do we have? Sports Medicine; 32(2): 95-102.

4. Petibois C, Cazorla G, Poortmans J, Déléris G. (2002) Biochemical aspects of overtraining in endurance sports: a review. Sports Medicine; 32(13): 867-878.

5. Mackinnon L.T. (2000) Overtraining effects on immunity and performance in athletes. Immunology and Cell Biology; 78(5): 502-509.

6. Uusitalo A. (2001) Overtraining: making a difficult diagnosis and implementing targeted treatment. The Physician and Sports Medicine; 29(5): 35-50.

7. Halson SL, Jeukendrup AE. Does overtraining exist?: an analysis of overreaching and overtraining research. Sports Medicine 2004; 34(14): 967-81.

8. Dorshkind K & Horseman ND. Anterior pituitary hormones, stress, and immune system homeostasis. BioEssays 2001; 23(3): 288-94.

9. McKenzie D. (1999) Markers of excessive exercise. Canadian Journal of Applied Physiology; 24(1): 66-73.

10. Lakier Smith L. (2000) Cytokine hypothesis of overtraining: a physiological adaptation to excessive stress? Medicine and Science in Sports and Exercise; 32(2): 317-331.

11. Raber J. (1998) Detrimental effects of chronic hypothalamic-pituitary adrenal axis activation: from obesity to memory deficits. Molecular Biology; 18(1): 1-22.