Heart rate monitoring is easy to do, lots of people have a heart rate monitor but what information is it giving you? How do you use this for training, racing and recovery?
Here are the notes from this month’s talk.
HEART RATE MONITORING – WHY?
What is heart rate (HR)?
- 4 cardiac chambers contract in synchronised rhythm
- ECG trace (and RR interval = time between beats)
- Pulse – a peripheral representation of HR as blood passes along an artery
- Take HR at wrist, 2 fingers gently held against thumb side of wrist in line with index finger OR carotid artery in neck below front of ear/angle of jaw
- Heart rate monitors HRM– wrist or chest strap, detection of HR by colour of skin (wrist) or electrical impulse ( chest strap)
- Pulse/HR not necessarily the same in abnormal heart rhythms (eg atrial fibrillation AF or dropped beats)
- Sinus arrhythmia – HR speeds up on breathing in/slows down on breathing out – this is normal
What is a normal resting HR (RHR)?
Resting Heart Rate RHR = the number of times your heart beats per minute at rest
- manually before you get up or
- use a HRM with a RHR function which measures your RHR over the last 4 hours
Normal RHR varies from about 60 – 80, lower in fit people 40 – 50, < 40 for elite athletes
RHR will increase with
- Lack of sleep
RHR will decrease with
- Increased CV fitness
- Some medical conditions (hypothyroidism, Addisons disease, heart dysrythmias)
What is your maximal HR (HRmax)?
Standard formulae predict age related maximal values.
Most well known and easiest is:
HRmax = 220 – age (years)
eg 50 year old has a HRmax of 220-50=170
This formula works well for those under 50. But actual measurements show that older people over 50 in fact have a slightly higher HRmax than this formula predicts so for older people a more accurate formula is:
HRmax = 206.9 – (0.67 x age)
so now our 50 year old has a HRmax of 173, and a 70 year old has a HRmax of 160 (not 150).
For younger people, say 40, the HRmax predicted are equal at 180 and for those under 40 the second formula predicts a HRmax a couple of beats lower.
What controls HR?
Autonomic nervous system – think “automatic” ie not under voluntary control
- Sympathetic nervous system – fight or flight, hormones (adrenalin and cortisol)
- Parasympathetic nervous system – vagus nerve, neurotransmitters, digestion
What happens to HR during an exercise session?
- Increased sympathetic activity
- Exercise pressor reflex (increase in muscle activity and increases in intensity of exercise increase HR up to HRmax with maximum effort level)
- Cardiovascular drift – as exercise continues for a longer time, SV falls, and HR increases in order to maintain CO. VO2max falls and performance declines. So HR drifts upwards during a long session. Why? Skin cooling theory – as we get hot with exercise, skin takes more blood volume to cool us so blood returning to heart falls, SV falls. Not proven.
What is the long term effect of training on HR?
With training we get improvements in CV fitness:
- Increased stroke volume (SV
- Increased heart contractility
- Increased cardiac output (CO) during exercise
All of these contribute to reduced RHR ( as CO=SVxHR)
- HR monitoring for cardiovascular fitness
HR parameters which change as CV fitness improves include
- Lower RHR (Miguel Indurain, many times TdF winner had a RHR of 33. For most untrained people RHR is about 70).
- Lower HRmax. An athletes HRmax is around 10bpm lower than that of an untrained person, because their SV is higher.
- Faster fall in HR as you recover from exercise
|Max values (20 year old):||VO2 max l/min||HR bpm||SV mls/beat||CO l/min|
- HR monitoring for training
So now we know what HR is, how to measure it and how it changes as we exercise. But how do we use HR to tell us how to train? Training is carried out at different levels of intensity – some sessions are easy, some are moderately hard and some are very hard.
How can training intensity can be measured?
- lactate levels or % of VO2max – difficult to measure outside a lab
- rate of perceived exertion (RPE) – subjective, depends on how you are feeling that day. Scale is 6-20, aerobic threshold is around 14, LTHR (race pace) is around 16/17, 20 is maximal effort.
- HR zones – easy to measure/monitor/specific to the individual
Intensity of a training session can be measured by working at a % of HRmax. The different intensity levels are expressed in HR zones, each zone representing a range of HR for that individual. So to identify the HR zones for an individual, we need to either estimate them from formulae OR do a test.
- Estimated HR zones – for unfit individuals for whom a maximal effort test is inappropriate, or fit individuals without access to testing. HRmax can be estimated from their age and training zones calculated as a % of HRmax
- Sub maximal test eg Wattbike 3 minute test, estimates MMP and LTHR, does not take you to HRmax
- Race eg , TT race, 5km run race. A 5km TT race at maximal effort should be done at around 110% of LTHR, a 10km TT (15 minutes) at 107% and a 40km TT (1 hour) at 100% LTHR.
- Maximal effort test for HRmax, MMP and LTHR – only suitable for trained individuals Ramp test on Wattbike Using either of these 2 methods, training zones as a % of HRmax can be identified which are specific to the individual and tell you at what HR you should be exercising for an easy/aerobic/threshold/race at LTHR/above threshold level intensity.
See Carl’s Wattbike Training Zones from a Ramp test done here and his blood lactate curve from Bath University.
Points to note:
- “recovery” sessions are very, very easy
- At 60-70% HRmax you are in zone 2, still easy, should be able to have a conversation but will be getting an aerobic training effect, train for 30-45 minutes
- Training intensity needs to increase significantly to around 85% of HRmax to train aerobic threshold in zone 4
- Race pace is LTHR at 90% HRmax or zone 5. Sustainable for up to 1 hour in a max effort race. To train at lactate threshold you must train just above and just below this threshold. Intervals are short 2-5 minutes – it’s extremely hard.
- Zone 5 training at or above LTHR produces the greatest benefits especially for fit individuals
- Above zone 5 (zone 6 and supramaximal) trains sprinting only.
- As intensity levels increase, intervals get shorter
Take home message:
Make easy sessions easier and hard sessions harder and alternate between them.
Don’t train every day at the same moderate level somewhere in zones 2/3.
Only do 2 interval sessions in zone 5 weekly and not on consecutive days.
Don’t spend too much time in zone 4 – it’s tiring and you’ll get stale.
- HR monitoring for recovery
- Training is a progressively increasing stress to which we adapt and get fitter.( Stress increases sympathetic nervous activity and reduces parasympathetic, so HR increases)
- Improvements to our muscles and CV system occur during recovery. (Rest and sleep increases parasympathetic activity and reduces sympathetic activity, so HR falls)
- Without adequate recovery we cannot adapt and get more and more tired, leading to overtraining and poor performance
- Need to find a balance between stress and recovery
- Monitor recovery with HR changes in the mornings and heart rate variability (HRV)
Every morning when you wake, your body “whispers” to you what it can take that day – most of the time we don’t listen. Athletes keep a daily diary to monitor how they feel. Parameters measured include:
- Stress levels (exercise, work, finances, fear, diet, disease, alcohol, worry)
- Sleep quality
- Muscle soreness
- RHR every morning
The first four are scored on a scale of 1 to 7, with 1 being the best (eg 8 hours lovely sleep) and 7 the worst (no sleep at all). If any are 5 or more, that’s a warning.
RHR is scored as number of beats above or below their normal RHR (eg normal RHR of 45, one morning RHR 50, score is 5. If morning RHR is +/- 5 from normal, that’s a warning.
2 warnings – take training easy that day
3 warnings or more – don’t train that day
Also use HR with other parameters rather than alone to tell you how you are eg:
high HR/low RPE or low wattage = not well
low HR/ high RPE or high wattage = fit and well
low HR/high RPE and low wattage = not well
Heart Rate Variability (HRV)- some HRMs only
A measure of stress of any type, including exercise. HRV measures variation of the RR interval.
Take 2 athletes, one with RHR of 47, one with RHR 48. One is over trained, the other isn’t. How do we differentiate between the two? Use HRV.
Fit athlete training well with adequate rest and recovery has HIGH HRV
Over trained, tired athlete not resting enough has a LOW HRV
Some HRMs have a “sleep test” function, which measures HR and RHR over a 4 hour window starting 30 minutes after you go to bed. From HR/HRV a Recovery Index is calculated which tells you whether your recovery is adequate. If you train a lot and are in danger of overtraining, a HRM
with a “sleep test” function will help you to balance training volume/intensity with adequate rest and recovery.