505 Recovery rates and training (Pulse Oximeter)

Transcription

1 Sensors: Loggers: Pulse Oximeter None required Science in Sport Logging time: Not applicable Teacher s notes 505 Recovery rates and training (Pulse Oximeter) Read The Pulse Oximeter is a simple to use finger pulse detector. It was devised to record systemic peripheral blood oxygen saturation (SpO 2 ); the technology to collect that data also allows collection of pulse data. SpO 2 information is used by paramedics as part of the checks when first examining a trauma patient. In trained hands the values recorded can give indications of cardio pulmonary trauma. For us they are an interesting figure that is collected along with the pulse. The Pulse Oximeter works by pulsing infrared light into the finger mass, unlike tradition infrared pulse sensors which use a constant light source. The pulsing of the light makes the device more resilient to external light. Two types of infrared are used; one is in the visible range and one just beyond the visible. Comparing the results from both light sources further increases stability. It is assumed that students will have had experience of tracking the full recovery time before using this apparatus. While not essential it does help with the understanding of the measurements being taken. Apparatus 1. A Pulse Oximeter. There is no software or set up required for this method. The Pulse Oximeter has a display that indicates the pulse and SpO 2 values. All the student needs to do is read off the values according to the test regime they have developed. It is normally suggested that when using one of these devices you should adopt a pattern of taking the pulse at x minutes after the device starts producing a reading. Typically a value of 2 minutes is suggested. Notes The Pulse Oximeter gives the wearer a considerable degree of freedom of movement. It is advisable for each user to experiment and find out which finger gives the quickest response and which finger produces a pulse reading with arm movement. For younger students or students who have a slight frame you may find you need to use the thumb to get readings. The Pulse Oximeter gives the best readings if the light source is above the finger nail. There is a moulding mark on the case to indicate the optimal position for a finger. Additionally the moulded finger grip inside the sensor helps to locate the finger in the correct position. It can be a good idea to make a clear mark on the sensor showing the position of the light to help students quickly position the sensor. T505-1

2 Although the user can wear the sensor during exercise, it is better for the student to only wear the sensor at the time they will be taking readings. With organisation this should mean the several individuals can collect personal results from a single sensor. Refer to the instruction booklet that comes with the Pulse Oximeter, some have alternate display modes and sensitivities. There is a simple description of the meanings of SpO 2 values at the end of these guidance notes. Developing an exercise routine Any exercise used should not exceed the capacity of the individual to complete. Emphasise that the exercise is not a competition and is designed to give a fair test for comparative studies. Suggested maximum heart rates are found by; 210 (0.65 x age) For ages 12 to 18, Age Maximum heart rate Safe heart rate Over exertion should not be encouraged. Recovery times may vary from 5 minutes in fit individuals to over 15 minutes. An alternative is to decide a time frame and measure the heart rate at a number of minutes after stopping the exercise. Two minutes after cessation of exercise is an accepted time frame for this method. The rate from the time frame method is higher but does give a simpler and more accessible reference point for improvers and comparison. It should be expected that the heart rate of fit individuals will be lower, fitness increases stamina and stroke volume (that is the amount of blood pumped per beat). A larger stroke volume will give a lower heart rate. What this means 1. The heart rate depends upon activity. Even small changes in activity will change the heart rate. Anticipation of activity (or danger) will increase heart rate. 2. Heart rates will vary with age; younger people tend to have slightly faster rates than older people. 3. The time taken from the peak heart rate in exercise back to the normal resting heart rate is the recovery time. Recovery time is a good indicator of general cardiovascular health and condition. The most accurate tests take the subject to near cardiac collapse on a treadmill. Research has indicated that recovery times are a good prognostic indicator of death, i.e. very long times indicate poor cardiovascular condition and increased chance of an early death. T505-2

3 4. Slow heart rates are an indicator of fitness. Athletes (especially endurance athletes) have very low heart rates compared to their age cohort. Rates as low as 28 beats per minute have been recorded in Tour de France cyclists. 5. Quick or short recovery times indicate fitness. 6. You can monitor improvements in fitness using heart rates and recover times. You might not feel fitter, but your body responses to exercise will show that you are. The recovery time is very easy and simple measure of improvement. All you need is a watch that shows seconds and your finger tips to measure pulse; a Pulse Oximeter makes the task even easier. A chart will show improvement. Most people will show improvements within a few days, and you do not have to do big exercise, just stressing the heart rate by quick walking will do. Run up the stairs, don t walk! While the recovery time is a useful indicator of fitness it does not always help the athlete in training. They will need to know how much to exercise the heart and for how long. A common standard for calculating the desired heart rate in exercise is the Karvonen formula; this uses the resting heart rate and the maximum heart rate to calculate a training heart rate. The information is then used to create training zones which are designed to create conditions in the body to moderate respiratory activity. The information below is brief description of the Karvonen formula, a search of the web will quickly reveal schemes and modified version for specific training programs. Please note the information is for explanation. It is not a recommendation or an endorsement of a training scheme. As with all physical training, a full assessment of your fitness should be made before embarking on an improvement course. The Karvonen formula This is a heart rate reserve formula and it s one of the most effective methods used to calculate training heart rate. You need 3 pieces of information, 1. Your Resting Heart Rate (RHR) 2. Your age predicted Maximum Heart Rate (MHR) 3. Your training zone Calculating RHR You will need to determine your resting heart rate, this is important as the resting heart rate (RHR) is altered by the basic fitness of the individual. As you become fitter the RHR needs to be reassessed. If you are on long exercise regime you should reassess at least once every month. The RHR is normally measured first thing in the morning after awakening and before starting any activity of any kind, it should be calculated prior to getting out of bed in the morning. If you are going to measure your RHR you need to prepare. Getting out of bed and wandering across the room to collect a clock or Pulse Oximeter will substantially change the heart rate! To help assure accuracy, take your resting heart rate three mornings in a row and average the 3 rates together. If you are going to use an electronic monitor such as the Pulse Oximeter you need to have it at hand. Attach the sensor to the finger use the same finger each time you measure the RHR. T505-3

4 Position a clock so you can easily see the second hand or the digit change on digital clock. To take the RHR find the pulse on your wrist (radial pulse) or on the side of your neck (carotid pulse). Count the number of beats, starting with zero, for one minute. Calculating age predicted Maximum Heart Rate There are several formulae for calculating the MHR, The simplest = 220 age, Updated and allegedly more accurate formulae are, 217 (0.85 x age) (0.67 x age). 210 (0.65 x age) It probably does not matter which is used as long as you are consistent. The simple 220 age is considered to underestimate the MHR, but it is easier to remember and use. Typical training zones* 50% - 60% = low intensity for efficiency and recovery, 60% - 70% = optimal fat-burning zone, 70% - 80% = aerobic zone, 80% - 90% = anaerobic zone, or 90% - 100% = maximal zone. 1. Now take your age-predicted MHR and subtract your RHR. 2. Multiply the result of the subtraction by the percentage low-end and the percentage highend of the zone and the results you want to achieve. 3. Add back your resting heart rate to both the low-end and the high-end of the zone in which you want to train. The two numbers you are left with are the lower and upper heart rates in beats per minute for the training zone you have chosen. Worked example For example, Suzanne is 33 yrs old, has a RHR of 75 and she s just beginning her exercise program (her intensity level will be 50% - 60%). For simplicity the age predicted MHR will use 220 age. Suzannes's Minimum Training Heart Rate: (Age) = (Rest. HR) = x 0.50 (Min. Intensity) + 75 (RHR) = 131 Beats/Minute. (Note 0.50 used for 50%). Suzanne's Maximum Training Heart Rate: (Age) = (RHR) = x 0.60 (Max. Intensity) + 75 (Rest. HR) = 142 Beats/Minute Suzanne s training heart rate zone will be between beats per minute. After a few weeks of holding this level, she will want to introduce sessions (not every session) of the next zone up. T505-4

5 Periodically, take your pulse during your exercise session to gauge your intensity level. Typically (if not using a Pulse Oximeter) the easiest location for taking a pulse is on the side of your neck, the carotid pulse. Take care to not press too hard on the carotid artery or you ll get an inaccurate reading. Count the number of beats, always beginning with zero, for 6 seconds (then multiply by 10), or for 10 seconds (then multiply by 6) This will give the number of times your heart is beating per minute. If your pulse is within your training heart rate zone, you re right on track! If not, adjust your exercise workload until you get into your zone. Different sports will require different levels and mixes of training. The table below translates the zones to outcomes for cycling, distance running and simple keeping healthy regimes. Zone 1 Recovery Zone 2 Zone 3 Endurance Zone 4 Race pace Zone 5 Speed endurance Power Cycling Running Health / keep fit Establishes a good base level of fitness, for maintenance aerobic capacity lactate clearance by induced anaerobic respiration High intensity training, often on static trainers. Improves lactate clearance. Adaption to race/ sprint speed Establishes a good base level of fitness, for maintenance. Use after a hard work out on previous day Develops metabolic systems. aerobic capacity (stamina) lactate clearance. Encourage full use of carbohydrate to power muscle Improves blood flow and 0 2 carrying capacity. Improves endurance. Develops sprint finish Healthy heart zone Fat burning Aerobic Anaerobic Red line short intensity. No more than 2-3 times per week Zones are often regarded as a continuum rather than distinct separate stages. SpO 2 values The significance of SpO 2 falls outside the investigation, but curiosity will no doubt cause questions to be asked. At sea level expect to get values of 94 98%. At 5,000 feet above sea level expect to get values of 92 94% Blood saturation will vary with atmospheric pressure. The air pressure is the engine that forces the oxygen onto the red cells and controls how quickly it detaches from the cells. T505-5

6 Although the values are close, changes are significant. At sea level smokers and asthmatics will tend to cluster around the lower values while athletes / fit individuals will cluster at the higher levels. That is we would not expect a smoker to reach 97 or 98% values but there will be the odd person who will buck the trend. Values of less than 95% at sea level are considered to be of concern. Values of less than 90% are of sever concern. Values of less then 88% would require intervention with supplementary oxygen. What is good about the SpO 2 values is that they do show how well the body works to maintain the correct level of blood oxygenation. Even with intense activity the SpO 2 remains high there is a lot of adjustment of the body systems to create this stability. It does show the process of homeostasis over a complete system is being maintained, The constancy of the internal environment is the condition for a free and independent life"). (Claude Bernard ) T505-6