Perceived Exertion
Summary: There is no ________ _______ to assess perception of effort. Each method has ____________ and _____________. Careful and explicit _________ are required to obtain the best results.
"best" way advantages and disadvantages instructions
Ratio Scale Results
- Magnitude Estimation (arbitrary units) to Force in Newtons - when you measure perception of effort the most accurate way there is a curved linear relationship (1.6 not 1.0) -
The CNS correlates of perceived exertion
- We know much more about the neurobiology of pain than perceived exertion. Why? - can do studies on animals and guess if they are in pain but can't ask them their perceived exertion
0-10 Borg Scale
- curved linear - shows relationship between exercise stimuli and perception - has a true 0 and ability to go to infinity (Maximal - you can use a number beyond 10 - say if you felt the exertion was twice as hard as 10 you could say 20; gets rid of ceiling effect) - can compare one person to another more easily -1/2 number helps make ratio scale
Gunner Borg
- developed several valid methods for assessing perceived exertion - scientific emissary for perceived exertion since the 1950s - the most highly cited exercise psychologist
Absolute Exercise stimuli
- force - power output - treadmill and speed grade - weight lifted
Absolute Physiological responses
- heart rate - oxygen uptake - lactate
Study: Perceived exertion, lactate and heart rate in response to incremental cycle/treadmill tests in 2,560 men and women
- high correlation and high variability at each rating - biggest study ever seen - heart rate and perceived exertion is a linear response - correlation is .74 - a lot of variability - means that at perceived exertion of 16 some people have HR of 140 whole other have one at 200 - Lactate - quadratic association - at low levels of exercise intensity lactate doesn't change but perceived exertion is going up - if you look at anaerobic threshold relationship is linear- you can do a good job estimating perceived exertion from lactic acid build up after threshold
Effects of sodium bicarbonate ingestion (NaHCO3) vs placebo (CaCO3) on the relationship between hydrogen ion concentration and local ratings of perceived exertion in the arms and legs
- lower hydrogen ion concentration = lower RPE
Assessing Perceived Exertion
- most of the time measured with Borgs scale but sometimes for research measured with a ratio scale - This scaling system goes back to Stevens
Log: draw a figure predicting the weekly changes in local (leg) perceived exertion associated with the 12 weeks of leg curl training shown in the figure.
- perceived exertion would stay the same
Candidate brain areas involved in perceived exertion:
- sensory cortex - insular cortex - anterior cingulate cortex
Peripheral Physiological Mediators of Exertion
- summary done by Robert Robertson Relative Metabolic Intensity %VO2Max: <50% Respiratory: Limited Metabolic: Proportional Peripheral: Dominant Relative Metabolic Intensity %VO2Max: 50-70% Respiratory: Moderate Metabolic: Proportional Peripheral: Dominant Relative Metabolic Intensity %VO2Max: >70% Respiratory: Significant Metabolic: Proportional Peripheral: Dominant Peripheral = afferents sensing muscle force and byproducts (H+, bradykinin) Respiratory: respiratory muscle and lung afferents Metabolic = %VO2max - indirect - no receptor/afferents
Magnitude estimation
- you can have people rate stimuli with their own scale and people tend to discriminate similarly - even when power outputs are randomly presented out of order (100, 75, 90)
Perceived Exertion Scales
1. Borg's 6-20 - most commonly used - useful for most applications (PT, coach) - ordinal scale 2. Borg's 0-10 scale - ordinal but with ratio-like responses - for studying non-linear exercise responses (lactate)
Limitations of the 6-20 scale
1. Ceiling effect: people will give a lower number so they don't hit the ceiling too soon 2. Not a ratio scale: doesn't give you an accurate description 3. Assumes all maxes are perceived the same (range principle: range from lowest to highest for each person is the same)
Are RPE Ratings Valid?
1. Correlational evidence 2. Experimental evidence (stronger)
Limitations of HR method
1. Counting difficulties (baroreceptors in neck slow down heart rate) 2. Medication effects (beta blockers) 3. Emotion effects (anxious) 4. Position effects (swimming so your don't have to push blood against gravity)
Giving Instructions:
1. Define perceived exertion - how much effort are you putting into this? (feed-forward instructions - signal from motor cortex to muscles) - how much exertion do you feel? (feedback instruction - how muscles are feeling) 2. Explain differentiated ratings - overall - everything you feel - local - working muscles - central - chest 3. No right or wrong answer (just answer honestly) - won't be able to help them if they aren't honest 4. Anchor the perceptual range - present stimuli - by definition - Ex: give 30 watts and refer to that as 6 on Borgs scale and have them get to 330 watts and set that as 13 - Or do it by definition: through words tell them what low and high is (high is imagining you are 3 blocks away you your home is on fire; life death situation and low would be just walking at an easy pace)
Limitations of VO2 method
1. Expensive 2. Difficult to monitor directly
Experimental Evidence
1. Force, power output, treadmill speed 2. Psychological states: - few experiments (hypnosis) 3. Physiological states: - blood doping (taking red blood cells out for 3 months so they can generate more red blood cells, then give red blood cells back so they can deliver oxygen better and perform better) - fatigue responses induced by acute exercise duration (running same pace for 20 min is harder to do) {know experiment - instead of hold pace or speed constant (treadmill speed) , clamp the RPE at say 15 (hard) - What will happen to speed? Speed will decrease } - training induced adaptations - hypoxia - induced alkalosis
Limitations of RPE Method
1. Liars 2. Some lack perceptual abilities - kids under 10 - psychopathology 3. GXT estimation vs production - mode specificity helps - practice helps
3 Types of Ratio Scales
1. Magnitude estimation 2. Magnitude production 3. Cross-modality matching
Definition in words of the relationship between exercise stimuli and perception of effort:
As power output increases linearly, the perception of how intense the exercise stimulus feels grows exponentially.
Scale Type: Nominal
Classification - name - Ex: car has a licensed plate number to identify that car
Slide 31 REVIEW
Confused
Scale Type: Interval
Distances - tells you how much the distance is between the numbers - how far apart first and second place are
Magnitude production
Ex: asked to produce voice half as loud as the first noise - produce something that is some factor of what the stimulus was - can do this with weight as well
Exercise Prescription
Frequency, mode, duration & intensity Based on GXT: - oxygen consumption - heart rate - perceived exertion
Moderators:
Genetics: presume to have an effect but unknown (could have fast twitch fibers while someone else has slow twitch) Training: clear, large effect (RPE will go down with training) Exercise duration reliably influences perceived exertion Mode matters: both RPE-HR and RPE-lactate relationships depend on mode (swimming compared to running - HR response can change due to position)
Exercise intensity based on a duration up to 60 minutes
Intensity: 9 (very light ) HR% V02% reserve: <20 %MVC: <30 RPE: <10 Intensity: 11 (light) %HR%VO2 reserve: 20-39 %MVC: 30-49 RPE: 10-11 Intensity: 13 (moderate) %HR%VO2 reserve: 40-59 %MVC: 50-69 RPE: 12-13 Intensity: 15 (Hard) %HR%VO2 reserve: 60-84 %MVC: 70-84 RPE: 14-16 Intensity: 17 (Very Hard) %HR%VO2 reserve: 85 %MVC: 85 RPE: 17-19 Intensity: Maximal %HR%VO2 reserve: 100 %MVC: 100 RPE: 20 Red box: if you are training just average adults and try to increase their fitness then what is often recommended is training between 40-84 % or RPE 12-16 - you can prescribe exercise based on those ratings and still get them where you want them to be physiologically Purple box (6-100%): more for athlete training - trying to optimize your performance - coaches and athletes may do different intensities
Primary disadvantage of ratio scales
Inter-individual comparisons are not possible - if everyone is using a different system you cannot compare one person to another `
Psychobiological Gestalt
Many things are integrated to affect the level of perception of effort: - Exercise Stimulus: the bigger the stimulus the more you will perceive something as effortful (number of stairs; percentage of VO2max) - Physiological Factors: running a marathon next to someone who runs a 6 min mile will be different; you can change physiology with training - Psychological Factors: breaking up with someone may make perception of effort larger; or pacing yourself - Milieu (environment): running in january vs. june; practicing in practice vs game time
Summary
RPE is a valid measure of exercise intensity because: 1. It is moderately-to-strongly correlated to objective measures of exercise intensity, and most importantly, 2. Experimental manipulations in exercise intensity, physical capacity or relevant psychological states result in appropriate changes in RPE
Scale Type: Ordinal
Rank Order - someone comes in first, second, and third place (not very precise)
Scale Type: Ratio
Ratios - most scientific and best way to measure - has an absolute zero and goes to infinity - Ex: difference between interval and ratio - temp outside is 50 F which is not a ratio because when you get to 0 there is still thermal energy as opposed to kelvin scale when you get to 0 it is a true 0 and has absence of whatever you are measuring -
Study: Cycle ergometry to max during normoxia (normal O2) and hypoxia (reduced O2)
Slide 26 - having people mimic going to altitude by reducing the amount of oxygen delivered - two lines showing RPE ratings at relative and absolute intensity - Absolute: Vo2max drops down with hypoxia Relative Intensity: What you see is the lines are the same when data is expressed as a percentage of VO2 max - means that perceived exertion is strongly related to the relative exercise intensity (the percentage of someone's max) The key message is perception of effort is not strongly related to the absolute L of oxygen but mores strongly related to the relative exercise intensity - even when you manipulate it the RPE are still tightly related to the percentage of your VO2max
Steven's Power Law
Slide 9 - if you measure things in a ratio scale the magnitude of perception is going to be a function of the constant multiplied by the stimulus to the nth power - different modalities have different constants (exercise, sound, pressure, light) - BE ABLE TO USE FORMULA - Ex: given a constant k = 10, then given 100 watts (stimulus intensity) to the 1.6 power n= 1.6 for exercise
Borg's Range Principle:
The perceptual range is set equal for 2 people of different absolute abilities (review slide 16) - argues that it feels the same for everybody - yellow line represents someone with less capacity than blue line but both at maximal capacity feel the same
There is experimental evidence that ________ __________ and _________ ___________ play a role in perceived exertion.
central command afferent feedback
6-20 Scale related to heart rate response in what sport?
cycling - has a linear relationship - designed to estimate heart rate
Perceived exertion
how strenuous the exercise (exertion) feels or the perceived intensity of the effort given
Feed forward signal
information that comes from the motor cortex when you do a movement
Objective physical measures of the exercise stimuli and physiological variables that respond reliably to exercise stimuli are ______________________________ correlated with RPE
moderate-to-highly Correlations tend to be about .4-.6 (KNOW THIS NUMBER)
Cross-modality matching
the ability to match the intensities of sensations that come from different sensory modalities
Advantage of using a ratio scale:
yields most accurate description of the relationship between stimuli and perceptions
