Journal-Muscular Function Lab

7/30/2019 Journal-Muscular Function Lab

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Muscular Function Lab(Muscular Strength and Endurance)

Laboratory OrganisationThe lab groups split into two groups of eight to ten students for this lab. One group willmeet at the regular lab room to start the other group in the fitness centre to use weightroom facilities. These tasks will each take about one hour, the groups will then switchlocations for the second hour of the lab.

As there are only eight to ten students, the gym will not be booked and you willhave to share the facility with the campus community.

Introduction

Endurance versus StrengthThe correlation between absolute strength and endurance has been reported to exceed0.90 (de Vries, 1980; Invergo et. al., 1991). So clearly we are not talking about twoindependent measures of muscular function when we distinguish between strength andendurance. However, the correlation is not 1.00 and we know that specialized trainingcan certainly focus on strength or endurance for any given individual. The very nature ofstrength tests makes them unsuitable for the non-athletic population, so the majority oftesting you will be involved with is likely to be endurance testing. However, we will lookat some less intense methods of estimating maximal strength from work with sub-maximal loads.

Dynamic versus Static (Isometric) Strength TestsStrength can be functionally defined as the maximal weight that a person can lift (i.e. onerepetition maximal or 1-RM). Notice that all the strength tests performed in Kin 142 arestatic tests (handgrip and Jackson Evaluation tests). This is due to the difficulty ofdetermining the 1-RM in a dynamic setting. Movement velocity has been shown to be afactor in obtaining a consistent evaluation. Obtaining the 1-RM can be time consumingand fatiguing due to the hit-and-miss attempts at achieving one, and only one repetition.Isometric tests avoid this problem. However, most muscles groups are trained usingdynamic isotonic or isokinetic equipment, and we know that strength can be joint-anglespecific. Also many muscle groups are not used in an isometric manner and hence theresults of an isometric test may not relate to function very well.

Another problem with the isometric tests you have performed already in Kin343 is that

they need specialized equipment (Jackson equipment and handgrip dynamometers).Hence the methodologies discussed below, which can be used on any weight trainingapparatus, is often more practical as well as being more logically valid.

Absolute Strength versus Relative StrengthThe issue of calculating absolute or relative values is relevant to muscular functiontesting as it is in the case of the VO2max, (absolute in L/min and relative in ml/kg/min). Ifyou were testing an athlete absolute strength values may make more sense, as for


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example a lineman has to tackle whatever size of individual he encounters. For thegeneral population their strength to weight ratio is probably more relevant a measure todetermine if they have a healthy muscular system capable of providing them adequatepostural support and other strength requirements. For the strength tests below I haveprovided strength classifications based on both absolute and relative values wheneverpossible. Make sure you are using the same units (lbs or kg when calculating your

ratios)

Gettman (1988) recommends the bench press and leg press for assessing strength ofthe upper and lower body, respectively. More detailed tests are available one thatincludes six test items: bench press, arm curl, lateral pull-down, leg press, leg extensionand leg curl.

Table on the next page is from Hockey, Physical Fitness: The Pathway to HealthfulLiving, 1989.

Note that it is U.S. data and hence in pounds not kilograms.

Bench Press Strength (lb) in Adult Men and Women

Age (yrs)


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Standard Values for Bench Press Strength in 1-RM / Body Weight Ratio

Age

20-29 30-39 40-49 50-59 60+

Rating Men

Excellent >1.26 >1.08 >0.97 >0.86 >0.78

Good 1.17-1.25 1.01-1.07 0.91-0.96 0.81-0.85 0.74-0.77Average 0.97-1.16 0.86-1.00 0.78-0.90 0.70-0.80 0.64-0.73

Fair 0.88-0.96 0.79-0.85 0.72-0.77 0.65-0.69 0.60-0.63

Poor 0.55

Good 0.72-0.77 0.62-0.65 0.57-0.60 0.51-0.53 0.51-0.54

Average 0.59-0.71 0.53-0.61 0.48-0.56 0.43-0.50 0.41-0.50

Fair 0.53-0.58 0.49-0.52 0.44-0.47 0.40-0.42 0.37-0.40

Poor 1.56

Good 2.00-2.07 1.80-1.87 1.70-1.75 1.60-1.65 1.50-1.55

Average 1.83-1.99 1.63-1.79 1.56-1.69 1.46-1.59 1.37-1.49

Fair 1.65-1.82 1.55-1.62 1.50-1.55 1.40-1.45 1.31-1.36

Poor 1.15

Good 1.54-1.62 1.35-1.41 1.26-1.31 1.13-1.25 1.08-1.14

Average 1.35-1.53 1.20-1.34 1.12-1.25 0.99-1.12 0.92-1.07

Fair 1.26-1.34 1.13-1.19 1.06-1.11 0.86-0.98 0.85-0.91

Poor


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attempt at too low a weight and has had too many attempts before momentary musclefailure occurs. In this case muscular strength may be underestimated.

Obviously strength and endurance are muscle group specific, so the most accurate testshould test several muscle groups. However this can be time-consuming. The testbattery explained later in this manual uses seven tests in an attempt to obtain a valid

overall classification of muscular endurance. Limitations of this method of muscularendurance testing will be discussed in lecture.

Dynamic Muscular Strength (direct or predicted)

Work with a partner and determine the bench press and leg press 1-RM for at leastone of you. This test should not be too fatiguing so both parents could perform thesetests. If you are used to weight training choose a weight that you honestly believe isclose to your 1-RM. This would be done by doing a light warm-up set (10 to 15 reps),then choosing a higher weight and doing 5 or 6 reps not your 5-Rep Max of course.

Possibly attempt one more set but once you feel you are ready you would attempt amaximum lift (what you think is your 1-RM). If successful add 5 pounds to the weightand rest 3-4 minutes and try again, if unsuccessful the lift that succeeded was your 1-RM, if successful repeat until unsuccessful.

A simpler method is to keep trying to lift the first max-attempt weight you chose asmany times as possible. It may turn out that this weight was in fact your 3-RM or 5-RMbut you can use a predictive equation to calculate your 1-RM. However if you reallychose badly and after the first or second lift you feel you are going to do 10 or morerepetitions stop as the prediction equation discussed below becomes less accurate thefurther you are from 1 or 2 repetitions.

If you are experienced and you have an experienced spotter (or two) then you canperform a free-weight bench press. Otherwise use a machine.


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Estimation of One Repetition Testing Protocol Via an Equation

Another technique introduced in Kin 143 (since 2004) is to estimate the 1-Rm from any

known maximal repetitions up to 10 using the following equation. The higher the number

of repetitions you can actually perform with the chosen weight, the larger the error in the

estimate of your 1-RM.

From: Brzycki, m. (1993). Strength testing predicting a one-rep max from a reps-to-fatigue.Journal of physical education, recreation and dance 64(1), 8890.

This relationship is based on the relatively linear relationship between repetition maximal

scores and the percentage of the 1-RM. In general, the predicted force of 1-rm is based

on a decrease of around 2.5 percent of the 1-RM for each increase in the number of

maximal repetitions. The equation above has a sliding scale with a 2.78% reduction for

the first increase to 2-RM and averages out to a 2.5% reduction at 10-RM. The table

below gives you an idea of how this function works.

Estimated load for a 10-RM 8-RM 6-RM 5-RM 4-RM 3-RM 2-RM

is _____ of a 1 RM 75% 80.5% 86% 89% 91.7% 94.4% 97.2%

In case you are confused, lets look at an example. If a 25-year-old male can bench-

press 70 kg six times, the estimate of his 1-rm using the equation above is:

1-RM = 70 / [1.0278 (6 x 0.0278)]

= 70 / [1.0278 0.1668]

= 70 / 0.861

= 81.3 kg

After the warm-up and completion of the two strength tests complete the test discussedbelow. Again at least one partner should perform this test battery as this is anendurance test it is more suitable to a student unused to strength training.

Muscular Endurance

Test Battery (Heyward 1991)

Heyward, V.H. Advanced Fitness Assessment & Exercise Prescription (second edition).Human Kinetics Books, Champaign, 1991, pages 106-108.

Component: Muscular Endurance

1-RM =weight lifted

1.0278 (repetitions 0.0278)


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Equipment: Free or universal weights that allow performance of the followingstrength training exercises: arm curl; bench press; lateral pull-down; triceps extension;knee extension and leg curl. Mats for sit-ups. Use spotters if using free weightsoverhead.

Procedure: Subjects should determine their starting weights for the exercises by

referring to the list below. These starting weights should be entered on the data sheet toaid memory in a test-retest situation. Heyward actually uses 33% body weight forfemale triceps extension but this doesnt make sense to me and I wonder if it is indeed atypo.

Exercise Proportion of body weight to be lifted

Men Women

Arm Curl 0.33 0.25

Bench Press 0.66 0.50

Lateral Pull-Down 0.66 0.50Triceps Extension 0.33 0.25

Knee Extension 0.50 0.50Leg Curl 0.33 0.33

Bent Knee sit-up N/A N/A

It is assumed that the student understands the correct procedures for these weight-training exercises (refer to Kin 143 handouts).

Scoring: Subjects attempt each of the above six exercises and bent-knee sit-ups (onsit-up board set on second rung, with hands folded across chest) until they reachmomentary muscular failure or 15 trials. If the sit-up board is not available performstandard sit-ups. The total number of successful attempts (repetitions) are added up

and used to classify the subject's endurance on the table below. Note the maximumnumber possible is 105 (7 x 15).

Total Repetitions Fitness Category

91-105 Excellent77-90 Very Good

63-76 Good

49-62 Fair

35-48 Poor


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Standard Load Tests

These tests use a standard load and are classified as endurance tests. However somesubjects may be only able to perform one or two repetitions and therefore this wouldmore reasonably be a strength test for them.

YMCA Bench Press Test (optional)The YMCA uses this standard load test for the bench press, where males press 80 lbsand females press 35 lbs, and a metronome controls the cadence. Invergo (1981) foundthat this test in males was highly correlated to the 1-RM bench press test, whereaspush-ups to failure were not.

I would ideally like on partner to perform this test. After the tests already performed yourscores may be affected by fatigue so if possible a subject who only did the strength testmay be ideal. All students in the group should get data from a participant and use thetables below to classify the performance score. If you did the endurance test battery andstill want to try this test you could try this test on another day!

Component: Muscular Endurance (strength for some subjects)


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Equipment: The original YMCA test used free weights but you can use machineweights if spotters are not available. Use spotters if using free weights overhead.

Procedure: Males press 80 lbs and females press 35 lbs. Metronome is set at 60

bpm. The subject starts in the down position, elbows flexed hands shoulder width apart.A repetition is counted when the elbows are fully extended and the bar is then loweredto touch the chest. Up and down movements should be in time to the 60-bpm rhythm,which results in 30 lifts per minute. The test is terminated when the client is unable tocome to full extension or falls behind the 60-bpm rhythm. Count the number ofsuccessful repetitions and use the tables above to compare to the YMCA norms.

Muscular Power

Power is the product of force and velocity and is hence not really measurable in normal

strength training equipment, as the velocity of the muscle varies throughout themovement. Leg power is estimated in the vertical jump as we can determine thevelocity of take-off from the height jumped (due to our understanding of gravity).However more sophisticated strength training on isokinetic equipment does allow us tomeasure muscular force at various velocities of shortening. While not necessarily adirect comparison of a subjects potential maximal power output (as velocity is fixed) weshould discuss the use of these machines in strength (power) testing.

Isokinetic Strength (Power) TestingIsokinetic tests do exist. However, the speed of contraction is very crucial and hence itis difficult to compare results unless the angular velocities of the limb movements wereidentical. Different machines may also allow different patterns of motion and hence even

comparison of same velocity exercises from different machines may be erroneous.

The Heyward text does present tests developed for use on the Omni-tron system ifanyone is interested. This system does actually allow variation in velocity so at thecorrect setting it does allow muscular power to be tested. Setting the resistance high onthese machines allows an appraiser to measure strength, and, by calculating the workdone over 20 repetitions on a lower setting, muscular endurance can be estimated.Another method for measuring endurance is to measure the drop-off in time to completethe first four repetitions versus time to complete the last four repetitions (basically afatigue index). Please refer to the Heyward text for more information.

As we have no isokinetic machines in Pipers gym we will not be able to perform such

muscular power testing. However, most companies that build isokinetic systems havedeveloped batteries of tests (most without particularly useful normative data), so youshould check the company literature if you are working with isokinetic machines. Usinga Cybex for knee extension exercises is so prevalent in the rehabilitation of knee injuriesthat quite a bit of data is available for this specific exercise at various velocities.


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Laboratory Tests of Muscular Strength & Endurance(CPAFLA)

Equipment Needed

Hand Grip Dynamometer Gym Mat

Gym Mat marked for partial curl up test- Masking tape, metric ruler, pen, string, wire or Velcro strip

Set square Metronome

Measuring tape

Chair Chalk

Procedure

The detailed procedure and analysis methodology for these tests is outlined in the

CPAFLA manual p 7-38 to 7-51. (* note you are not required to do the sit and reachflexibility test at this time*)

CPAFLA handgrip strength (isometric [static] strength)CPAFLA push-ups (dynamic muscular endurance)CPAFLA partial curl-ups (dynamic muscular endurance)CPAFLA vertical jump (dynamic muscular power)

Keep in mind that for some individuals the push-ups and sit-ups may be more a dynamicstrength test than an endurance test.

Analysis

Determine the health benefit rating for each of the five measures, using the age andgender specific tables on p 7-47 to 7-48.

Record the Health Benefit Rating in Lab Book One.

Calculate Leg power output for a vertical jump score that is related to leg power.

Substitute body mass and vertical jump results into the following formula:

Leg Power (W)= [60.7 x jump height(cm) + [45.3 x body mass (kg)] - 2055

To convert kg m/sec to watts multiply by 9.804

Use Table 7-17 on p 7-47 or 7-48 to determine the Leg power Health Benefit Zone.

Enter your results in the Log Book.

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Journal-Muscular Function Lab