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Isotonic (Dynamic) Strength Lab

During Isotonic or dynamic exercises, the speed of the movement is variable throughout the

movement, such as when lifting a barbell. Thus, the load being lifted changes speed, due to the

biomechanical, physiological, and anatomical factors for the lifter, but the absolute load itself

(mass of load) does not change.

A popular free-weight exercise that is described as an isotonic or dynamic strength test in this

chapter is the bench press and can be measured directly or indirectly. For this lab, we are going

to be focusing on the direct measurement.

Rationale

The one repetition maximum (1RM) is the maximum load or weight that a person can lift only

one time. It can be directly measure from the maximal effort or it can be indirectly estimated

from a submaximal effort.

Directly Measured 1RM (Based on Estimated weight)

A direct measure of strength is the maximal weight that a person can lift in a prescribed manner

only one time.

If the person is cannot life it (estimated weight) with correct form, then a lower weight is tried

after a rest interval; if the person properly lifts the weight twice, then the participant stops.

After a small rest interval, small additional weight is added, and the person tries again. The

process with continue to occur until only one repetition is possible.

Indirectly Estimated 1RM

1RM may be indirectly estimated by knowing the number of submaximal repetitions to fatigue

(RTF) for any give weight lifted.

One indirect 1RM method is based on a Linear relationship between %1RM and the number of

submaximal repetitions to fatigue. If 4 repetitions to fatigue are completed, this would be

considered the number of repetitions or 4RM (4 reps to fatigue), 5RM (5 reps to fatigue) etc..

So using 80% of 1RM a person would be able to complete 8 repetitions

Curvilinear relationship is very similar to the linear method except that the estimated 1% RM is

mathematically base on the exponent of the number of repetitions to fatigue. This method yields

1RM that are slightly higher than the linear method when a low number of repetitions are

completed (3-5) but slightly lower estimates of 1RM with higher repetitions.

Anatomical Rational

The primary muscles involved include those of the chest (pectoralis major), Shoulders (Anterior

Deltoid and coracobrachialis), and arms (Triceps brachii).

Physiological Rationale

The biochemical pathway for maximal muscle actions that is, strength is the phosphagenic

pathway. Even the longest of 1RM movements is completed in less than 10s; this includes the

time spent holding the weight prior to the movement, raising the weight, holding it in the lifted

position and lower the weight

Tests of Strength (1RM), Work and Power

Strength testing serves purposes related to bother performance and health.

Before embarking on strength training programs, it is meaningful to evaluate the participants in

order to prescribe their programs and monitor their progress.

Novice programs with different individuals that exercise regularly because their bodies would be

adapted to the stress and would require heavier loads.

Additionally, measurements of work and power can be calculated

Absolute Strength Vs Relative Strength

Absolute Strength is the maximum amount of force exerted, regardless of muscle or body size.

Greater amounts of absolute strength favor those with higher body weight and in general, larger

individuals. Greater absolute strength will improve relative strength capabilities. Absolute

strength can best be represented by a client’s one rep maximum lift.

Relative Strength

Relative strength is the amount of strength to body size, or how strong someone is compared to

their size. This reflects a person’s ability to control or move their body through space, a vital trait

in all athletics. All else being equal, smaller individuals have higher relative strength.

Assume two people have the same absolute strength defined by a 1RM bench press of kg.

Further assume one-person weight 75kg and the other weight 85kg. This translates into two

different relative strengths 75kg/75kg = 1.00kg.kg-1 and 75kg/85kg = 0.88kg.kg-1.

Also, relative strength will be significantly different between untrained and trained individuals.

Purpose

The purpose of this lab is to familiarize the students with common exercise terms and

measurement associated with work and power as well as learning how to properly administer

1RM strength test.

Safety Check List:

1. Be alert of surroundings (Weights/bars on the floor) 2. Perform proper warm up prior to lifting 3. Use the hooked-thumb grip, no thumb-less 4. Check adjustable collars for tightness 5. Use spotters Wisely 6. Protect the back (keep weight close to body, avoid twisting 7. Proper breathing: Exhale/concentric Inhale/Eccentric 8. Children <16 and novice older adults >60 should not complete 1RM

Procedure:

1. Estimate 1RM: 40%, 60%,80% 90% 100% 2. Perform a 5 – 10-minute dynamic warm-up with activities targeting the muscles being

used such as arm circles and push-ups to prepare for the bench press

3. Load the bar with the weight corresponding to the subjects warm up weight (40% - 60% of perceived Max), then move into appropriate spotting positon behind the bench.

4. Instruct the subject to lie on his or her back on the bench in a five-point contact with the floor or bench (head, shoulders and upper back, right foot, left foot, and buttocks). The

participants body should be in a position on the bench such that the racked bar is directly

above his or her eyes. All repetitions should begin this way.

5. Lift the bar off the rack using alternate grip upon the command of the participant. Guide the bar to a position over the participant’s chest, then release the bar to the participant.

6. Have the participant lower the bar in a controlled manner to touch his or her chest at approximately nipple height while maintaining the 5 points of contact and inhaling.

During this movement, keep our hands in the alternated position near the bar but not

touching.

7. The participant should push the bar upward until his or her elbows are fully extended while maintaining the five points of contact and exhaling. At the end of the prescribed

number of repetitions or if maximum is achieved-grasp the bar with an alternated grip

and place it back on the rack.

8. After the participant completes 5-10 reps with 40% to 60% load, quickly change the load to the pre-determined second-set load. The participant will have only 1-minute to rest

during this change.

9. After the 1-minute rest interval, conduct steps 4 – 7 and have the participants perform 3-5 repetitions with the loads that is 60% to 80% of perceived maximum.

10. After the completion of set 2, the participant rests for 3-minutes while the you change the resistance to a load that is 80% to 90% of perceived maximum

11. After the 3-minute rest, conduct steps 4-7 and have subjects perform 1-2 repetitions with 80% to 90% load.

12. While the participant rests for 3-minutes, increased the load, depending upon how well the participant performed the previous attempt. If the attempt appeared relatively easy

increase by 5 to 10 Kg (10-20lbs); if however, the attempt was more difficulty, increased

the load by 1 to 5kg (5-10lbs), depending on the weight available.

13. Repeat steps 11 and 12, continuing to have the participant perform only 1 repetition until 1RM is achieved

14. If an attempt is unsuccessful, reduce the load (by 1 to 10 Kg) but keep it above the last successful attempt and have the subject rest for 3 minutes.

15. After the 3-minute rest, have the subject perform another attempt with basic procedures outlined above.

16. If the attempt is successful, increase the load by a small amount (1 to 5kg) and repeat step 15. If the attempt is unsuccessful, the 1RM load is determined the heaviest load

successfully completed. Record the maximum weight lifted in the appropriate location.

17. Divide the maximal weight lifted by the participant’s body mass and record the results in the appropriate location. The value should be compared with the data in table 4.4

Write Up: Include the following sections: Abstract, Introduction, Methods, Results, and

Discussion/implications, References

Results: 2 Tables

Table 1.

Muscular strength test

Class mean (kg)

Class df (kg) Male mean (kg)

Female mean(kg)

1RM Bench press

86.8 36.7 104.4 47.1

Table 2.

Perceived maximum Load (%) Kg Completed

Warm up 10 – 15 repetitions with bar

14.3 20.5 Yes

Set 1 5 -10 repetitions at 40% -60% of

perceived maximum

43.0 61.4 Yes

Set 2 3 -5 repetitions at 60% - 80% of

perceived maximum

71.0 102.3 Yes

Set 3 1 repetition at 90% of perceived

maximum

87.3 125.0 Yes

Set 4 1RM attempt 93.7 134.1 Yes Set 5 1RM attempt 100 143.2 Yes

Discussion:

1. Why is muscular Strength important? 2. Performing the 1RM what are some limitations that may have cause erroneous

readings? 3. How can a person’s level of fitness/ athleticism affect 1RM results? 4. How do the male and female results differ when examining absolute weight lifted?

Relative weight lifted? 5. Based on Individual data, how do you compare with the class averages?