Muscle Activation in strength training exercises with and without using the clip-on device Gripper

Size: px

Start display at page:

Download "Muscle Activation in strength training exercises with and without using the clip-on device Gripper"

Jesse Hawkins
5 years ago
Views:

Muscle Activation in strength training exercises with and without using the clip-on device Gripper Contract research for Actiweight AS by The Norwegian

1 Muscle Activation in strength training exercises with and without using the clip-on device Gripper Contract research for Actiweight AS by The Norwegian School of Sport Sciences 2016 Responsible: Tron Krosshaug, PhD, Associate proessor, Department of Sport Medicine, The Norwegian School of Sport Sciences

2 Table of Contents Background... 2 Methods... 2 Study design and test subjects... 2 Tested muscles functions... 3 Exercises and execution... 3 Session 1: 1RM test... 4 Session 2: EMG-measurements at 70% of 1RM... 5 Electrode placement... 5 Equipment and data processing... 6 Warmup and load... 7 Placement of the Gripper device... 8 Randomization... 8 Instructions... 9 Results Bench press Pulldown Biceps curl Discussion Strengths and limitations Conclusion

3 Background The Norwegian School of Sport Sciences has conducted a contract research project for the company Actiweight, with the aim to study if a prototype of the training device Gripper can provide increased muscle activation during various strength training exercises. The Norwegian School of Sport Sciences have independently conducted the research without interference by Actiweight AS. Methods Study design and test subjects The purpose of this project was to compare muscle activation in arm and shoulder muscles in various exercises with and without the use of the clip-on device Gripper. Gripper is a spring loaded device that ads gripping resistance. In this project, Gripper was attached to a barbell in the bench press exercise, to a dumbbell in biceps curls, and to a pulldown grip. Ten male students were recruited from the Norwegian School of Sport Sciences. We selected persons who displayed good exercise technique and a minimum of 4 year experience with strength training. This was done to ensure consistent execution of every repetition and hence to maximise our ability to detect true differences between the conditions. Table 1 Age, height, weight and training experience for the 10 test subjects Age (yr) Height (cm) Weight (kg) Training experience (yr) Mean 25,5 181,8 85,9 7,5 SD 2,1 7,4 8,3 3,4 Each test subject was tested twice. In session 1, we measured maximal strength in bench press, pulldown (neutral grip) and biceps curls. In session 2, the subjects lifted series of 6 repetitions at 70% of their one repetition maximum (1RM) in the same exercises, with and without the use of Gripper. We used electromyography (EMG) to quantify muscle activation patterns. We randomized whether the subjects started with or without the use of Gripper 2

Tested muscles functions Five muscle functions were measured (Figure 1-5).

«Squeeze muscles» of the hand Figur 5. Elbow extension Figur 4. Elbow flexion Figur 3.

neutral grip as well as biceps dumbbell curls.

The feet were placed on the floor The pulldown was performed with a slight lean back of the trunk.

4 Tested muscles functions Five muscle functions were measured (Figure 1-5). A closer description of the detailed anatomy is found in Figure 1. Wrist flexor muscles Figur 2. «Squeeze muscles» of the hand Figur 5. Elbow extension Figur 4. Elbow flexion Figur 3. Shoulder flexion Exercises and execution We tested barbell bench press, close-grip pulldown with neutral grip as well as biceps dumbbell curls. The bench press was executed with self-preferred grip width, steady and controlled movement pace and no bounce on the chest. The head, shoulders and buttocks were required to be in contact with the bench at all times. The feet were placed on the floor The pulldown was performed with a slight lean back of the trunk. The hand and/or metal grip was required to touch the chest. The biceps curls were done with dumbbells on a scott curl bench. We required at least 160 degree elbow extension in the lower position. Additionally, we allowed only minimal movement of the upper arm. 3

5 Session 1: 1RM test The aim of session 1 was to find the 1RM load for each subject, for each exercise. The subjects were asked for their estimated 1RM, and based on this we designed a custom warm-up protocol (Table 2) Table 2. Warm-up program, with relative loads, based on their estimated 1RM. Bench press % of estimated 1RM Barbell only 40% 60% 75% 85% 95% 100% estimated 1RM Pulldown % of estimated 1RM 40% 60% 75% 85% 95% 100% estimated 1RM Biceps curl % of estimated 1RM 50% 75% 90% 100% estimated 1RM >100% >100% >100% >100% >100% >100% Number of repetitions per series Rest periods between the series Table 3. 1RM test results 1RM Bench 1RM Pulldown 1RM Biceps press (kg) (kg) curl (kg) Test subject Test subject 2 147, Test subject Test subject Test subject Test subject ,5 18 Test subject Test subject Test subject Test subject MEAN 123,55 105,75 19,2 4

6 Session 2: EMG-measurements at 70% of 1RM Electrode placement Table 4. The tested muscles in each exercise Wrist flexors «Squeeze muscles» Anterior deltoideus Biceps Triceps Bench press Pulldown Biceps curl We used the procedures described below for placing the EMG electrodes. In addition, we conducted visual and functional tests (e.g. squeezing and wrist flexion) to ensure that the recorded muscle activation actually measured these actions. Anatomical differences between the test subjects required this procedures. Triceps long head electrode placement - Starting posture: Sitting with the shoulder at approximately 90 abduction with the arm 90 flexed and the palm of the hand pointing downwards. - Location: At 50% on the line between the posterior crista of the acromion and the olecranon at 2 finger widths medial to the line. Biceps long head electrode placement - Starting posture: Sitting on a chair with the elbow flexed at a right angle and the dorsal side of the forearm in a horizontal downwards position - Location: On the line between the medial acromion and the fossa cubit at 1/3 from the fossa cubit. Anterior deltoid electrode placement - Starting posture: Sitting with the arms hanging vertically and the palm pointing inwards - Location: One finger width distal and anterior to the acromion Forearm electrode placement - Starting posture: Sitting on a chair with the elbow flexed at a right angle and the dorsal side of the forearm in a horizontal downwards position - Location: On the line between the humeral medial epicondyle and distal radius. The first electrode was placed 37,5% of the distance from epicondylus medialis to the distal ulna. The second electrode was placed three finger widths proximal and two finger widths medial to the first 5

Figure 8. Electrode placement on the anterior deltoideus, biceps, forearm and triceps.

Signals from each system were transferred via Bluetooth to Android tablets (Samsung SM- T310). We used the software Lommelab» from Biomekanikk AS to collect and process the data.

order high pass Chebychew filter. We removed the 6th (last) repetition from each series due to the possibility that the EMG activation pattern might have been affected by e.g. preparing to rack the barbell.

7 Figure 8. Electrode placement on the anterior deltoideus, biceps, forearm and triceps. Equipment and data processing We used two EMG-systems (Biomekanikk AS, FCC ID QOQWT12, model NG-01), each with two channels. Signals from each system were transferred via Bluetooth to Android tablets (Samsung SM- T310). We used the software Lommelab» from Biomekanikk AS to collect and process the data. The sample rate was 1kHz and an amplification of 220. The signal was rectified through using RMSprocessing and treated with a low pass digital filter of the type Hammond 50 taps, and a 4. order high pass Chebychew filter. We removed the 6th (last) repetition from each series due to the possibility that the EMG activation pattern might have been affected by e.g. preparing to rack the barbell. We recorded the peak EMG activation from each muscle for the statistical analysis (Fig 6). However, for muscles of the forearm, no systematic peaks were seen (Fig. 7). Therefore, the signals from these muscles were exported to Microsoft Excel where we computed the average activation through the 5 repetitions. A similar procedure was done for the triceps in the pulldown exercise, as there were no systematic peaks. Figure 6. Example of a signal with distinct peaks (bench press). Triceps (red) and anterior deltoid (blue). 6

8 Figure 7. Example of a signal without distinct peaks (bench press). Squeeze muscles (red) and wrist flexors (blue). Warmup and load The result from the 1RM test in session 1 was the basis for the warmup for the work series. Table 5. Load (% of 1RM) and nuber of repetitions during the warmup series Warmup series Measurements with and without Gripper 40 % 60 % 70 % 70 % Bench press load (% of 1RM) Kun 40 % 60 % 70 % 70 % stang Pulldown load (% of 1RM) 40 % 60 % 70 % 70 % Biceps curl load (% of 1RM) 40 % 60 % 70 % 70 % # repetitions pr series Rest between series (min) Table 6. Average absolute test load at session 2 Bench press Pulldown Biceps curl Average load at 70% 1RM (kg) 86, ,4 7

Maximum Voluntary Contraction (MVC) test We normalized the EMG measurements using separate Maximum Voluntary Contraction (MVC) measurements in separate, static tests.

We instructed the test subjects to give maximal effort for at least 5 seconds and measured the peak EMG signal in this period MVC for the forearm was measured using in a standing position, elbows

The test subject was instructed to flex maximally while the test leader gave resistance (no movement was possible) For the biceps, MVC was measured in standing position, 90 degree ebow flexion and

9 Maximum Voluntary Contraction (MVC) test We normalized the EMG measurements using separate Maximum Voluntary Contraction (MVC) measurements in separate, static tests. We conducted the MVC measurements after the work series on 70% of 1RM. We instructed the test subjects to give maximal effort for at least 5 seconds and measured the peak EMG signal in this period MVC for the forearm was measured using in a standing position, elbows flexed 90 degrees. The test subjects squeezed the gripper device (attached to a barbell) with maximal force. For the wrist flexors, the test subjects rested their forearm on a bench. The test subject was instructed to flex maximally while the test leader gave resistance (no movement was possible) For the biceps, MVC was measured in standing position, 90 degree ebow flexion and supination. The test subject attempted to lift (curl) a barbell that was resting in a rack, adjusted to their elbow height. The barbell was loaded so that no movement was possible. For the triceps, the same setup was used, but with pronated grip. The test subjects now pressed the barbell downwards with maximal force (similar to the push-down exercise) For the anterior deltoid, the test subjects were seated on a bench with back support (close to vertical), while attempting to perform a shoulder press with a bar that was loaded so that no movement was possible. For two test subjects, one of their MVC measurements could not be used. Therefore, the number of test subjects will vary between n=9 and n=10 in the results Placement of the Gripper device Gripper was placed where the test subjects will normally place their hand. Gripper was placed with the movable part on the finger side. It was oriented with the hinge at the pinky finger side. A B C Figure 9 a,b,c. Gripper attached in the bench press, pulldown and biceps curl exercises. Randomization To ensure that no bias was introduced from starting or ending with or without the Gripper device, we randomized the test order. However, we also made sure that 5 persons started with the Gripper device whereas the other 5 subjects started without the Gripper device. 8

10 Table 7. Randomization. Starting with or without Gripper. Bench press Pulldown Biceps curl Test subject 1 with with with Test subject 2 without without without Test subject 3 with without with Test subject 4 without with without Test subject 5 with without with Test subject 6 with without with Test subject 7 without with without Test subject 8 with with without Test subject 9 without with without Test subject 10 without without with Instructions When not using Gripper, the test subjects were instructed to squeeze the bar as they would normally do. When using Gripper, the test subjects were instructed to squeeze maximally (with both hands). 9

11 Results Bench press Bench press 120,00 Muscle activation (% of MVC) 100,00 80,00 60,00 40,00 20,00 0,00 Anterior deltoideus Triceps Triceps Underarmsfleksorer Forearm flexors Klemmemuskler Squeeze muscles med With Gripper Without uten Gripper Gripper Figure 10. Relative muscle activation (mean ± SD) in bench press with and without Gripper. Table 8. Measured muscles, number of test persons and relative muscle activation with and without Gripper in bench press. Statistical significance level P < 0,05. Bench press n Relative muscle Relative muscle Absolute difference Relative p activation without Gripper (% of MVC) activation with Gripper (% of MVC) (percentage points) difference (%) Triceps 9 78,77 82,07 3,3 4,2 P=0,19 Anterior deltoid Wrist flexors Squeeze muscles 10 72,27 81,53 9,26 12,8 P<0, ,60 15,56-1,04-6,3 P=0, ,53 74,25 22,72 44,1 P<0,05 We observed a 12,8% larger activation of the anterior deltoid in the bench press using Gripper. There was also a 44,1% higher activation of the squeeze muscles using Gripper 10

12 Pulldown Pulldown Muscle activation (% of MVC) 180,00 160,00 140,00 120,00 100,00 80,00 60,00 40,00 20,00 0,00 Biceps Biceps Triceps Triceps Underarms Wrist flexors fleksorer Klemmemuskler Squeeze muscles med With Gripper Without uten Gripper Gripper Figure 11. Relative muscle activation (mean ± SD) in pulldown with and without Gripper. Table 9. Measured muscles, number of test persons and relative muscle activation with and without Gripper in pulldown. Statistical significance level P < 0,05. Pulldown n Relative muscle Relative muscle Absolute difference Relative p activation without Gripper (% of MVC) activation with Gripper (% of MVC) (percentage points) difference (%) Biceps ,65 110,01 2,36 2,2 P=0,52 Triceps 9 16,77 20,38 3,61 21,5 P<0,05 Wrist 9 20,98 24,69 3,71 2,9 P=0,07 flexors Squeeze muscles 10 76,44 109,52 33,08 43,9 P<0,001 We observed a 21,5% larger activation of the triceps in the pulldown using Gripper. There was also a 43,9% higher activation of the squeeze muscles using Gripper 11

13 Biceps curl Biceps curl 250,00 Muscle activation (% of MVC) 200,00 150,00 100,00 50,00 0,00 Biceps Biceps Underarmsfleksorer Forearm flexors Squeeze Klemmemuskler muscles med With Gripper Without uten Gripper Gripper Figure 12. Relative muscle activation (mean ± SD) in biceps curl with and without Gripper. Table 10. Measured muscles, number of test persons and relative muscle activation with and without Gripper in biceps curl. Statistical significance level P < 0,05. n Relative muscle activation without Gripper (% of MVC) Biceps curl Relative muscle activation with Gripper (% of MVC) Absolute difference (percentage points) Relative difference (%) Biceps ,67 162,23 15,56 10,6 P<0,05 Wrist flexors Squeeze muscles 9 26,89 23,85-3,04-11,3 P<0, ,78 68,60 30,82 81,6 P<0,001 p We observed a 10,6% larger activation of the triceps in the biceps curl using Gripper. There was also a 81,6% higher activation of the squeeze muscles using Gripper There was a 11,3% lower activation of the wrist flexors using Gripper 12

14 Discussion Gripper gave increased muscle activation in several important muscles for the tested exercises. As expected, we found substantially increased activation of the squeeze muscles. The anterior deltoid is an essential shoulder muscle in the bench press, as indicated from the high muscle activation magnitude (apx 80% of MVC). We measured a 12,8% increase using Gripper. In a biceps curl, the biceps muscle is obviously essential, as indicated from the high muscle activation magnitude (apx 150% of MVC). We measured an increase from 146,67% of MVC to 162,23% of MVC with the use of Gripper, accounting for a 10,6% increase. In the pulldown, we obtained an increase in the triceps long head from 17,77% of MVC to 20,38% of MVC by the use of Gripper. This is a relative increase of 21,5%, but it is worth noticing that the muscle activation is relatively low. The use of Gripper gave relative muscle activation increases of 44,1%, 43,9% and 81,6% in the squeeze muscles for the bench press, pulldown and biceps curl, respectively. The squeeze muscle activation is particularly high in the pulldown with the use of Gripper (110% of MVC). For the wrist flexors, we found a relative reduction of 11% in the biceps curl. It is worth noticing that the relative activation level was low (< 30% of MVC) Strengths and limitations The test subjects were relatively strong, and we only needed to adjust the exercise technique to a minor degree. We could not visually detect any difference in movement technique with and without Gripper, meaning that the detected differences likely was caused by the squeeze effect of gripper, and not changes in exercise technique. However, we have not attempted to measure kinematics in this study. Surface EMG at the forearm may have crosstalk errors due to the many muscles on a relatively small surface. We were therefore unable to measure muscle activation in individual muscles. For this reason, we conducted extensive function testing when attaching the electrodes, to ensure that the desired muscle fuctions were captured EMG activation in a muscle gives a good indication of relative activation, but we cannot measure the muscle force generation. It is uncertain to what degree an increase in EMG activation levels will influence muscle hypertrophy and strength over time. Conclusion The use of Gripper gave statistically significant increases in the muscle activation of several essential muscles for the three exercises, as well as substantial increases in squeeze muscles of the hand. 13

THE GREAT EIGHT. Australian Institute of Fitness 1 / 13

THE GREAT EIGHT. Australian Institute of Fitness 1 / 13 THE GREAT EIGHT Australian Institute of Fitness 1 / 13 ABOUT THE GREAT EIGHT Exercises that is! Eight GREAT exercises. By now you should have opened your Master Trainer elog Book (see Welcome section)