The effects of accommodating resistance training on the development of motor learning patterns





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The effects of accommodating resistance training on the development of motor leaning patterns
The development of motor control patterns to achieve functional transfer to increased sports performance is an objective of many strength and conditioning programs. Motor control refers to how the nervous system controls coordinated movements in terms of the relative importance given to movement commands specified by central components of the control system and the environment. Theory that gives command specified by the nervous system, that provide the basis for organizing, initiating and carrying out intended actions is known as a motor program (Magill, 2001).

Dynamic pattern theory is being investigated as an approach of motor control theory describing the control of movements that emphasize the role of the environment and the dynamic properties of the body and limbs (Magill , 2001).
Previous research has indicated that the cerebral cortex receives information from the proprioceptors that transform this information and send the appropriate pattern of signals to the motor cortex ( Siff, 1999). Proprioceptive feedback is associated with the performance of all physical tasks. The greater the proprioceptive sensitivity, the higher level of skill with all other aspects constant related to performance (Dickinson, 1974).

In this study, a changing environment has been created in the weight room by the deployment of large rubber bands to accommodate the resistance in a conventional exercise such as the barbell squat. The bands are used to change the strength curve by increasing the load as the participant ascends in the squat motion and decreasing the load on the descent ( Siff, 1999 ). The band also creates an unstable environment. Also the bands provided for a rapid decent which allowed for greater eccentric muscular contraction to activate a myotatic stretch reflex to increase reversal strength ( Granit, 1970 ).

The aim of the study was to establish a relationship between the development of motor patterns and transfer of learning to a performance based outcome. The hypothesis of the study is that the use of bands with weight training will develop motor learning patterns at an increased rate than the control group, that will transfer to other specified tasks. The itertask transfer developed is being measured is exploring a relationship between speed strength and absolute strength ( Schmidt, 1975). The motor patterns will create an increased rate of stabilizer muscle recruitment, a greater rate of force development and increased nervous system response to account for the changing load. The box squat was chosen to overload the muscles of the posterior chain being the hamstrings, spinal erectors and gluteals. These muscles are vital to the development of power( Poliquin, 1997 ).


METHOD

Participants

The participants (N=4) were four male powerlifters with a mean age of 30.5 years. All participants had at least one year of competitive experience and had attained “A Grade” competitive total or higher. All participants had competed at state and national championship level competitions.

Apparatus

A modified power rack with band attachments was used, as well as a standard Olympic Bar and numerous different sized weight plates. The rubber bands employed were four mm natural gum rubbers with widths of 45mm and 30mm. Reinforced wooden boxes from 5’ to 2’ were used as well as weight belts. Three stopwatches were used in conjunction with assisting video cameras and recording equipment also.

Procedure

Procedure involved participants performing a sequence of eight sets of two repetitions of box squats. Rest intervals between sets were timed to forty-five seconds. Box heights for each participant were set so that when the participant was sitting on the box, the top of their thigh would be one inch below parallel to the floor.
Participants received instructions as to perform the squat. The squats were performed by pushing the gluteal muscles towards the rear, so that once sitting on the box the shins are at a ninety degree angle to the floor to place minimal stress on the patella tendon and load the muscles of the posterior chain, being the spinal erectors, hamstrings and gluteal muscles.
Once the bar was unracked, participants were asked to push the abdominal muscles against the belt, to activate core stabilizer muscles and increase intra-abdominal pressure.
Participants all performed sets with sub maximal weights. Objectives for the participants were given as speed, acceleration and reversal off the box. Repetitions were performed under control allowing for a fast eccentric phase of the motion.
Group one performed weeks one and two with loads at sixty per cent of a competition rep maximum. Weeks three and four were performed at sixty-five per cent.
The load for group two was performed at fifty per cent of one repetition competition maximum. The additional tensions of rubber bands were used allowing for a calculated average of fifteen per cent at the top of the squat, deloading to seven per cent when on the box. Giving a contrast of sixty-five per cent at the top and fifty-seven per cent at the bottom for weeks one and two.
During weeks three and four, additional band tension was used with twenty-four per cent at the top and twelve per cent at the bottom. Bar weights were reduced to forty-six per cent of competition one repetition maximum. Giving percentages of seventy per cent at the top, deloading to fifty-eight per cent at the bottom.
Sets were timed manually with stopwatches used by three independent observers. Means were calculated for the three recorded times and recorded in the results.
The timing commenced at the initial movement of the participants hips as they began to move backwards and down, and ceased upon completion of the second repetition with the participant standing upright.



RESULTS
Tables 1-4 indicate results of speed and mean speed of sets performed over the four week trial. Tables 1 and 2 used accommodating resistance band and tables 3 and 4 were the control group.

Table1. Participant 1

Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 Set 7 Set 8 Mean
Trial 1 3.87 4.28 3.58 3.39 3.58 3.91 3.73 3.48 3.73
Trial 2 3.84 3.85 4.06 3.68 3.96 3.84 4.10 3.81 3.89
Trial 3 4.07 3.88 3.74 4.10 3.77 3.68 3.60 3.73 3.82
Trial 4 4.40 4.02 4.24 3.76 3.82 3.78 3.98 4.17 4.02

Table 2. Participant 2

Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 Set 7 Set 8 Mean
Trial 1 3.93 3.54 4.38 3.61 3.91 3.73 3.84 3.82 3.84
Trial 2 4.28 3.90 3.80 3.65 3.95 4.35 4.12 3.75 3.97
Trial 3 4.02 4.09 3.71 3.59 3.41 3.22 3.23 3.48 3.59
Trial 4 3.64 3.36 3.04 3.11 3.33 3.50 3.75 3.63 3.42

Table 3. Participant 3

Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 Set 7 Set 8 Mean
Trial 1 3.38 3.53 3.51 3.86 3.33 3.51 3.61 3.58 3.54
Trial 2 3.91 3.87 3.38 3.53 3.40 3.84 3.88 4.16 3.74
Trial 3 3.67 3.77 3.29 3.63 3.49 3.35 3.40 3.62 3.52
Trial 4 4.38 4.04 3.62 3.46 3.46 3.28 3.49 3.59 3.66

Table 4. Participant 4

Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 Set 7 Set 8 Mean
Trial 1 4.93 4.36 3.92 3.89 4.15 4.25 4.30 4.08 4.25
Trial 2 3.84 3.99 4.23 3.65 3.31 3.67 3.74 3.26 3.71
Trial 3 3.15 3.55 3.66 4.17 3.16 3.25 3.88 3.68 3.56
Trial 4 4.11 3.83 3.83 3.56 3.45 3.82 3.39 3.38 3.67

Tables 5 to 8 indicate pre and post test results for body fat percentage, body weight and maximal box squat.

Table 5. Participant 1
Pre test Post test
% Body fat 18.5% 18.3%
Body weight 121kg 121kg
Maximal box squat 265kg 305kg

Table 6. Participant 2
Pre test Post test
% Body fat 12.3% 12.6%
Body weight 104kg 103kg
Maximal box squat 290kg 325kg

Table 7. Participant 3
Pre test Post test
% Body fat 15.8% 15.9%
Body weight 92kg 91kg
Maximal box squat 210kg 212.5kg

Table 8. Participant 4
Pre test Post test
% Body fat 19.5% 19.2%
Body weight 99kg 99kg
Maximal box squat 215kg 225kg

Results indicate that mean speed for all groups was maintained for all participants. Groups 1 and 2 using accommodating resistance bands maintained bar speed with greater loads at the top of the movement. This would indicate a greater rate of force development. Groups using bands showed a greater transfer to a maximal box squat that was a test of absolute strength. No change in body weight and body fat percentage was shown by all participants during the trial.

DISCUSSION
The hypothesis of the use of rubber bands with weight training will develop motor learning patterns at an increased rate was supported. In all participants, body weight and body fat composition did not vary throughout the study.
Thus indicating that changes in measured performance outcomes were due to neurological changes. Qualitative research was conducted with all participants, with the groups using bands reported an increased awareness of stabilization relating this to intrinsic feedback. They reported that consciously activating the stabilizer muscles of the core allowed for greater transfer in the absolute strength test. Thus motor learning patterns were developed to allow for a functional transfer improvement.
All participants maintained mean bar speed throughout the trial even when loads were increased. The group using the bands had increased loads at the top of the movement where the body is more biomechanical efficient ( Siff, 1999 ). The bands deloaded to loads under the control group once on the box. The emphasis was to sit back on the box to overload muscles of the posterior chain i.e. gluteal muscles, spinal erectors, hamstrings and hips, all of the important muscles for increasing jumping power ( Poliquin, 1997).
The increased eccentric loading of the bands allowed for a faster decent phase of the squat, and allowed an intense rapid dynamic response to occur. The recruitment of the myotatic stretch reflex was activated because of the increased eccentric loading. The increase of load throughout the movement causing stretch, dynamic fibers are responsible for response required for load compensation as to realize full potentialities for combining direct excitation in the service of motor control (Granit, 1970).
An important component being observed was thee rate of force development in the muscles that are vital to sporting prowess ( Siff, 1999). This is given as a measurement of explosive strength. In the ascent phase of the movement, the varying load made the participant aware to accelerate the load, allowing for an increased time under tension but a lesser deceleration phase of the movement because of the accommodating resistance (Siff, 1999 ).
Both groups used compensatory acceleration techniques where reversal, speed and acceleration were the main objectives. Group using the bands reported an increased awareness of core muscles by pushing the abdominal wall against the weight belt. If the participants did not do this, they found that they were using incorrect form and struggled to complete the lift.
The following constitutes limitations of the study, that the sample group was relatively small and recruitment of more participants could have proven beneficial. Also a longer trial period may have been more beneficial. Selecting participants from a varied background of different sports and performing transfer tasks relative to each sport would provide a greater insight to the efficiency to this method of training.
Future research should investigate this relationship between the development of motor learning patterns and the transfer to increased sporting performance. As for many sports the ability to change direction, increase rate of force development, speed and acceleration are important components to assist performance. The development of these motor patterns contributes to core stability that can be a major factor in injury prevention. Training the body to respond to greater loads as well as allowing the nervous system to adapt has been a component that is sometimes overlooked in strength and conditioning programs for athletes.