Acute effects of isoinertial resistance application on sprint , vertical and horizontal jump performance

Purpose: The purpose of this study was to investigate of the acute effects of isoinertial resistance application on sprint, vertical and horizontal jump performance. Material: Volunteered 32 male students were divided into randomized experimental group and control group. Before and after 4-repetition maximal back squat with (for experimental group) or without isoinertial resistance application (for control group), 30 m sprint, vertical squat and countermovement jump tests with both legs, dominant leg, and non-dominant leg, standing broad jump and standing broad countermovement jump tests with both legs were assessed. Wilcoxon t test for preand post-test differences within the group, and Mann Whitney U test for preand post-test differences between the groups were used. Results: There were no significant differences within the group and between the groups for 30m both legs sprint parameters except pre-test mean stride length between the groups (Z=-2.27; p<0.02). Control group had a significant difference between preand post-test dominant leg vertical force (Z=-2.07; p<0.05). There were significant group differences in pre-test non-dominant leg countermovement jump (Z=-2.13; p<0.05), preand post-test non-dominant leg stride length (Z=-1.99 and Z=-2.28; p<0.05, respectively). Conclusions: As a result of the effect of acute isoinertial resistance application to stride length especially to non-dominant stride length it is concluded that long-term isoinertial resistance training can support sprint performance with tolerating stride length imbalance between dominant leg and non-dominant leg.

Introduction 1  Since force and force production of neuromuscular system is critically important for high level performance in each sport event, most appropriate training methods are determined to develop power [1].Isoinertial eccentric training system that develops motor coordination based on proprioception, balance, neuromuscular efficiency and posture control by developing neuromuscular activity and that becomes one of the popular training methods is a technology that reveals equal amount of eccentric force against concentric force (isoinertial) applied by athletes [2].Since it is short and high intensity training, this training will increase power of athletes by enabling force and speed in muscle activities [3] and compared to weight training in eccentric muscle contraction, it provides higher muscle activation [4].Therefore, it was determined that isoinertial strength, speed, and force relation for maximal power helped identification of responsible mechanism and training adaptation [5].
Maximal power can be developed by increasing skills to develop high level of force in given speed and/ or showing given force at higher speed [6].Isoinertial strength training reacts produced concentric force with constant eccentric resistance and enables development on unit power and explosive power by enabling contraction at muscle elongation phase.In optimally overloaded strength training, half squat and squat jump (SJ) are important movements to prevent force and speed decreases [7].Wisløff et al. [8] stated that amount of weight in a maximum half squat is highly related with acceleration and vertical jump (VJ).Additionally, VJ is generally used for evaluation isoinertial leg power since it includes simple and explosive movements [6].
VJ and horizontal jump (HJ), including sequences of complex movements, are related with leg muscle strength, explosive power, flexibility of muscles in vertical or horizontal jump as well as vertical and horizontal jump techniques.To provide an effective VJ or HJ, during application of the jump technique, joints should be flexion in proper angles.Maximal muscle contraction during extension and explosive application of the movement increases efficiency of VJ and HJ [9].Height performed in VJ and distance performed in HJ evaluates leg power and these are closely related with speed performance [10].Maulder et al. [11] found statistically significant positive relationships among horizontal force (HF), vertical force (VF), and sprint velocity.Different jump tests are applied to test different strenght qualities.Squat jump (SJ) evaluates leg explosive power under concentric conditions while countermovement jump (CMJ) measures leg power under slow stretch shortening cycle and low stretching overload conditions [12].Due to stretch shortening cycle organised by high level of active movement during eccentric phase of CMJ stated by Cormie et al. [13], the most general dynamic performance test for neuromuscular fatigue during isoinertial resistance load is CMJ test [14].HJ requires both horizontal and vertical propulsive force and this enables analysing activities that contain linear movements in horizontal plane [15].However, there are limited number of studies to determine horizontal functional performance relationships.Nagona et al. [16] determined that during an active movement in standing broad jump (SBJ) by moving centre of mass to forward effectively, there were more effective mechanical energy transfer and high level muscle activations based on hip flexion of muscles such as rectus femoris.Therefore, such plyometric jumps that can be considered as elastic power with maximal strength and indicates high relationships with muscle fiber type, contraction speed, metabolic properties of muscle, neuromuscular activation, and kinetic energy transfer.
Sprint and jump require eccentric strength plays an important role to develop performance [17].Eccentric strength training with isoinertial resistance training system will increase power by enabling force and speed as the muscle activitation [3] and compared to traditional weight training it provides higher muscle activation [4].This supports that isoinertial resistance training will be a more effective training for development of HF and VF during sprint, VJ height performed during SJ and CMJ, HJ distance performed during standing broad jump (SBJ) and standing broad countermovement jump (SBCMJ).Thus, the purpose of the currrent study was to investigate acute effects of isoinertial resistance application on sprint, VJ, and HJ performance.Procedures Subjects participated in tests and squat workouts for trial and familiarization between the hours of 9.30 and 11.00 one week before the study.Additionally, EG participated in squat workouts with isoinertial resistance application.After 20min warm-up consisting of light tempo running, flexibility, and calistenic exercises, 2x30m sprints with 3-min interval were tested on non-motorised treadmill.Based on both leg (BL), dominant leg (DL), and non-dominant leg (NDL) that sprint parameters stride frequency (SF), stride length (SL), HF, VF, work (W) and power (P) were determined.As stated by Kaçoglu and Kale [18], VJ and HJ tests were applied after 90 sec passive rest.Pre-tests were completed 2 reps SJ, CMJ based on BL, DL, and NDL, SBJ and SBCMJ based on BL with 30sec interval between reps and 60sec passive rest between tests.Statistically better result of 2 trials for each jump were evaluated.After three days of break, before post-test, both groups applied 4-RM half squat workout with BL and 3min passive rest was applied at the end.EG applied the workout with isoinertial resistance with isoinertial strength training system.After passive rest, tests were repeated with same protocols.

Isoinersial Resistance Application Program
While the subject was straight and parallel to wall, his elbows were bent 90º, hands on waist, eyes looking forward, femur of each leg parallel to ground, and 90º knee angle, with isoinertial training system (Desmotec D11-V12 Version Sport Pro, Italy) linked to his waist with an adjustable rope, subjects applied 4-repetition maximal (4 RM) half squat workout.Power values from isoinertial resistance application are shown in Table 1.

551±290 507±246
Sprint Test Subjects were participated to 2x30 m sprint test with 3 min intervals on non-motorised treadmill (Woodway Force 3.0, Woodway Inc., USA) after 20 min warmup consisting of light tempo running, flexibility, and calistenic exercises.Before testing, HF strain gauge was adjusted parallel to treadmill based on the waist level.Thirty meter sprint speed was calculated with (V mean )= distance (d)/time (t) in terms of m.sn -1 .During 30 m sprint, mean HF (HF mean ) and mean VF (VF mean ) data were recorded to computer at 200 Hz.The best 30 m sprint result was statistically analysed.HF mean was calculated with 30 m sprint total HF/30m sprint total stride number formula in terms of Newton.VF mean was calculated with 30 m sprint total VF/30m sprint total stride number formula in terms of Newton.Same calculation method was used for all other sprint parameters of both legs that are mean SF (SF mean ), mean SL (SL mean ), mean W (W mean ) and mean P (P mean ), and also DL and NDL that are dominant leg SF (SF DL ), non-dominant leg (SF NDL ), dominant leg SL (SL DL ), non-dominant leg SL (SL NDL ), dominant leg HF (HF DL ), non-dominant leg HF (HF NDL ), dominant leg VF (VF DL ), non-dominant leg VF (VF NDL ), dominant leg W (W DL ), non-dominant leg W (W NDL ), dominant leg P (P DL ), non-dominant leg P (P NDL ).
Vertical Jumps SJ and CMJ tests based on BL, DL, NDL [both leg SJ (SJ BL ), dominant leg SJ (SJ DL ), non-dominant leg SJ (SJ NDL ), both leg CMJ (CMJ BL ), dominant leg CMJ (CMJ DL ), non-dominant leg CMJ (CMJ NDL ),] were applied to participants as VJ.To transfer data of jumping mat acted as electronic on-off switch to 1000Hz computer, ESC 2XXX Series Data Acquisition computer software (Tümer Elektronik Ltd, Ankara, Turkey) was used and flight time of SJ and CMJ in BL, DL and NDL were PEDAGOGICS PSYCHOLOGY transferred to computer.After each VJ test, subjects rested for 60 sec.For each VJ test, 2 trials were conducted with 30 sec interval and higher jump height was considered for statistical evaluation.Each jump height was calculated with the formula adopted by Bosco et al. [19]: h= g.t f 2 .8 - 1 .100where h-is the jump height (cm), g-is gravitational acceleration (9.81 m.s -2 .),t f is flight time (s).SJ was applied as vertical jump where feet were at shoulder width, eyes are focused straight, hands on waist, and waiting stable squat position (85-90º knee angle) for 2-3 sec while CMJ was applied on the same mat where feet were at shoulder width, eyes are focused straight, hands on waist, and squating in shortest time possible from the standing position to on knees (85-90º knee angle).
Horizontal Jumps SBJ and SBCMJ tests based on BL were conducted as HJ test.SBJ was applied as broad jump where feet were at shoulder width, eyes are focused straight, hands on waist, and waiting stable squat position (85-90º knee angle) for 2-3 sec while SBCMJ was applied as broad jump where feet were at shoulder width, eyes are focused straight, hands on waist, and squating in shortest time possible from the standing position to on knees (85-90º knee angle).Distance between toe tip before broad jump and heel after broad jump was measured with a steel meter (Stabila, Germany) and recorded as cm.After each horizontal jump test, participants rested for 60 sec.For each horizontal jump test, 2 trials were conducted with 30 sec interval and the longer jump distance was considered for statistical evaluation.
Statistical Analysis Data analysis was conducted with SPSS 22 (SPSS Inc., Chicago, IL, USA).After determining mean, standard deviation, and percentage change, intra-group pre-test and post-test percentage changes were determined.Intragroup pre-and post-test results compared with Wilcoxon T test, and inter-group pre-and post-test results compared with Mann Whitney U test.Significance level was selected as p<0.05.

Results
As seen from Table 2, there were no statistically significant difference for all intra-group pre-and post-test results of VJ and HJ parameters of EG and CG.Except the post-test result of CMJ NDL (Z= -2.13; p<0.05), there were no statistically significant differences for inter-group results of VJ and HJ parameters.When intra-group preand post-test% percentage was analysed, it was shown that VJ and HJ parameters were changed in between -9.3 and -0.5% for EG, between -6.6 and 0.5% for CG.
As seen from Table 3, there were no statistically significant differences between intra-group pre-and posttest V mean , SF mean , SL mean , HF mean , VF mean , W mean and P mean results of BL sprint parameters.There was a statistically significant difference for inter-group pre-test results of SL mean (Z= -2.27; p<0.02).There were no statistically significant inter-group differences in pre-and post-test V mean , SF mean , HF mean , VF mean , W mean ve P mean results of BL sprint parameters.In EG, except VF mean (2.1%), all other BL sprint parameters showed negative change between -1.2 and -2.7%.In CG, except HF mean and VF mean (-0.5% and -1.5% respectively), all other BL sprint parameters showed positive change between 0.7 and 1.9%.
As seen from Table 4, there were no statistically significant intragroup differences between pre-and posttest DL and NDL sprint parameters of EC and GC, except statistically significant difference for VF DL parameter (Z=-2.07;p<0.05) of CG.In terms of inter-group pre-and post-test SL NDL results, there were statistically significant differences (for pre-test Z=-1.99 and for post-test Z=-2.28; p˂0.05) but there were no statistically significant differences for SL DL parameter.For W NDL results, there was only statistically significant inter-group pre-test difference (for pre-test Z=-2.22; p<0.03).Among EG preand post-test DL and NDL results, the highest changes were in W DL parameter with 6.6% positive change and in W NDL parameter with -6.6% negative change.Among CG pre-and post-test DL and NDL results, the highest changes were in W NDL parameter with 2.8% positive change and in VF DL parameter with -6.6% negative change.

Discussion
In this study, all VJ and HJ parameters of EG and CG which were SJ BL , SJ DL , SJ NDL , CMJ BL , CMJ DL , CMJ NDL , SBJ and SBCMJ showed no statistically significant differences for intra-group pre-and post-test results.However, when percentage changes were analysed, there were decreasing trends in all pre-and post-test results of EG.For VJ, Howatson et al. [20] found that CMJ BL was unchanged one day after isoinertial load application.Kennedy and Drake [21] determined that right after isoinertial resistance aplication, CMJ BL statistically decreased (p<0.05)(36.1±0.78 cm vs. 32.4±0.74cm).In current study, there was no statistically significant difference, however, CMJ BL decreased from 38.3±5.6 cm to 36.6±3.9 cm.The jump test 3 min after isoinertial power application may be a factor causing such a difference.Sequence of motor unit recruitment in voluntary muscle contraction is from small motor unit to large motor unit based on intensity of stimulus and sub-maximal voluntary muscle contraction only recruites small motor units of muscle.During an eccentric contraction that contains maximal or supra-maximal contractions that cause recruitment of large motor units, elastic energy is stored in serial elastic elements and is used during concentric contraction where contractile elements and serial elastic elements shorten [22].For the activation that has a concentric contraction during SJ, more time is required for activation in CMJ that contain a concentric contraction right after an eccentric contraction [23].Therefore, with

PEDAGOGICS PSYCHOLOGY
preliminary overload effect in CMJ, eccentric contraction caused an increase muscle force at the beginning of concentric contraction [24].Jakobsen et al. [17] showed that eccentric force training of hamstrings muscle group, recruited large motor units, positively increased eccentric force related performance development such as VJ and HJ.Nosaka et al. [25] stated that force production of an eccentric contraction is 5 times more than force producted of a concentric contraction.Vazquez-Guerreo and Moras [26] determined that since force of resistance in isoinertial system is dynamic, there is same or more force development than same movements with traditional weight training.Norrbrand et al. [4]  In this study, there were no statistically significant differences between intragroup pre-and post-test results of EG and CG for V mean , SF mean , SL mean , HF mean , VF mean , W mean , and P mean .These results indicate that 4 RM isoinertial resistance applicaiton had no acute effect on all sprint parameters but statistically significant intergroup pre-test difference (Z= -2.27; p<0.02) and no statistically significant post-test difference for SL mean indicated that in EG, 4 RM isoinertial resistance training had an acute effect.Accordingly, when SL was analysed for DL and NDL, intra-group and inter-group pre-and post-test results were compared for SL DL , there were no statistically significant differences.However, there were statistically significant intergroup differences for pre-and post-test results of SL NDL (Z= -1.99 and -2.28; p<0.05, respectively).Therefore, this shows that 4 RM isoinertial resistance application acutely effected SL NDL .Pre-and post-test results of EG, decreased SL DL (from 1.61±0.24mto 1.57±0.32m)and increased SL NDL (from 1.28±0.19mto 1.32±0.23m),indicated that this could help tolerating bilateral leg imbalance.When inter-group results were compared, while there was statistically significant pretest difference for W NDL (Z=-2.22;p<0.03), no statistically significant difference for post-test.In addition, increased W DL (from 181±40J to 193±46J) and decreased W NDL (from 254±48J to 237±74J) in pre-test and post-test of EG supports this idea.As stated by Chu and Korchemny [27], muscles are intensively contracted, relaxed, and strecthed during ballistic cyclic movements of sprint that absorb shocks and amortise external factors by moving body segments in different forms and range of motion accelerate or decelerate to balance joints and determine the best force application.Based on this force, SF and SL parameters of both legs are at optimum level.Therefore, while lower SF and higher SL was displayed in DL, higher SF and lower SL was displayed in NDL.Based on this, it is believed that high differences in SF, HF, VF, W, P, and especially SL could be eliminated or minimised in individuals with isoinertial resistance training based on 30m sprint in DL and NDL.
As a result of the effect of acute isoinertial resistance application to SL especially to SL NDL , it is concluded that long-term isoinertial resistance training can support sprint performance with tolerating SL imbalance between DL and NDL.In addition, statistically significant difference for intergroup CMJ NDL showed that isoinertial resistance application for CMJ NDL can develop NDL elastic power.

Table 2 .
Pre-and post-test results of vertical and horizontal jump parameters * Statistical significant pre-test inter-group difference, p<0.05.

Table 3 .
Pre-and post-test results of 30m BL sprint parameters * Statistical significant pre-test inter-group difference, p<0.05.

Table 4 .
Pre-and post-test results of 30m DL and NDL sprint parameters training for CMJ NDL can benefit to development of NDL elastic power.