Professional power-oriented athletes, sprinters or individuals that performed regular sprint-power related or heavy resistance exercise will be excluded from our analysis. Only right-leg-dominant Southeast Asians (for ≥ 3 generations), with a Body Mass Index (BMI) mean 23 kg/m2, will be included to this study to ensure both body composition and genetic homogeneity.
Participants that answer ‘yes’ to any of the eight PAR-Q questions or suffered from medical conditions interfering with their ability to exercise such as high blood pressure, acute or chronic musculoskeletal injuries will be excluded from the study. Furthermore, the GPPAQ questionnaire, will be used to assess the current physical activity levels of our cohorts. Participants that will report to be involved in sprint-strength related leisure time activities such as tennis and gym workout or participants that their work involved vigorous activity including handling of very heavy objects (e.g. scaffolder, construction worker, refuse collector ect.) will be excluded from this analysis.
Participants will be asked to refrain from caffeine and alcohol during and before all tests. To ensure adequate access to carbohydrate energy stores, participants will be asked to consume an energy drink (1 to 1.5 g•kg − 1 BM) before the commencement of the testing session, according to Australian Institute of Sport (AIS) guidelines (https://www.ausport.gov.au/ais/sports_nutrition), composed of mainly liquids and carbohydrates.
2.1. STUDY OVERVIEW
One week before the tests, all participants will receive comprehensive instructions about the tests. Two hours prior to the test, participants will be asked to practice three types of jumps (SJ, CMJ & DJ) and one explosive sprint (Fig. 1a & 1b) in order to familiarize themselves before they perform 5 trials for each test as shown in study timeline in Fig. 2b.
SJ jumps will be executed starting from a parallel 90° feet alignment (Phase C), as shown in the Fig. 1a. The starting position of the knee angle will be measured with a handheld goniometer, followed by a restricted arm motion jump (Phase F2) according to the procedure described by (18, 19). For CMJ trails, the participants will start from the upright standing position (Phase L1) performing a preliminary fast downward movement by flexing their knees and hips (Phase E) and then immediately extend their knees & hips again (Phase C) to jump vertically up off the ground (Phase F2). For DJ jump trails, the participants will be standing on a 20 cm box (Phase D) and then they will to step off from the box (Phase F1) and immediately jump up vertically after touching the ground (Phases E, C and F2).
For the sprint test the participants will be asked to perform a 5-meter sprint between Gate A and Gate B, while they are captured by the cameras as shown in Fig. 1b. All participants will be encouraged to sprint as fast as possible.
Motion capture technology will be used for data collection and data analysis will be conducted by Qualisys Track Manager (QTM) software. Eleven reflective markers will be set on specific anatomical positions of the trunk and lower limbs. More specifically, one marker will be set on Sacrum (S), two reflective markers will be set on left and right anterior superior iliac spine (B), two markers will be set on left and right greater trochanter (C), two markers will be set on left and right lateral condyle (D), two markers will be set on left and right apex of the lateral malleolus (E) and two markers will be set on left and right 5th metatarsal (F) as it is indicated in Fig. 2a. For detecting the reflective markers accurately, the exposure, threshold, frequency and flash time of each of the nine cameras will be set accordingly.
When the markers reflection is not satisfactory the reflective’s marker exposure, threshold or flash time will be adjusted in order for the researcher to be able to view the reflection of the marker clearly on the screen. Before each testing session the equipment will be calibrated by the wand and L-shaped structure provided by the manufacturer.
The captured data from reflective markers (S) will be used for analyzing kinematic data such as peak velocity, acceleration, jump hight and running times. The captured data from reflective markers (B, C and D) will be used for calculating angular velocity and acceleration in hip joint while the captured data from reflective markers (D, E and F) will be used for the calculation of angular velocity and acceleration in knee joint. For the calculation of torque, in hip or knee joints we will use the following formula according to (20) and for segmental mass estimation we will follow the procedure described by (21).
Torque = Segmental mass in hip or knee joints x Angular acceleration
To measure force related dynamic data we will use a Bertec force-plate (90cm x 90cm) as shown in Fig. 2a. For the calculation of peak power and rate of force development we will use the following formulas according to (20).
Peak power = F (force production at peak velocity) x V (Peak velocity)
Rate of Force Development = Peak force / Time to peak force
2.2. GENETIC ANALYSIS
Few drops of blood (100–200 µl) will be obtained using a spring loaded blood lancet to pierce the skin of the subject’s fingertip. The DNA will be extracted from white blood cells using commercial DNA isolation kits. The procedure will be carried out at room temperature and the DNA (yield 10–20 µg) will be stored at -20 ˚C. Genotyping will be performed by polymerase chain reaction (PCR) using standard procedures.
2.3. SAMPLE SIZE AND STATISTICAL ANALYSIS
The proposed sample size (100 participants) is designed to yield enough power for hypothesis testing and to obtain reliable results. The calculation of sample size will be based on mean value and the standard deviation (mean ± SD) of the tested parameters derived from previous studies (16, 17). Appropriate statistical tests, with multiple comparisons, will be used for data analysis, using both the SPSS and the R packages. A p value will be considered as significant depending on the statistical test and number of tests. Multiple testing corrections will be applied accordingly. The significance for all tests will be set at 5% (p-value < 0.05). For the preliminary results, to compare the mean values between the female participants with ACTN3 RR + RX and ACTN3 XX genotypes we used a T-test. To check the normality we used by Kolmogorov Simonov test and the observed genotype counts were not statistically different for those expected under Hardy–Weinberg equilibrium (HWE).
2.4. RESULTS
A statistically significant peak angular acceleration (P = 0.01) was found in females between ACTN3 RR + RX (552.2 ± 72.2 deg/s) and ACTN3 XX (428.6 ± 109.3 deg/s) genotype groups during the eccentric phase of DJ jump in the left knee joint with differences in torque and power production, as indicated in Fig. 3. We detected no statistically significant differences in angular velocity and torque in either SJ or CMJ jumps.