ECSS Paris 2023: CP-AP04
INTRODUCTION: The three main movements in free weight training, known as "the big 3," are the squat (SQ), bench press (BP), and deadlift (DL). These are commonly incorporated in strength and bodybuilding routines, offering significant benefits in muscle strength, explosive power, and hypertrophy. Exercise science emphasizes the use of the 1RM (One-repetition Maximum) to base training intensity, noting that 1-5RM can significantly enhance muscle strength, while 6-12RM is more effective for muscle hypertrophy. This approach is often considered the "gold standard" for assessing dynamic strength. However, accurate 1RM testing presents high-intensity muscular challenges and a relatively higher risk of injury, particularly due to increased blood pressure and muscle damage during maximal effort[1]. Prior research has shown a highly correlated relationship between isometric strength, muscle mass, and muscle strength[2,3]. Therefore, this study aims to use the isometric mid-thigh pull (IMTP) and the skeletal muscle mass index (SMI) to predict 1RM for SQ, BP, and DL. This approach could help mitigate injury risks and reduce the time cost associated with testing. METHODS: Following IRB approval, 45 student athletes (11 males, 34 females; mean age 21±0.9 years, height 167.9±7.3 cm, weight 66.1±11.3 kg) from taekwondo, archery, and volleyball were recruited on campus. In laboratory environment, portable force plates (9260AA, Kistler, CH) and a body composition analyzer (H20B, InBody, KR) were used to measure SMI and IMTP, while barbell was used to measure parameters such as SQ, BP, and DL. The Shapiro-Wilk test was utilized to assess the normality of SMI distribution. Pearsons product-moment correlation was used to determine the interrelationships among the parameters, and multiple regression analysis was applied to identify strong predictors. RESULTS: The SMI was normally distributed (W=.992, p=.991). Significant correlations were observed between SMI and IMTP (r=.721, p<.001), DL (r=.745, p<.001), BP (r=.795, p<.001), and SQ (r=.57, p<.001). Significant correlations were also noted between IMTP and DL (r=.819, p<.001), BP (r=.783, p<.001), and SQ (r=.643, p<.001). Multiple regression analysis revealed that IMTP and SMI could explain 72.1% of the variance in DL 1RM (p<.001), 72.4% of the variance in BP 1RM (p<.001), and 43.7% of the variance in SQ 1RM (p<.001). CONCLUSION: This study discovered that SMI and IMTP together exhibit significant linear relationships with the 1RM for DL, BP, and SQ, enabling the establishment of reliable regression models. Further experimental validation is required to verify the discrepancies between the formulas and real-world scenarios. The formulas are as follows: DL = -14.928 + .459 * IMTP + 7.801 * SMI BP = -38.147 + .205 * IMTP + 6.964 * SMI SQ = 46.531 + .322 * IMTP + 4.62 * SMI [1]Niewiadomski et al. (2008). J Hum Kinet, 19, 109-120. [2]DAntona et al. (2006). J. Physiol, 570(Pt 3), 611-627. [3]De Witt et al. (2018). J. Strength Cond. Res, 32(2), 528-533.
Read CV Chung-Kai WangECSS Paris 2023: CP-AP04
INTRODUCTION: One repetition maximum (1RM) is one of the most reliable and widely used indicators of an individuals strength. The measurement of velocity during the concentric phase has facilitated the reduction of stress and fatigue caused by the 1RM test directly obtained or estimated by validated formulas for the lower and upper body before training. Nevertheless, the use of mean velocity during the concentric phase of the movement can be influenced by different factors that need to be addressed such as sex. Thus, this study aimed to examine the differences in velocity and power production in the 1RM of bench press and back squat exercises according to sex. METHODS: Eighty-five recreationally trained participants (age: 23.4±4.2 years; sex (female/male): 44/41; training experience: 2.7 ± 2.3 years and 4.4 ± 1.1 days/week of training) performed a progressive loading test of up to 1-RM in the bench press and back squat exercises in a Smith machine. Mean and peak velocity and power output were analyzed in male and female participants. Then, the cohort of males and females was classified according to performance as relatively strong and weak based on their relative 1RM for the concentric phase of bench press and back squat exercises. The median values of relative 1RM in both sexes were used as a cut-off to enable this discrimination. RESULTS: There was a significant difference between male and female participants in the relative 1RM (1RM/kg) in the bench press (1.16±0.19 vs: 1.05±0.16; P<0.001) and the back squat exercise (1.56±0.27 vs 1.41±0.28; P=0.008). In the bench press, compared to female, male participants reported higher mean velocity (23%; P=0.047), mean and peak power (26% and 23%; P<0.020). No statistically significant differences were found between male and female participants in the back squat exercise. Then, difference according to performance (strong vs weak) and sex revealed that in the bench press exercise, Vmean was lower in weak females than weak males (27%, P=0.032), an effect not found in strong participants. While in the back squat exercise, differences in Wmean and Wpeak were observed only when comparing strong and weak participants of both sexes (16% and 24%, P < 0.01, r > 0.76). CONCLUSION: The main finding of this study was that males performed the 1RM in the bench press exercise at a higher Vmean, Wmean and Wpeak than female participants. However, these differences were not found in the back squat exercise. In addition, a secondary sub-group analysis revealed differences in Vmean, Wmean and Wpeak according to sex and level of performance (strong vs. weak). These results suggest the existence of sex differences in velocity and power production during the 1RM exercise according to exercise type and training status.
Read CV Cesar Munilla GamoECSS Paris 2023: CP-AP04
INTRODUCTION: Coordination and strength are essential to perform technical gestures during training and competition. These motor tasks are connected to the prefrontal cortex (PFC) response since the decision to maintain exercise is affected by sufficient blood flow and oxygenation supply for brain function. Cerebral hemoglobin consumption during high loads in strength exercises may change until failure in response to fatigue. Our study goal was to analyze cerebral hemoglobin consumption during two maximal protocols in the back squat exercise. METHODS: Twelve men (29.2 ± 4.3 years; 81.5 ± 2.2kg; 1.72 ± 0.19m) performed 6 (6RM) and 10 (10RM) repetitions until failure in back squat, with 72h of rest between. PFC response was analyzed by NIRS to measure the concentration of oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), total hemoglobin (tHb), and tissue oxygenation index (TOI). The first and last repetitions were analyzed in both protocols (6RM and 10RM) to understand the PFC responses up to failure (last repetition of both protocols) and non-failure (first repetition of both protocols) efforts. RESULTS: O2Hb was higher in 6RM than in 10RM in the first (8.12 ± 2.5 vs 5.41 ± 3.3 µmol/L) and last repetition (16.5 ± 5.5 vs 7.7 ± 4.5 µmol/L). No differences were observed in HHb and TOI between protocols. tHB incresed in both protocols from the first until the last repetition (6RM: 6.53 ± 2.2 µmol/L - 14.93 ± 5.27 µmol/L; 10RM: 3.41 ± 2.16 µmol/L - 6.01 ± 2.77 µmol/L ). O2Hb was higher in the last repetition than in the first one for both protocols (p<0.05). CONCLUSION: Increasing fatigue during 6RM and 10RM promoted a progressive increase in HbO2 and tHB response until failure being higher with heavier loads.
Read CV Luis LeitaoECSS Paris 2023: CP-AP04