Author(s): WANG, C.K., YU, T.A., HE, C.S., Institution: NATIONAL CHUNG CHENG UNIVERSITY, Country: TAIWAN, Abstract-ID: 567

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.