Influence of Loads and Loading Position on the Muscle Activity of the Trunk and Lower Extremity during Squat Exercise

Lower Body Weightlifting Injuries Treated in United States Emergency Departments from 2012-2021

Weightlifting has become an increasingly popular form of exercise that has been shown to have many health benefits but can be dangerous if performed improperly. The objective of this study was to describe the epidemiology of lower body weightlifting injuries in the United States. The National Electronic Injury Surveillance System database was queried from January 1, 2012, to December 31, 2021, for lower body injuries related to using weightlifting equipment. Demographics, diagnosis, disposition, and mechanism of injury (MOI) were analyzed. There were 7,773 lower extremity weightlifting injuries identified from 2012-2021, giving a national estimate of 311,842 injuries. The most common MOI was dropped weight (n=1785, 22.96%). Deadlifts were the most cited exercise that led to lower extremity injury (n=503, 6.47%). Males were more likely than females to be injured (76% males vs. 24% females; p<0.001), especially by compound movements with free weights including squats (79.63% males vs. 19.96% females, p<0.03) and deadlifts (83.89% males vs. 16.10% females, p<0.001). Nearly all injuries were treated as outpatient but those admitted to the hospital were significantly older than those treated as outpatients (38.0 years vs. 31.2 years, p<0.05). Weightlifting carries a high risk of injury due to the intensity and technique required for the different movements involved.

Full-Body Harness versus Waist Belt: An Examination of Force Production and Pain during an Isoinertial Device Maximal Voluntary Isometric Contraction

BACKGROUND/OBJECTIVES

This study examined the differences in participant force production and pain between a squat maximal voluntary isometric contraction (IMVIC) performed with either a waist belt (WB) or full-body harness (FBH) on the Desmotec D.EVO isoinertial device (D.EVO). Agreement between FBH IMVIC and a traditional force plate squat MVIC (TMVIC) was also assessed.

METHODS

Twenty adults completed FBH, WB, and TMVIC assessments on two separate occasions. Two-way treatment x time ANOVAs were conducted to compare force outputs and pain between treatments (FBH vs. WB) across time. Test-retest reliability was assessed using intraclass correlation coefficients. Associations between outcomes were determined using Pearson's r. Standard error of estimate, constant error, total error, and Bland-Altman plots were used to assess agreement between IMVIC and TMVIC.

RESULTS

FBH and WB IMVIC exhibited good to excellent reliability (ICC2,1 = 0.889-0.994) and strong associations (r = 0.813 and 0.821, respectively) when compared to TMVIC. However, agreement between FBH and TMVIC was poor. No significant interaction or main effects were observed for pain. FBH maximum isometric force (MIF) was significantly higher than WB MIF. WB IMVIC was the only significant predictor of TMVIC (R2 = 0.674).

CONCLUSIONS

Our findings indicate that the D.EVO should not be utilized as a replacement for a traditional MVIC setup.

The Limitations of Anterior Knee Displacement during Different Barbell Squat Techniques: A Comprehensive Review

Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.

Investigation of Structural Changes in Rectus Abdominis Muscle According to Curl-Up Angle Using Ultrasound with an Extended Field of View

The rectus abdominis (RA) muscle is related to abdominal muscle contraction and is divided into three sub-sections. In this study, changes in each section according to the curl-up angles were measured using ultrasound with an extended field of view (EFOV) scan and compared with the conventional scan. The results showed that the locations of the measurement position center were consistently detected only with the EFOV scan and that the change ratios in thickness and length between sections at the same angles were not significantly different, suggesting that each section was selectively activated. Furthermore, the ratios of the thickness and length changes in each section were significantly different between the rest position and curl-up angles. Specifically, in the section 2 there was a significant difference in the thickness and length changes between different angles, reflecting the characteristics of RA during contraction, and their variations were less than in the section 3. Therefore, the results suggest that changes in only a section of RA cannot be representative of overall RA activation, EFOV scan method can be useful for investigating the structural characteristics of RA in detail, and the proposed method can obtain various information about muscle contraction for efficient muscle treatment and muscle strengthening.