Greater squat stance width alters three-dimensional hip moment demands.

Barbell squat exercise may be performed with different stance widths, which will influence lower limb kinematics and joint reaction forces. Consequently, three-dimensional hip moments may vary with stance width, influencing muscle loading, and the muscles trained when performing squat exercise. To examine how squat stance width affects hip moments, males (n = 11) and females (n = 13) performed barbell squats at narrow, medium, and wide stance widths.

"Knees Out" or "Knees In"? Volitional Lateral vs. Medial Hip Rotation During Barbell Squats.

Chiu, LZF. "Knees out" or "Knees in"? Volitional lateral versus medial hip rotation during barbell squats. J Strength Cond Res 38(3): 435-443, 2024-Medial or lateral hip rotation may be present during barbell squats, which could affect the hip frontal and transverse plane moments.

Regulatory Light-Chain Phosphorylation During Weightlifting Training: Association With Postactivation Performance Enhancement.

Chiu, LZF, Fry, AC, Galpin, AJ, Salem, GJ, and Cabarkapa, D. Regulatory light-chain phosphorylation during weightlifting training: association with postactivation performance enhancement. J Strength Cond Res 37(10): e563-e568, 2023-Postactivation performance enhancement has been reported for multijoint resistance exercise, with both neural and intrinsic muscle mechanisms suggested as contributing factors.

Effect of incline versus block heel-raise exercise on foot muscle strength and vertical jump performance - an 11-week randomized resistance training study.

Strengthening the toe flexors and ankle plantar flexors may improve vertical jump performance. One exercise that may be effective for concurrently strengthening these muscles is heel-raises performed on an incline. The purpose of this study was to investigate the effects of incline versus conventional (block) heel-raise exercise on hallux and II-V digit flexor strength, vertical jump performance, and ankle plantar flexor strength.

Correcting for heel lift reduces ankle joint operating range for the ankle plantar flexor strength curve.

The ankle plantar flexor muscles are stronger in ankle dorsiflexion than plantar flexion. However, heel lift is commonly observed during ankle plantar flexor strength testing, a phenomenon that would alter ankle angle. The effect of heel lift on the relation between ankle angle and plantar flexor strength has largely been ignored.

Comparison of Alternative Methods to Improve Weight-Bearing Sagittal Plane Anterior Leg Rotation.

vonGaza, GL, and Chiu, LZF. Comparison of alternative methods to improve weight-bearing sagittal plane anterior leg rotation. J Strength Cond Res 35(12): 3315-3321, 2021-Promoting rearfoot plantar flexion may permit greater sagittal plane anterior leg rotation in weight-bearing tasks.

Assessment of countermovement jump with and without arm swing using a single inertial measurement unit.

The countermovement vertical jump height, flight time, and jump duration are used to assess athletic performance. Force-plate and motion-capture cameras are used to estimate these parameters, yet, their application is limited to dedicated lab environments. Despite the potential of inertial measurement units (IMU) for estimating the jump height, their accuracy has not been validated.

Knee Extensor Strength in Anterior Cruciate Ligament-Deficient Individuals Following Normal and Modified Squats: A Randomized Controlled Trial.

Jean, LMY, Gross, DP, and Chiu, LZF. Knee extensor strength in anterior cruciate ligament-deficient individuals following normal and modified squats: a randomized controlled trial. J Strength Cond Res 36(1): 47-54, 2022-Training with barbell squats, which load the quadriceps, increases knee extensor strength.

Midfoot and Ankle Mechanics in Block and Incline Heel Raise Exercises.

Chiu, LZF and Dæhlin, TE. Midfoot and ankle mechanics in block and incline heel raise exercises. J Strength Cond Res 35(12): 3308-3314, 2021-Although the heel raise exercise is performed to strengthen the calf muscles, the combination of calf muscle and ground reaction forces elicits moments that may deform the foot's longitudinal arch.

Three-dimensional modelling of human quadriceps femoris forces.

Quadriceps intramuscular anatomy is typically described in two dimensions. However, anatomical descriptions indicate fascicles in the quadriceps may have a three-dimensional orientation. The purpose of this investigation was to quantify the maximum force generating capacity of the individual quadriceps' muscles in three dimensions.

Elevating the Noninvolved Limb Reduces Knee Extensor Asymmetry During Squat Exercise in Persons With Reconstructed Anterior Cruciate Ligament.

Jean, LMY and Chiu, LZF. Elevating the noninvolved limb reduces knee extensor asymmetry during squat exercise in persons with reconstructed anterior cruciate ligament. J Strength Cond Res 34(8): 2120-2127, 2020-Anterior cruciate ligament (ACL)-injured individuals use less knee extensor net joint moment (NJM) in the involved vs.

A multiple fascicle muscle force model of the human triceps surae.

Muscle is typically modelled using a lump sum idealization, scaling a single fascicle to represent the entire muscle. However, fascicles within a muscle have unique orientations, which could result in forces exerted not only in the axis running along the tendon, but also the two perpendicular axes, describing the muscle's width and depth. The purpose of this research was to develop a geometric-based model of the soleus, medial gastrocnemius, and lateral gastrocnemius as distributed force systems which can predict three-dimensional forces.

Forefoot and heel take-off strategies result in different distribution of lower extremity work during landings.

Previous research suggests that landing mechanics may be affected by the mechanics of the preceding jump take-off. The purpose of the present study was to investigate whether jump take-off mechanics influence the subsequent landing mechanics. Female volleyball (n = 17) and ice hockey (n = 19) players performed maximal vertical jumps with forefoot and heel take-off strategies.

Analysis of different volleyballs' collision mechanics across a range of incident velocities.

Volleyball involves low-to-high-velocity collisions between the ball and a player. This research examined the kinematics, energetics and impact forces during collisions of different volleyballs across a range of incident velocities. Seven volleyball types were projected downwards between 8 and 30 m/s, impacting on a force platform.

Distribution of lower extremity work during clean variations performed with different effort.

The purpose of this research was to investigate how lower extremity work was distributed during the pull of cleans performed lifting the barbell to the minimum height required to receive it in a full squat (minimal height clean); or with maximum effort to elevate the barbell as high as possible and receiving it in either a full (maximal effort clean) or partial (power clean) squat. Eight weightlifters screened for proficient technique performed these clean variations at 80% of one repetition maximum. Work performed on the barbell and by the lower extremity net joint moments (NJM) was computed from marker trajectories and ground reaction forces.

Biomechanical Methods to Quantify Muscle Effort During Resistance Exercise.

Chiu, LZF. Biomechanical methods to quantify muscle effort during resistance exercise. J Strength Cond Res 32(2): 502-513, 2018-Muscle hypertrophy and strength adaptations elicited by resistance training are dependent on the force exerted by active muscles.

Addition of Glute-Ham-Gastroc Raise to a Resistance Training Program: Effect on Jump Propulsion and Landing.

Chiu LZF, Yaremko A, and vonGaza GL. Addition of glute-ham-gastroc raise to a resistance training program: effect on jump propulsion and landing. J Strength Cond Res 31(9): 2562-2571, 2017-Exercises such as squats and cleans are commonly used in resistance training programs to enhance athletic performance.

Enhancing Digital Video Analysis of Bar Kinematics in Weightlifting: A Case Study.

Weightlifting technique can be objectively assessed from two-dimensional video recordings. Despite its importance, participants' bar trajectories in research involving the snatch or clean exercises are often not reported, potentially due to the time required to digitize video. The purpose of this investigation was to evaluate the use of a light-emitting diode (LED)-based marker, digital video, and open-source software to automatically track the bar end during weightlifting exercises.

Changes in resting mitogen-activated protein kinases following resistance exercise overreaching and overtraining.

Purpose: Many physiological maladaptations persist after overreaching and overtraining resistance exercise (RE). However, no studies have investigated changes in mitogen-activated protein kinases (MAPK) after overtraining in humans, despite their critical role regulating exercise-induced muscular adaptations. The purpose of this study was to describe the changes in total and resting phosphorylation status of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun NH-terminal kinase (JNK) and p38-MAPK following a period of RE overreaching or overtraining.

Do Lower-Body Dimensions and Body Composition Explain Vertical Jump Ability?

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, Paquette, MR, and Relyea, GE. Do lower-body dimensions and body composition explain vertical jump ability? J Strength Cond Res 30(11): 3073-3083, 2016-Vertical jump (VJ) capability is integral to the level of success attained by individuals participating in numerous sport and physical activities. Knowledge of factors related to jump performance may help with talent identification and/or optimizing training prescription.

Net joint moments and muscle activation in barbell squats without and with restricted anterior leg rotation.

Muscle utilisation in squat exercise depends on technique. The purpose of this study was to compare net joint moments (NJMs) and muscle activation during squats without and with restricted leg dorsiflexion. Experienced men (n = 5) and women (n = 4) performed full squats at 80% one repetition maximum.

Consistency of Lower-Body Dimensions Using Surface Landmarks and Simple Measurement Tools.

Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, and Paquette, MR. Consistency of lower-body dimensions using surface landmarks and simple measurement tools. J Strength Cond Res 30(9): 2600-2608, 2016-Body dimensions may influence various types of physical performance.

Calcaneal Plantar Flexion During the Stance Phase of Gait.

When the rear- and forefoot are constrained, calcaneal plantar flexion may occur, deforming the longitudinal arch. Previous research has reported calcaneal motion relative to the tibia or forefoot; these joint rotations may not accurately describe rotation of the calcaneus alone. This investigation: (1) characterized the calcaneus and leg segment and ankle joint rotations during stance in gait, and (2) described the range of calcaneal plantar flexion in different structural arch types.

Quadriceps effort during squat exercise depends on hip extensor muscle strategy.

Hip extensor strategy, specifically relative contribution of gluteus maximus versus hamstrings, will influence quadriceps effort required during squat exercise, as hamstrings and quadriceps co-contract at the knee. This research examined the effects of hip extensor strategy on quadriceps relative muscular effort (RME) during barbell squat. Inverse dynamics-based torque-driven musculoskeletal models were developed to account for hamstrings co-contraction.

Proximal-to-distal sequencing in vertical jumping with and without arm swing.

Vertical jumping performance is dependent on muscle strength and motor skill. An understanding of motor skill strategies and their influence on jumping mechanics provides insight into how to improve performance. This study aimed to determine whether kinematic sequencing strategy influenced jump height, the effect of sequencing on jumping mechanics, and whether arm swing influences sequencing strategy.