Sensitivity of Load-Velocity Measures for Detecting Fatigue During Smith-Machine Squats (SLV)

Istanbul Gelisim University

Status: Completed

Conditions: Neuromuscular Fatigue; Load-velocity Variables

Treatments: Other: Moderate-fatigue; Other: Control Protocol (No Training); Other: High-fatigue

Study type: Observational

Funder types: Other

Identifiers

NCT07307963

2024/04/67

Details and patient eligibility

About

The purpose of this study is to determine whether load-velocity (L-V) relationship variables (L0, v0, and Aline) are sensitive indicators of fatigue produced by different squat fatigue protocols. The study aims to answer how accurately these L-V measures reflect changes in performance, particularly changes in one-repetition maximum (1RM), after varying levels of induced fatigue. Twenty-eight resistance-trained men completed three sessions involving different fatigue protocols or no training. L-V variables measured before and after each protocol were compared. The findings will help determine whether L-V relationship parameters can be used as practical and sensitive tools for monitoring fatigue during resistance training.

Full description

This study investigates how different levels of fatigue influence the parameters of the load-velocity (L-V) relationship during the Smith-machine squat exercise. After an initial familiarization and baseline testing session used to establish 1-repetition maximum (1RM) and to perform a repetition-to-failure test at 70% 1RM, participants completed three separate experimental sessions. Each session implemented a distinct fatigue protocol, and all protocols were performed between two incremental loading tests to determine pre-session and post-session L-V profiles.

The moderate-fatigue condition consisted of five sets at 70% 1RM, with participants performing half of their maximal possible repetitions per set. The high-fatigue condition required five sets performed to volitional failure using the same relative load. A control condition with no exercise was also included to establish non-fatigue reference values. L-V variables of interest included L0, v0, and Aline (calculated as L0 × v0 / 2). These variables were compared across conditions to determine their responsiveness to increasing levels of fatigue and their association with changes in neuromuscular performance, particularly reductions in 1RM strength.

Enrollment: 28 patients

Sex: Male

Ages: 18 to 35 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

Healthy males aged 18-40 years.

Resistance-trained (minimum 2 years of regular lower-body resistance training and ≥2 sessions/week).

Able to perform a proper smith-machine back squat with correct technique.

1-RM smith-machine squat measurable and ≥ bodyweight (or specify threshold used in study).

No musculoskeletal injury of lower limbs or back in the past 6 months.

Not using performance-enhancing drugs or anabolic steroids for the past 12 months.

Willing and able to attend all testing and training sessions and provide written informed consent.

Exclusion criteria

Any cardiovascular, pulmonary, metabolic, or neurological disease contraindicating intense exercise.

Recent (≤6 months) lower-extremity or spinal surgery or acute injury.

Current musculoskeletal pain or injury that limits squat performance.

Use of medications that affect neuromuscular performance (e.g., systemic corticosteroids) or stimulant drugs.

Regular participation in structured lower-body rehabilitation programs.

Failure to complete familiarization or preliminary 1-RM testing.

Inability or unwillingness to provide informed consent or follow study procedures.

Trial design

28 participants in 3 patient groups

Control Condition

Description:

Control Protocol Arm: Participants completed no exercise between the pre- and post-session load-velocity tests.

Treatment:

Other: Control Protocol (No Training)

Moderate-Fatigue Protocol

Description:

Participants performed 5 sets of the Smith-machine squat at 70% of their 1RM, completing half of the maximum possible number of repetitions in each set. This protocol was designed to induce a moderate level of fatigue while avoiding complete muscular failure.

Treatment:

Other: Moderate-fatigue

High-Fatigue Protocol

Description:

In the high-fatigue protocol, participants performed five sets of Smith-machine squats at 70% of their 1RM, completing each set to muscular failure. In every set, participants continued lifting until they could no longer complete a full repetition with proper technique. This protocol was designed to induce a high level of neuromuscular fatigue and to test the sensitivity of load-velocity variables under maximal fatigue conditions.

Treatment:

Other: High-fatigue