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

NCT07307963 | Completed DMC

• 1 other identifier: 2024/04/67
• Study Type: observational
• Target: 28
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Neuromuscular Fatigue; Load-velocity Variables

Keywords

resistance training; fatigue; velocity-based training

Outcome Measures

Primary Outcomes (1)

• Change in Theoretical Maximal Load (L0) Derived From the Load-Velocity Relationship

  Difference in theoretical maximal load (L0, kg) derived from the load-velocity relationship between baseline (pre-session) and immediately post-session incremental loading tests.

  Baseline (pre-session) and immediately post-session (within 15 minutes)

Secondary Outcomes (3)

• Change in Theoretical Maximal Velocity (v0) Derived From the Load-Velocity Relationship

  Baseline (pre-session) and 15 minutes post-session

• Change in Area Under the Load-Velocity Relationship Line (Aline)

  Baseline (pre-session) and immediately post-session (within 15 minutes)

• Change in One-Repetition Maximum (1RM) in the Smith-Machine Squat

  Baseline (pre-session) and immediately post-session (within 15 minutes)

Study Arms (3)

Control Condition

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

Other: Control Protocol (No Training)

Moderate-Fatigue Protocol

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.

Other: Moderate-fatigue

High-Fatigue Protocol

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.

Other: High-fatigue

Interventions

Control Protocol (No Training) OTHER

This intervention consists of no training or exercise during the session. Participants assigned to the control arm rest for the entire duration between the pre-session and post-session load-velocity assessments. No fatigue-inducing activity, resistance exercise, or additional intervention is administered, allowing all observed changes to reflect normal variation without training-related fatigue.

Control Condition

Moderate-fatigue OTHER

Participants performed five sets of Smith-machine squats at 70% of their 1-repetition maximum (1RM), completing half of the maximum possible repetitions in each set. This protocol was designed to induce a moderate level of neuromuscular fatigue without reaching complete exhaustion.

Moderate-Fatigue Protocol

High-fatigue OTHER

This intervention involves no training or fatigue-inducing activity. Participants do not perform any squat sets between the pre- and post-session incremental loading tests. This condition serves as a baseline to determine natural variations in load-velocity measures, thereby eliminating the influence of exercise-induced fatigue.

High-Fatigue Protocol

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)
• Sampling Method: Probability Sample

Study Population

Twenty-eight physically trained males, with an average age of 23.3 years (standard deviation \[SD\]: 3.0 years; range: 20-36 years), willingly enrolled in this research endeavor. The participants exhibited a mean body mass of 78.1 kg (SD: 9.3 kg), a body height of 177.2 cm (SD: 3.3 cm), and a one-repetition maximum (1RM) for smith-machine squat (SMS) exercise of 150.9 kg (SD: 12.5 kg). All subjects possessed prior RT experience, averaging 5.0 years (SD: 2.6 years), and demonstrated proficiency in executing the SMS exercise during the familiarization session.

You may qualify if:

• 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.
• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Istanbul Gelisim University: lead

Study Sites (1)

İstanbul Gelişim Üniversity

Istanbul, avcılar, 34310, Turkey (Türkiye)

Location

MeSH Terms

Conditions

Fatigue

Condition Hierarchy (Ancestors)

Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Deniz Şentürk, PhD

  Istanbul Gelisim University

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: observational
• Observational Model: CASE CROSSOVER
• Time Perspective: CROSS SECTIONAL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor, PhD

Study Record Dates

• First Submitted: November 27, 2025
• First Posted: December 29, 2025
• Study Start: May 5, 2024
• Primary Completion: May 10, 2024
• Study Completion: October 10, 2024
• Last Updated: December 29, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR
• Time Frame: Individual participant data and supporting documents will become available 6 months after publication of the study results and will remain available for 5 years.
• Access Criteria: Individual participant data (IPD) will be shared in anonymized form with qualified researchers for scientific purposes. The shared data will include de-identified performance measurements, load-velocity variables, and outcome measures relevant to the study.

Locations

TU (1)