Load-velocity Variables, Neuromuscular Fatigue
Conditions
Keywords
resistance training, fatigue, velocity-based training
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.
Detailed 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.
Interventions
OTHERControl Protocol (No Training)
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.
OTHERModerate-fatigue
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.
OTHERHigh-fatigue
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.
Sponsors
Istanbul Gelisim University
Study design
Observational model
CASE_CROSSOVER
Time perspective
CROSS_SECTIONAL
Eligibility
Sex/Gender
MALE
Age
18 Years to 35 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Theoretical Maximal Load (L0) Derived From the Load-Velocity Relationship | Baseline (pre-session) and immediately post-session (within 15 minutes) | Difference in theoretical maximal load (L0, kg) derived from the load-velocity relationship between baseline (pre-session) and immediately post-session incremental loading tests. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Theoretical Maximal Velocity (v0) Derived From the Load-Velocity Relationship | Baseline (pre-session) and 15 minutes post-session | Difference in theoretical maximal velocity (v0, m/s) derived from the load-velocity relationship between baseline (pre-session) and immediately post-session incremental loading tests. |
| Change in Area Under the Load-Velocity Relationship Line (Aline) | Baseline (pre-session) and immediately post-session (within 15 minutes) | Difference in area under the load-velocity relationship line (Aline, calculated as L0 × v0 / 2) between baseline (pre-session) and immediately post-session incremental loading tests. |
| Change in One-Repetition Maximum (1RM) in the Smith-Machine Squat | Baseline (pre-session) and immediately post-session (within 15 minutes) | Difference in one-repetition maximum (1RM, kg) in the smith-machine squat between baseline (pre-session) and immediately post-session incremental loading tests. |
Countries
Turkey (Türkiye)
Outcome results
None listed