Isometric vs. Dynamic Squat Pre-Loading: Acute PAPE Responses

NCT07696026 | Not Yet Recruiting

• 1 other identifier: UKarabuk-6
• Study Type: interventional
• Target: 22
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized crossover study compared the acute post-activation performance responses to isometric and dynamic squat-based preconditioning protocols performed with and without electromyostimulation (EMS). Participants completed five randomized experimental conditions: maximal voluntary isometric contraction (MVIC), dynamic contraction (DC), MVIC+EMS, DC+EMS, and EMS only (O-EMS). Baseline and post-intervention assessments included countermovement jump (CMJ), countermovement jump with arm swing (CMJWH), zig-zag agility, and shooting speed, with post-tests conducted after a 4-minute recovery period. Perceptual responses, including ratings of perceived exertion (RPE), perceived discomfort (RPD), and fatigue (VAS), were recorded immediately after each protocol. All sessions were conducted between 14:00 and 16:00 under standardized conditions, with protocol order randomized and participants instructed to avoid strenuous exercise and food intake before testing.

Conditions

Soccer; Performance; Contraction

Keywords

isometric contraction; dynamic contraction; squat; PAPE

Outcome Measures

Primary Outcomes (4)

• Countermovement Jump (CMJ) Height

  Change in countermovement jump (CMJ) height (cm) from baseline to 4 minutes after each conditioning protocol, measured using a jump assessment system.

  aseline and 4 minutes after each experimental condition

• Countermovement Jump with Arm Swing (CMJWH) Height

  Change in countermovement jump with arm swing (CMJWH) height (cm) from baseline to 4 minutes after each conditioning protocol.

  Baseline and 4 minutes after each experimental condition

• Zig-Zag Agility Performance

  Change in zig-zag agility performance time (s) from baseline to 4 minutes after each conditioning protocol.

  Baseline and 4 minutes after each experimental condition

• Shooting Speed

  Change in maximal shooting speed (km/h) from baseline to 4 minutes after each conditioning protocol, measured using a radar gun.

  Baseline and 4 minutes after each experimental condition

Secondary Outcomes (3)

• Rating of Perceived Exertion (RPE)

  Immediately after each experimental condition

• Rating of Perceived Discomfort (RPD)

  Immediately after each experimental condition

• Perceived Fatigue

  Immediately after each experimental condition

Study Arms (5)

Condition 1

EXPERIMENTAL

Dynamic contraction

Other: dynamic conraction

Condition 2

EXPERIMENTAL

isometric contraction

Other: isometric contraction

Condition 3

EXPERIMENTAL

Dynamic + EMS contraction

Other: dynamic and EMS contraction

Condition 4

EXPERIMENTAL

Isometric + EMS Contraction

Other: isometric and EMS conraction

Condition 5

EXPERIMENTAL

EMS contraction

Other: ems contraction

Interventions

dynamic conraction OTHER

Participants performed a dynamic back squat conditioning protocol on a Smith machine consisting of five sets of one repetition at 90% of one-repetition maximum (1RM), with 1 min of passive recovery between sets. Each repetition included a controlled descent to approximately 90° of knee flexion, an explosive concentric phase, a 2-s isometric hold at full knee extension, and a slow, controlled eccentric phase (Pincivero et al.). All repetitions were supervised to ensure proper technique. The protocol was selected based on previous evidence supporting high-intensity resistance exercise as an effective conditioning activity for inducing PAPE responses (Dobbs et al.).

Condition 1

isometric contraction OTHER

The isometric contraction protocol was conducted as described by Koźlenia and Domaradzki (2023) and Lim and Kong (2013). Participants assumed a squat position in a squat rack with the barbell fixed in place and the knee joint positioned at approximately 90° of flexion (Profitness 1030, Türkiye). The barbell was secured to the rack using safety pins, and participants were instructed to exert maximal force against the immovable bar to produce a MVIC. Each contraction lasted 3 seconds, and a total of 3 repetitions were performed with 2 min of rest between repetitions (Koźlenia \& Domaradzki, 2023; Lim \& Kong, 2013).

Condition 2

dynamic and EMS contraction OTHER

Participants performed a dynamic back squat conditioning protocol on a Smith machine consisting of five sets of one repetition at 90% of one-repetition maximum (1RM), with 1 min of passive recovery between sets. In the DC-EMS condition, electromyostimulation (EMS) was applied simultaneously throughout the conditioning protocol. Each repetition included a controlled descent to approximately 90° of knee flexion, an explosive concentric phase, a 2-s isometric hold at full knee extension, and a slow, controlled eccentric phase (Pincivero et al.). All repetitions were supervised to ensure proper technique. The protocol was selected based on previous evidence supporting high-intensity resistance exercise as an effective conditioning activity for inducing PAPE responses (Dobbs et al.).

Condition 3

isometric and EMS conraction OTHER

The isometric contraction protocol was conducted as described by Koźlenia and Domaradzki (2023) and Lim and Kong (2013). Participants assumed a squat position in a squat rack with the barbell fixed in place and the knee joint positioned at approximately 90° of flexion (Profitness 1030, Türkiye). The barbell was secured to the rack using safety pins, and participants were instructed to exert maximal force against the immovable bar to produce an MVIC. Each contraction lasted 3 seconds, and a total of three repetitions were performed with 2 min of rest between repetitions (Koźlenia \& Domaradzki, 2023; Lim \& Kong, 2013). In the MVIC-EMS condition, electromyostimulation (EMS) was applied simultaneously during each maximal voluntary isometric contraction.

Condition 4

ems contraction OTHER

EMS was delivered bilaterally to the quadriceps using a portable stimulator (Compex Rehab 400, Compex Medical SA, Switzerland) with a biphasic symmetrical rectangular waveform (75 Hz, 450 μs). Four self-adhesive electrodes were placed over the vastus medialis and vastus lateralis muscles of both legs. Participants remained seated for 10 min with the knees flexed at approximately 90° and the hips flexed at approximately 110°, while receiving EMS without performing any voluntary contractions. Stimulation intensity was gradually increased to the highest level tolerated by each participant and maintained throughout the intervention (Paillard et al., 2008; Sofuoğlu et al., 2025).

Condition 5

Eligibility Criteria

• Age: 18 Years - 25 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Being healthy
• Male volleyball athletes
• Willing to maintain the intervention for all sessions

You may not qualify if:

• Being under 18 years old
• Having a chronic disease
• Contraindications for exercise

Sponsors & Collaborators

• Karabuk University: lead

Study Sites (1)

Karabuk University

Karabük, Turkey, 78200, Turkey (Türkiye)

Location

Related Publications (2)

• Sofuoglu C, Fujita RA, Keskin K, Kamis O, Akcay N. Acute electrical muscle stimulation effects on strength and anaerobic power in soccer players. Int J Sports Med. 2025 Jun;46(7):501-509. doi: 10.1055/a-2563-9289. Epub 2025 Mar 20.

  PMID: 40112871 RESULT

• Keskin K, Akcay N, Ozmen T, Contarli N, Yildiz KC, Sofuoglu C, Kamis O, Rolnick N, de Queiros VS, Montoye A. Effects of different pre-exercise strategies on jumping performance in female volleyball players. J Sports Med Phys Fitness. 2025 Jan;65(1):59-68. doi: 10.23736/S0022-4707.24.16196-8. Epub 2024 Oct 3.

  PMID: 39360986 RESULT

MeSH Terms

Interventions

Isometric Contraction

Intervention Hierarchy (Ancestors)

Muscle Contraction; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena

Study Officials

• Neslihan Akçay, Doctorate

  Karabuk University

  STUDY CHAIR

Central Study Contacts

Neslihan Akçay, Doctorate

CONTACT

+905468426671; neslihanozcan@karabuk.edu.tr

Neslihan Akçay, Doctorate

CONTACT

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Masking Details: Triple (Participant, Care Provider, Outcomes Assessor) Participants were strictly separated and think their intervention is the main intervention. The same is true for care providers. Outcome assessors were unaware of participant group status and were not allowed to ask correspondingly
• Purpose: TREATMENT
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assoc. Prof. Dr.

Study Record Dates

• First Submitted: July 6, 2026
• First Posted: July 10, 2026
• Study Start: August 1, 2026
• Primary Completion (Estimated): August 30, 2026
• Study Completion (Estimated): September 5, 2026
• Last Updated: July 10, 2026

Record last verified: 2026-07

Locations

TU (1)