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Completed

NCT Number: NCT06603532

Effect of LL-BFRE Training on Volitional Muscle Activation in Subjects with Knee Joint Impairment

The aim of this study was to investigate whether 4 weeks of exercise training against low mechanical resistance in combination with partial blood flow restriction has an additional therapeutic effect on the patients' ability to activate the knee extensor muscle. Patients with chronic deficits in muscle strength due to knee injuries or surgery on one leg were invited to participate in this study on a completely voluntary basis.

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Key information

Conditions

Arthrogenic Muscle Inhibition Knee Injuries Knee Surgery Leg Injuries Wounds and Injuries

Age range

18 year–55 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Primorska, Faculty of Health Sciences, Izola, Slovenia

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About this study

The effects of low-load exercise with blood flow restriction (BFR) on the ability to voluntarily activate skeletal muscle in people with joint injuries are poorly understood. The aim of our study was to investigate the effects of low-load BFR training on the level of voluntary activation (AL) of the quadriceps femoris muscle assessed using the interpolated twitch technique in people with different knee joint injuries. Thirty-three orthopedic patients assigned to either the BFR group or the SHAM-BFR group participated in the study. Over a period of four weeks, the participants completed 12 training sessions of unilateral knee extension and leg press at 30 RM. The BFR group trained with a pneumatic cuff-induced blood flow restriction (pressure = 120-140 mmHg), while the SHAM-BFR group trained with a sham blood flow restriction (pressure = 20 mmHg) that did not interfere with normal muscle perfusion. The assessment of knee muscle capacity and function consisted of dynamometric measurements of maximal isometric strength and endurance of the knee extensor muscles, level of voluntary muscle activation, surface electromiography, pain intensity and assessment of perceived exertion. All tests and measurements were performed twice, once before the intervention (baseline) and once at the end of the 4-week training period (POST).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • no systemic illness,
  • no history of injuries to the contralateral knee,
  • pain intensity during exercise ≤ 2 on numeric pain rating scale (0-10).

Exclusion criteria

  • neuromuscular impairments,
  • spine or other lower limb injuries,
  • presence or history of any vascular diseases or deep vein thrombosis
  • pain intensity during exercise ≥ 3 on numeric pain rating scale (0-10).

Treatment and study plan

low-load blood flow restriction (BFR) training

Other

The training program lasted four weeks with three training sessions per week, for a total of 12 training sessions. Participants in the BFR group exercised with blood flow restriction caused by an inflatable cuff placed on the proximal part of the thigh and inflated to 120-140 mmHg. Subjects trained against the maximum mechanical resistance they could overcome thirty times (30 repetitions maximum; 30 RM). All training sessions were performed under the supervision of a physiotherapist and included leg press and knee extension exercises.

low-load resistance training

Other

The training program lasted four weeks with three training sessions per week, for a total of 12 training sessions. Participants in SHAM-BFR group performed an identical exercise protocol as experimental (BFR) group, while having thigh cuff inflated to only 20 mmHg, which did not affect normal muscle blood flow. Subjects trained against the maximum mechanical resistance they could overcome thirty times (30 repetitions maximum; 30 RM). All training sessions were performed under the supervision of a physiotherapist and included leg press and knee extension exercises.

Primary outcomes

  1. Quadriceps muscle isometric strength

    Time frame: Baseline and 4 weeks (post intervention)

    The measurement of the torque of the maximum volitional isometric contraction (MVIC) of the quadriceps femoris (QF) was performed on an isometric knee joint dynamometer. The test subject was seated, the hip joint was flexed to 85° and the lever arm was locked at 60° knee flexion. After warming up, the subject was instructed to perform the MVIC for 3-5 seconds with arms crossed over the chest, with no upper body movements allowed. Three consecutive MVICs were performed with each leg, separated by a 30-second rest period. The experimenter gave the subjects strong verbal encouragement during the tests. The highest average 1-second torque (Nm) of the three trials was considered relevant and used for further analysis.

  2. Maximal voluntary activation level of quadriceps muscle

    Time frame: Baseline and 4 weeks (post intervention)

    The degree of QF maximal voluntary activation (VAmax) was calculated as the ratio between the highest interpolated twitch contraction torque achieved during MVIC and the highest muscle twitch torque at rest measured during the first 10-second recovery period of after MVIC. The value is expressed as a percentage (%).

  3. Quadriceps muscle isometric endurance

    Time frame: Baseline and 4 weeks (post intervention)

    The test of QF isometric endurance was performed on an isometric knee joint dynamometer. The test subject was seated with the hip joint flexed to 85° and the lever arm locked at 60° knee flexion. After warming up, the test subject was instructed to attain 60% MVIC torque displayed on a computer screen and to maintain this until voluntary failure. The experimenter gave the subjects strong verbal encouragement during the test. QF muscle endurance was measured in seconds (s).

  4. Voluntary activation level of quadriceps muscle during isometric endurance test

    Time frame: Baseline and 4 weeks (post intervention)

    The degree of QF voluntary activation was evaluated in 10-s intervals during the isometric endurance test (VAendur). It was calculated as the ratio between the twitch torque attained in a given time interval and the highest muscle twitch torque at rest measured during the 20-second recovery period after the test. The value was expressed as a percentage (%).

  5. Surface EMG amplitude of quadriceps muscle during isometric endurance test

    Time frame: Baseline and 4 weeks (post intervention)

    The change in activation of v. medialis, v. lateralis and rectus f. muscles was measured using surface EMG during the isometric endurance test. The electrodes were positioned according to the SENIAM standards (Hermens et al., 2000) to avoid overlapping of the innervation zones and cross-talk between the muscles. EMG activity was amplified using a four-channel monitoring device with a sampling rate of 1000 Hz, an input impedance of 2MΏ and a bandwidth of 1-500 Hz. Smoothing the root mean square (RMS) of the filtered signal with a time window of 3000 ms was used to quantify the EMG amplitude (mV). The RMS EMG during the endurance test was expressed as percentage of the highest value attained during MVIC (% RMS EMG max).

Secondary outcomes

  1. knee and muscle pain

    Time frame: during each training session, 3-times per week, for 4 weeks

    The intensity of pain at rest and at the end of each exercise repetition was rated using a numerical pain scale (NPRS) from 0-10, with 0 is the absence of pain and 10 is the worst pain imaginable.

  2. ratings of perceived exertion

    Time frame: during each training session, 3-times per week, for 4 weeks

    Ratings of perceived exertion (RPE) were assessed at the end of each exercise set using the Borg 10 category-ratio scale, with 0 is no effort and 10 is an extreme physical effort.

Sponsors and collaborators

Lead sponsor

University of Ljubljana

Other

Collaborators

  • University Medical Centre Ljubljana
  • University of Primorska

Registry information

Official study title

Effect of Low-Load Blood Flow Restricted Training on Volitional Activation of Knee Extensor Muscles in Subjects with Knee Joint Impairment

Important dates

Study start
2019
Primary completion
2020
Study completion
2020
First posted
Sep 19, 2024
Registry last updated
Oct 3, 2024

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

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This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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