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

Effect of Low-Load Blood Flow Restricted Training on Volitional Activation of Knee Extensor Muscles 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.

Study Overview

• Status: Completed
• Conditions: Knee Injuries; Knee Surgery; Arthrogenic Muscle Inhibition
• Intervention / Treatment: Other: low-load blood flow restriction (BFR) training; Other: low-load resistance training

Detailed Description

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).

• Study Type: Interventional
• Enrollment (Actual): 36
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Slovenia
  • Izola, Slovenia, 6310
    • University of Primorska, Faculty of Health Sciences
  • Ljubljana, Slovenia, 1000
    • University of Ljubljana, Faculty of Health Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

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).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: low-load blood flow restriction (BFR) resistance training; Group of patients that performed the experimental exercise training against low mechanical resistance (workload) with blood flow restriction (BFR) in the active thigh muscles.	Other: low-load blood flow restriction (BFR) training; 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.
Sham Comparator: low-load resistance training; Group of patients that performed exercise training against low mechanical resistance (workload) with sham blood flow restriction (SHAM-BFR) in the active thigh muscles.	Other: low-load resistance training; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Quadriceps muscle isometric strength	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.	Baseline and 4 weeks (post intervention)
Maximal voluntary activation level of quadriceps muscle	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 (%).	Baseline and 4 weeks (post intervention)
Quadriceps muscle isometric endurance	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).	Baseline and 4 weeks (post intervention)
Voluntary activation level of quadriceps muscle during isometric endurance test	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 (%).	Baseline and 4 weeks (post intervention)
Surface EMG amplitude of quadriceps muscle during isometric endurance test	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).	Baseline and 4 weeks (post intervention)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
knee and muscle pain	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.	during each training session, 3-times per week, for 4 weeks
ratings of perceived exertion	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.	during each training session, 3-times per week, for 4 weeks

Collaborators and Investigators

• Sponsor: University of Ljubljana
• Collaborators: University of Primorska; University Medical Centre Ljubljana
• Investigators: Principal Investigator: Alan Kacin, PhD, PT, Prof, University of Ljubljana, Faculty of Health Studies

Study record dates

Study Major Dates

• Study Start (Actual): April 16, 2019
• Primary Completion (Actual): March 20, 2020
• Study Completion (Actual): September 9, 2020

Study Registration Dates

• First Submitted: September 6, 2024
• First Submitted That Met QC Criteria: September 16, 2024
• First Posted (Actual): September 19, 2024

Study Record Updates

• Last Update Posted (Actual): October 3, 2024
• Last Update Submitted That Met QC Criteria: October 1, 2024
• Last Verified: September 1, 2024

More Information

Terms related to this study

• Keywords: controlled clinical trial; knee injury; arthrogenic muscle inhibition; level of volunaty muscle activation; blood flow restriction resistance exercise
• Additional Relevant MeSH Terms: Wounds and Injuries; Leg Injuries; Knee Injuries
• Other Study ID Numbers: 0120-496-2018-8; P3-0043 (Other Grant/Funding Number: Slovenian Research and Innovation Agency); 20190041; 20200063 (Other Grant/Funding Number: University Clinical Center Ljubljana)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All collected IPD in anonymized form.
• IPD Sharing Time Frame: No limit.
• IPD Sharing Access Criteria: All IPD will be shared upon reasoned request for the purpose of further scientific analysis (i.e. systematic reviews, meta-analyzes, etc.). A proposal describing the planned analyzes must be submitted in writing to the principal investigator, Dr. Alan Kacin, by email to alan.kacin@zf.uni-lj.si.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No