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.

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).

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).