Abstract
Low-intensity resistance exercise combined with blood flow restriction has been shown to elicit hormonal and neuromuscular responses similar to those with high-intensity resistance exercise. However, muscle fatigue characteristics during resistance exercise with restricted blood flow have not been clarified. Therefore, we measured maximal voluntary torque values during isokinetic concentric leg extensions across 30 repetitions at 180°/s either with blood flow restriction (BFR) or without restriction (CON) in eight healthy adults. The exercise was performed at the rate of either 30 repetitions/minute (BFR30 and CON30) or 15 repetitions/minute (BFR15 and CON15) designed to allow different rest intervals between contractions. Muscle fatigue was quantified by two methods: slope of peak isokinetic torque values through the 30th repetition and percent decrease in force from the first 5 repetitions to the last 5 repetitions. At the rate of 30 repetitions/minute, both fatigue rates were similar between BFR and control group. On the contrary, both fatigue rates were significantly higher in BFR15 group than the CON15 group (p<0.05). The results indicate that during resistance exercise performed with longer inter-repetition rest intervals, blood flow restriction is more effective at inducing muscle fatigue and thus may increase the training response. Furthermore, inter-repetition rest intervals of less than 3.5 seconds can increase fatigue level regardless of muscle perfusion.
