<bold>Purpose.</bold> Single joint (open kinetic chain) and multiple joint (closed kinetic chain) exercises have been recommended in rehabilitation of patients with anterior knee pain. Single joint exercises are common exercises to strengthen selected muscle groups. The advantage of single joint exercises is a low risk of pain due to their limited technical complexity. Multiple joint exercises are more demanding from the standpoint of human motor performance. The efficiency of power training after single and multiple joint exercises was the aim of the study. <bold>Basic procedures.</bold> Forty eight men constituted the study sample (aged 22 ± 0.8 years, body weight - 78.3 ± 6.4 kg, body height 183 ± 5.6 cm). They were informed about the experimental procedure as well as the purpose of the study, and gave their consent to take part in the experiment. That study was approved by the local research ethics committee. After control measurements the participants were randomized into four groups (n = 12 each): two groups performing multiple joint exercises (A - jumps on an inclined plane, B - vertical jumps), and two single joint exercises (C - knee extensions with linear resistance load - elastic loads, D - knee extensions with inertial loads). The exercises were carried out in four-week exercise sessions, for five days a week. 4 sets of 10 reps (jumps or extensions) with 120-second intervals were applied during each session. The counter movement jump power (on a Kistler force plate with BioWare 4.0 software), during isokinetic knee motion at 240, 180, 60 and 30 deg/s (Biodex Medical System 3 Pro) and EMG (Mega Electronics System) of the Rectus Femoris and Vastus Lateralis muscles were recorded seven times (once before, three times during and three times after training). <bold>Main findings.</bold> The external load for single and multiple joint exercises was adjusted by individual power of motion. However the training volume (external work) was lowered twice during training with single joint exercises. Muscle force during isokinetic tests was significantly correlated with velocity achieved during training. Therefore the homogeneity of the movement structure between training and control exercises is required. <bold>Conclusions.</bold> Velocity of motion during exercise and time of muscle work are the most important factors determining efficiency of single- and multiple-joint exercises.
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