Training specificity performing single-joint vs. multi-joint resistance exercises among physically active females: A randomized controlled trial

Abstract

Resistance-training of the lower limbs can be performed using exercises moving one (single-joint exercises) or several joints (multi-joint exercises). This study compared the effects of training one multi-joint exercise (leg press) or two single-joint exercises (leg extension and kickback) on dynamic and isometric strength and the transferability of dynamic strength between exercises. Fifty-three physically active women were randomized to a multi-joint (MJ) training group (age = 21.95±0.82 years, mass = 64.85±5.76 kg, height = 167.35±2.47 cm; n = 20), single-joint (SJ) training group (age = 22.56±1.66 years, mass = 64.85±5.76 kg, height = 165.94±2.84 cm; n = 18), or a control (CON) group (age = 21.27±0.68 years, mass = 68.43±4.86 kg, height = 168.63±2.84 cm; n = 15). The training groups participated in an 8-week supervised single- or multi-joint lower limb training consisting of 18 sessions. Pre- and post-training, six repetitions maximum (RM) and maximal voluntary isometric contraction in the three exercises were assessed, along with electromyography of the superficial quadriceps muscles. Improvements in all dynamic exercises were greatest after training the specific exercises (ES = 1.26-2.14, P<0.001-0.025) and all were greater in the training groups than in the CON group (ES = 1.43-3.31, P<0.001-0.021). The SJ group improved 6RM in leg extension and kickback more than leg press (ES = 1.51 and 2.04, respectively, P<0.001), whereas the MJ group improved leg press 6RM more than kickback (ES = 1.10, P = 0.002). However, leg press and leg extension strength improved similarly in the MJ group (ES = 0.54, P = 0.072). All strength and electromyographic measures remained unchanged in the CON group (ES = 0.00-0.44, P = 0.412-0.966). Improved dynamic strength in leg press, kickback and leg extension is best attained by training the specific exercises, but both training modalities can improve strength across all exercises.

Fig 1

Starting position for the a) leg press, b) leg extension, and c) kickback.

Fig 2

Absolute change (kg) in 6RM strength from pre- to post-test for the control (white bar), SJ (gray bar) and MJ groups (black bar). Error bars represent 95% confidence interval. * = Significant change from pre- to post-test (P < 0.001). † = Significantly lower change than the training groups (P < 0.01). # = Significant difference between training groups (P < 0.01). ** = Significant difference between exercises (P < 0.01).

Fig 3

Accumulated volume (kg) throughout the training period for the SJ (grey line) and MJ group (black line). Error bars represent 95% confidence interval.