Comparing the Effects of Push and Hold Isometric Training on Strength and Musculotendinous Adaptations: A Within-Subject Randomized Controlled Trial.

Both PIMA and HIMA training increased isometric torque, but only PIMA improved concentric and eccentric torque.

• Increased isometric torque was found following both conditions (p < 0.05, g = 0.30–0.36)
• Concentric torque only increased following PIMA (p < 0.05, g = 0.31)
• Eccentric torque only increased following PIMA (p < 0.01, g = 0.50)
• The study used a within-subject randomized controlled trial design with 20 limbs across 10 adults

Both PIMA and HIMA training increased quadriceps muscle thickness and vastus lateralis fascicle length.

• Both conditions increased muscle thickness (p < 0.05, g = 0.27–0.88)
• Both conditions increased vastus lateralis fascicle length (p < 0.05, g = 0.20–0.31)
• Assessments were performed via ultrasound before and after the 6-week intervention
• Training involved 4–6 repetitions of 20-second contractions at 70% of maximal voluntary contraction at an 80° knee angle

HIMA produced greater increases in total quadriceps and rectus femoris muscle thickness compared to PIMA.

• The increase in total quadriceps thickness was greater in HIMA (p < 0.05, g = 0.46)
• The increase in rectus femoris thickness was especially greater in HIMA (p < 0.05, g = 1.44), representing a large effect size
• HIMA required the limb to maintain a set joint angle while resisting an isotonic lever
• PIMA required subjects to exert force against a fixed lever

Only HIMA training increased patellar tendon thickness.

• Only HIMA increased patellar tendon thickness (p < 0.05, g = 0.12)
• The effect size for patellar tendon thickness change was small (g = 0.12)
• Patellar tendon thickness was assessed via ultrasound pre- and post-intervention
• PIMA did not produce a significant change in patellar tendon thickness

The study design used a within-subject randomized controlled trial with each limb randomly assigned to either PIMA or HIMA conditions.

• Twenty limbs across 10 adults (5 men, 5 women, age: 31.4 ± 6.5 years) were randomly assigned to PIMA or HIMA conditions
• Subjects underwent 12 training sessions over 6 weeks
• Subjects completed isometric, concentric, and eccentric knee extension assessments for both limbs before and after the intervention
• Contractions were performed at 70% of maximal voluntary contraction for 20 seconds at an 80° knee angle, for 4–6 repetitions

The authors concluded that larger sample sizes and more ecologically valid training programs are needed to further differentiate between PIMA and HIMA isometric training types.

• The current study included only 10 participants (20 limbs), which the authors acknowledge as a limitation
• The authors call for 'larger sample sizes and more ecologically valid training programs' to elucidate potential differences
• Despite recent interest in delineating PIMA and HIMA, training-induced adaptations had not previously been examined
• The within-subject design was used to control for individual variability between participants