Ankle Position During Leg Curls
How does it affect hamstring muscle activation?
Researchers from Londrina State University in Brazil set out to answer the following: Does where you position your ankle during a seated leg curl actually change which muscles are engaged and how hard they work? Using ultrasound imaging to quantify real muscle swelling after exercise, they tested 17 untrained young women performing seated leg curls in two conditions: with the ankle in a neutral position (foot at 90 degrees to the shin) and with the ankle in plantar flexion (approximately 30 degrees). The results reveal a clear hierarchy of muscle engagement depending on ankle position, with implications for lifters looking to target specific muscle groups.
Aim
The study examined whether ankle position during seated leg curls influences muscle engagement in the hamstrings and calf muscles (both the lateral and medial gastrocnemius). Researchers used ultrasound to measure muscle swelling as a marker of muscle engagement because swelling directly reflects the metabolic demand and blood flow response to muscle contraction. The secondary aim was to compare loads and training volume between the two ankle positions.
Methods
Seventeen untrained women (average age 24.5 years) participated in a carefully controlled crossover design. Each participant performed three separate test sessions, one week apart:
Seated leg curls with neutral ankle position
Seated leg curls with plantar flexion (ankle pointed down)
A control session where they simply rested without exercising
Before the experimental sessions, participants completed a 12-repetition maximum (12RM) strength test in both ankle positions to establish their training load. On test days, they performed a warm-up set at 50% of their 12RM load with 12 repetitions, followed by three sets taken to muscle failure using their full 12RM weight, with 2 minutes of rest between sets.
Ultrasound measurements of muscle thickness were taken on the right leg immediately before exercise and immediately after (within about 1 minute of finishing). Measurements captured the hamstrings at 50% of the distance between hip and knee, the lateral calf at one-third distance between knee and ankle, and the medial calf at the point of maximum circumference. The measurement reliability was confirmed to be high, with intraclass correlations (ICC) of 0.83 for hamstrings and 0.92 for both calf muscles.
Results
Lateral Calf (Lateral Gastrocnemius): Only the neutral ankle position produced meaningful muscle swelling in this muscle. The neutral position caused 0.07 cm of swelling compared to the control condition, and 0.07 cm more swelling than the plantar flexion position. The plantar flexion position produced essentially no additional swelling compared to the control (0.01 cm difference).
