Squatting exercises in older adults: kinematic and kinetic comparisons

Abstract

Purposes: Squatting activities may be used, within exercise programs, to preserve physical function in older adults. This study characterized the lower-extremity peak joint angles, peak moments, powers, work, impulse, and muscle recruitment patterns (electromyographic; EMG) associated with two types of squatting activities in elders.

Methods: Twenty-two healthy, older adults (ages 70-85) performed three trials each of: 1) a squat to a self-selected depth (normal squat; SQ) and 2) a squat onto a chair with a standardized height of 43.8 cm (chair squat; CSQ). Descending and ascending phase joint kinematics and kinetics were obtained using a motion analysis system and inverse dynamics techniques. Results were averaged across the three trials. A 2 x 2 (activity x phase) ANOVA with repeated measures was used to examine the biomechanical differences among the two activities and phases. EMG temporal characteristics were qualitatively examined.

Results: CSQ generated greater hip flexion angles, peak moments, power, and work, whereas SQ generated greater knee and ankle flexion angles, peak moments, power, and work. SQ generated a greater knee extensor impulse, a greater plantar flexor impulse and a greater total support impulse. The EMG temporal patterns were consistent with the kinetic data.

Conclusions: The results suggest that, with older adults, CSQ places greater demand on the hip extensors, whereas SQ places greater demand on the knee extensors and ankle plantar flexors. Clinicians may use these discriminate findings to more effectively target specific lower-extremity muscle groups when prescribing exercise for older adults.

FIGURE 1

Free-body diagram illustrating the internal (muscular) moments (M) and joint angles (θ) for the ankle, knee, and hip. Directional arrows represent positive joint moments for hip extension, knee extension, and ankle plantar flexion. Joint angles are measured in degrees with increasing joint angles representing greater hip flexion, knee flexion, and ankle dorsiflexion.

FIGURE 2

The squat exercise, performed while the participant is instrumented for biomechanical analysis.

FIGURE 3

The chair squat exercise, performed while the participant is instrumented for biomechanical analysis.

FIGURE 4

Ensemble average kinetic and EMG records for the hip during the squat SQ (left side) and chair squat CSQ (right side) normalized to 100% of the movement cycle. A, hip flexion angle in degrees; B, sagittal plane moments in N·m·kg⁻¹; C, power in W·kg⁻¹; D, EMG activity of the lower gluteus maximus normalized to maximum activity during the squat; E, EMG activity of the hamstrings muscle group normalized to maximum activity during the squat. Vertical labels represent the initiation and termination of chair contact during CSQ.

FIGURE 5

Ensemble average kinetic and EMG records for the knee during the squat SQ (left side) and chair squat CSQ (right side) normalized to 100% of the movement cycle. A, knee flexion angles in degrees; B, sagittal plane moments in N·m·kg⁻¹; C, power in W·kg⁻¹; D, EMG activity of the vastus lateralis muscle normalized to maximum activity during the squat. Vertical labels represent the initiation and termination of chair contact during CSQ.

FIGURE 6

Ensemble average kinetic and EMG records for the ankle during the squat SQ (left side) and chair squat CSQ (right side) normalized to 100% of the movement cycle. A, ankle dorsiflexion angles in degrees; B, sagittal plane moments in N·m·kg⁻¹; C, power in W·kg⁻¹; D, EMG activity of the gastrocnemius muscle normalized to maximum activity during the squat. Vertical labels represent the initiation and termination of chair contact during CSQ.

FIGURE 7

Peak hip flexion, knee flexion, and ankle dorsiflexion angles in degrees. Values are mean ± SD. *Denotes a statistically significant difference between the squat and chair squat.

FIGURE 8

Total extensor work (J·kg⁻¹) generated at the hip, knee, and ankle during the squatting activities. Values are mean ± SD. *Denotes a statistically significant difference between the squat and chair squat.