Joint Loading in the Lower Extremities During Elliptical Exercise

Tung-Wu Lu; Hui-Lien Chien; Hao-Ling Chen

Disclosures

Med Sci Sports Exerc. 2007;39(9):1651-1658. 

In This Article

Results

The mean step length and cadence were 52.17 cm (SD = 3.55) and 105.76 steps per minute (SD = 9.53) during level walking, and those for EE were 50.56 cm (SD = 2.14), and 52.20 rpm (SD = 2.34), or 104.40 steps per minute, respectively. There was no significant difference between these two activities (step length, P = 0.130; cadence, P = 0.616).

The pedal moved along an oblique ellipse with a major axis of 50.56 ± 2.14 cm in length and tilted 6.19 ± 0.36° anteriorly (downward slope), and a minor axis of 17.23 ± 1.19 cm, while keeping the mediolateral center-to-center distance between the two pedals at about 25 cm. With the movement ranges, the subjects managed to keep the motion of the COM within 1.7 cm anteroposteriorly, 5.1 cm vertically, and 6.0 cm mediolaterally during a complete cycle. Corresponding values for level walking were 111.0, 2.9, and 4.7 cm, respectively.

The patterns of the anteroposterior component of the GRF during walking and PRF during EE were similar, but those for the other two components were different (Figure 2). The GRF was present only during the stance phase, whereas the PRF existed for the entire cycle of EE. During level walking the vertical and mediolateral reaction forces had double peaks, whereas only single peaks were observed during EE. Compared with walking, the PRF was positioned and directed more posteriorly and medially in the stance phase. In early stance, the magnitude of the vertical PRF of EE was smaller (EE: 94.44 ± 9.00% BW, walking: 103.05 ± 5.12% BW, P = 0.003), whereas the medial (EE: 8.09 ± 2.08% BW, walking: 4.36 ± 2.00% BW, P < 0.0001) and posterior (EE: 15.83 ± 3.13% BW; walking: 13.61 ± 2.09% BW, P = 0.03) shear forces were greater. The maximum loading rates of the vertical, mediolateral, and anteroposterior components during EE were 3.78 ± 1.75, 0.42 ± 0.16, and 0.85 ± 0.50 BW.s-1, respectively. The corresponding values for level walking were 48.78 ± 16.98, 4.61 ± 2.07, and 6.27 ± 3.03 BW.s-1. The maximum loading rates during EE were all significantly smaller than the corresponding values during walking (all components, P < 0.0001). Stick figures of a typical subject with the measured PRF/GRF vectors superimposed are shown in Figure 3.

Figure 2.

Ensemble-averaged PRF (solid lines) during elliptical exercise and GRF (dashed lines) during level walking. *Significant difference between the two activities (P < 0.05).

Figure 3.

Stick figures of the pelvis-leg apparatus of a typical subject with the PRF and GRF vectors at instances of (A) heelstrike, (B) peak knee extensor moment, and (C) peak anterior shear force during EE and level walking. The dynamic GRF and PRF vectors are shown as filled arrows, and open arrows with magnitudes equal to the body weight are superimposed along each GRF/PRF vector for reference. Joint centers are shown as filled circles, and bony landmarks for drawing the stick figures are shown as open circles.

In the sagittal plane, the two activities showed similar angular patterns for the hip and knee, but with different amplitudes (Figure 4). The hip and knee remained more flexed for almost the entire EE cycle. The differences for the ankle joint occurred in the second half of the movement cycle, mainly during swing (Figure 4). Compared with walking, EE had significantly greater peak flexion angles at the hip, knee, and ankle ( Table 1 ). In the frontal plane, the hip joint remained slightly abducted during most of the EE cycle, whereas it was adducted during the stance phase of gait (Figure 4). The knee had similar motion patterns during the two activities, but it had significantly greater peak abduction angles during EE ( Table 1 ). The ankle remained adducted during the late stance phase and early swing phase of EE. The angular motions of the ankle joint were different between the two activities, both in pattern and magnitude. In the transverse plane, the ankle joint remained internally rotated throughout almost the entire EE cycle, and the peak internal rotation angles were significantly greater during EE ( Table 1 ).

Figure 4.

Ensemble-averaged three-dimensional joint angles at the (A) hip, (B) knee, and (C) ankle joints during elliptical exercise (solid lines) and level walking (dashed lines). *Significant difference between the two activities (P < 0.05).

In the sagittal plane, the patterns of the hip moments during EE were quite different from those during walking (Figure 5). Flexor moments were required at the hip throughout almost the whole EE cycle. During stance, peak hip flexor moments during EE were significantly greater than those during walking, whereas peak hip extensor moments were smaller (P = 0.003) ( Table 2 ). Similar patterns of the sagittal knee moments were found during the two activities, but extensor moments were needed throughout the EE cycle, and flexor moments were needed during walking (Figure 5). Both peak knee extensor moments during EE were significantly greater than those during level walking ( Table 2 ). The ankle required much smaller plantarflexor moments during the EE cycle than during level walking ( Table 2 ).

Figure 5.

Ensemble-averaged three-dimensional joint moments at the (A) hip, (B) knee, and (C) ankle during elliptical exercise (solid lines) and level walking (dashed lines). *Significant difference between the two activities (P < 0.05).

In the frontal and transverse planes, the M patterns and magnitudes of the moment components were largely different between EE and walking (Figure 5). During stance phase, all peak abductor moments during EE were significantly smaller than those during level walking ( Table 2 ). Peak knee internal rotation moments and ankle external rotation moments were also smaller during EE ( Table 2 ).

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