EMG Activity With Use of a Hands-Free Single Crutch vs a Knee Scooter

Abstract

Background: Foot and ankle injuries frequently require a period of nonweightbearing, resulting in muscle atrophy. Our previous study compared a hands-free single crutch (HFSC) to standard axillary crutches and found increased muscle recruitment and intensity while using the HFSC. Knee scooters are another commonly prescribed nonweightbearing device. The purpose of this study is to examine the electromyographic (EMG) differences between an HFSC and knee scooter, in conjunction with device preference and perceived exertion.

Methods: A randomized crossover study was performed using 30 noninjured young adults. Wireless surface EMG electrodes were placed on the belly of the rectus femoris (RF), vastus lateralis (VL), lateral gastrocnemius (LG), and gluteus maximus (GM). Participants then ambulated along a 20-m walking area while 15 seconds of the gait cycle was recorded across 3 conditions: walking with a knee scooter, an HFSC, and with no assistive device. Mean muscle activity and peak EMG activity were recorded for each ambulatory modality. Immediately following testing, patient exertion and device preference was recorded.

Results: The RF, LG, and GM showed increased peak EMG activity percentage, and the LG showed increased mean muscle activity while using the HFSC compared with the knee scooter. When comparing the knee scooter and HFSC to walking, both showed increased muscle activity in the RF, VL, and LG but no difference in the GM. There was no statistical difference in participant preference, whereas the HFSC had a statistically significant higher perceived exertion than the knee scooter (P < .001).

Conclusion: In this group of young, healthy noninjured volunteers, the HFSC demonstrated increased peak EMG activity in most muscle groups tested compared with the knee scooter.

Level of evidence: Level II, prospective comparative study.

Keywords: ambulatory aid; assistive device; electromyography; hands-free single crutch; iWALKFree; knee scooter; lower extremity injury; nonweightbearing.

Figure 1.

Trigno Avanti wireless Bluetooth sensors placement on a participant wearing the hands-free single crutch (iWALKFree). The left sensor is attached to the skin overlying the belly of the lateral gastrocnemius, the middle is over the belly of the vastus lateralis, and the right electrode is overlying the belly of the rectus femoris. The gluteus maximus sensor cannot be seen in this image.

Figure 2.

Participant using a knee scooter. The nonweightbearing leg is held in a horizontal position while the contralateral leg provides propulsion. One sensor can be seen attached to the skin overlying the rectus femoris.

Figure 3.

Hands-free single crutch (HFSC [iWALKFree]) and Trigno Avanti wireless Bluetooth sensors attached to the dominant leg of a participant. The HFSC holds the nonweightbearing leg in a horizontal position, allowing for bipedal gait with no loadbearing through the injured area. The sensors are attached to the skin overlying the lateral gastrocnemius (left), vastus lateralis (middle), and rectus femoris (right). The gluteus maximus sensor cannot be seen in this image.

Figure 4.

Example of the electromyography graphs recorded from the lateral gastrocnemius of 1 participant in the study. All graphs are set to the same scale. The top graph was recorded while using the hands-free single crutch (HFSC), the second while using the knee scooter, and the third while walking without an assistive device. The graphs show that the HFSC demonstrates increased muscle intensity when compared to the knee scooter and levels of cyclic contraction similar to walking.

Figure 5.

Side-by-side comparison of the mean RMS muscle activity in each muscle while using the 3 different ambulatory modalities (hands-free single crutch [HFSC], knee scooter, and walking without an assistive device). Statistical significance is marked with an asterisk.