Muscle specific declines in oxygen saturation during acute ambulation with hands-free and conventional mobility devices.

Disuse is associated with reduced muscle oxygen saturation (SmO2). Improving oxygen delivery to tissues is important for healing, preventing muscle atrophy, and reducing the risk of deep vein thrombosis. Mobility devices are used during disuse periods to ambulate and protect the injured limb. This study examined SmO2 in walking and ambulation with various mobility devices. Thirty-eight participants randomly completed four, ten-minute trials which included: (1) walking, (2) medical kneeling scooter (MKS), (3) hands-free crutch (HFC), and (4) axillary crutch (AC). During each trial, near infrared spectroscopy sensors were placed on the vastus lateralis (VL), biceps femoris (BF), and lateral gastrocnemius (LG) of the right limb. Compared to walking, all mobility devices showed a decline in SmO2 in the VL of ∼10% (mean ± SD; 75% ± 12%-65% ± 17%, P < 0.05). In the BF, SmO2 declined ∼9% in AC compared to walking (76% ± 12%-67% ± 17%, P = 0.025). In the LG, SmO2 declined in AC (64% ± 16%) compared to MKS (70% ± 15%, P = 0.005). There were no differences in LG SmO2 compared to walking (69% ± 13%) in MKS (P > 0.05) or HFC (65% ± 15%, P > 0.05). In young, healthy volunteers, the use of mobility devices altered muscle oxygenation in several muscles. AC reduced muscle oxygenation in the VL, BF, and LG; while MKS and HFC maintained BF and LG muscle oxygenation at a level consistent with ambulatory walking.

Popliteal Blood Flow With Lower-Extremity Injury Mobility Devices.

Background: Ambulation devices may differ in their utility, muscle activation patterns, and how they affect regional blood flow. This study aimed to evaluate popliteal blood flow and vessel dimensions in response to ambulation with a hands-free crutch (HFC), axillary crutches (AC), a medical kneeling scooter (MKS), and regular walking in healthy adults. Methods: HFC, AC, MKS, and regular walking were completed in a random order by 40 adults aged 18-45 years. Participants ambulated at a comfortable pace for 10 minutes with each device. At baseline and immediately following each trial, a trained operator used diagnostic ultrasonography to capture popliteal vein and artery dimensional and flow characteristics. Results: Significant increases were observed from baseline (0.65 ± 0.23 cm) in venous diameter following walking (0.71 ± 0.21 cm, P = .012) and MKS (0.73 ± 0.21 cm, P = .003). Venous blood flow was also significantly different between conditions (P = .009) but was only greater following walking (124 ± 79 mL/min) compared to MKS (90 ± 64 mL/min, P = .021). No differences were observed in arterial dimensions between ambulation conditions. Significant increases were found in arterial blood flow from baseline (107 ± 69 mL/min) following walking (184 ± 97 mL/min, P < .001) and HFC (163 ± 86 mL/min, P < .001). Arterial blood flow following walking was greater than AC (132 ± 72 mL/min, P = .016) and MKS (128 ± 74 mL/min, P = .003). Conclusion: We found an average decrease in venous time-averaged mean velocity between walking and use of the MKS, but no such decrease with either HFCs or use of ACs in this healthy experimental cohort. Level of Evidence: Level III, diagnostic comparative study.

Energy Expenditure and Substrate Utilization with Hands-Free Crutches Compared to Conventional Lower-Extremity Injury Mobility Devices.

Background: A Hands-Free crutch (HFC) is a relatively new device that can be used during the nonweightbearing period to increase mobility. The primary aim of this investigation was to examine aerobic oxygen consumption (V.o2) and substrate utilization with HFC compared to conventional ambulation devices as well as normal ambulation. A secondary purpose was to quantify perceived exertion, pain, and performance during each ambulation condition. Methods: Forty participants completed 4 separate 10-minute ambulation conditions around a rectangular course. The order of the ambulation conditions was randomized and consisted of (1) walking, (2) medical knee scooter (MKS), (3) HFC, and (4) axillary crutch (AC). Indirect calorimetry was used to determine V.o2 and the respiratory exchange ratio (RER), an indicator of substrate utilization. Perceived exertion and pain were also assessed using questionnaires. Results: All mobility devices significantly elevated V.o2 (+35%) compared to walking (13.14 ± 1.70 mL/kg/min; P < .001). AC had significantly greater V.o2 requirements (20.26 ± 2.62 mL/kg/min) compared to both the MKS (15.28 ± 2.29 mL/kg/min; P < .001) and HFC (15.88 ± 2.03 mL/kg/min; P < .001). There was no difference in average V.o2 between MKS and HFC (P = .368). Compared to walking (0.78 ± 0.43), RER was significantly elevated in MKS (0.81 ± 0.05, P < .001) and AC (0.84 ± 0.06, P < .001), but not in HFC (0.79 ± 0.04, P = .350). RPE and pain were elevated in all ambulatory conditions (all P values <.001). Pain was significantly greater in AC compared with MKS (P < .001) and HFC (P < .001). Conclusion: HFC and MKS share similar V.o2 requirements over a 10-minute ambulation interval and are below those needed in AC. Substrate utilization in HFC was similar to regular walking with a greater reliance on lipid utilization for energy as evidenced by a lower RER. Exertion and pain scores were the most tolerable in HFC and MKS. Level of Evidence: Level II, prospective comparative study.