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Matthew K. Seeley, Ryan P. Sandberg, Joshua F. Chacon, Merrill D. Funk, Neil Nokes and Gary W. Mack

Context:

Individuals using traditional axillary crutches to ambulate expend approximately twice as much energy as individuals who perform able-bodied gait. A relatively novel spring-loaded crutch now being marketed may reduce metabolic energy expenditure during crutch ambulation. This idea, however, had not yet been tested.

Objective:

To determine whether the novel spring-loaded crutch reduces oxygen consumption during crutch ambulation, relative to traditional-crutch ambulation. A secondary purpose was to evaluate the design for subject-perceived comfort and ease of use.

Design:

Within-subject.

Setting:

Indoor track.

Participants:

10 able-bodied men and 10 able-bodied women.

Interventions:

The independent variable was crutch design. Each subject ambulated using 3 different crutch designs (traditional, spring-loaded, and modified spring-loaded), in a randomized order.

Main Outcome Measures:

The primary dependent variable was oxygen consumption. Secondary dependent variables were subject-perceived comfort and ease of use, as rated by the subjects using a 100-mm visual analog scale. Dependent variables were compared among the 3 crutch designs using a 1-way repeated-measures ANOVA (α = .05).

Results:

Oxygen consumption during spring-loaded-crutch ambulation (17.88 ± 2.13 mL · kg−1 · min−1) was 6.2% greater (P = .015; effect size [ES] = .50) than during traditional axillary-crutch ambulation (16.84 ± 2.08 mL · kg−1 · min−1). There was no statistically significant difference (P = .068; ES = −.45) for oxygen consumption between spring-loaded-crutch ambulation and ambulation using the modified crutch (17.03 ± 1.61 mL · kg−1 · min−1). Subjects perceived the spring-loaded crutch to be more comfortable (P < .001; ES = .56) than the traditional crutch. There was no difference (P = .159; ES = −.09) between the spring-loaded and traditional crutches for subject-perceived ease of use.

Conclusions:

Compared with traditional axillary crutches, the novel spring-loaded crutch may be more comfortable but does not appear to benefit subjects via reduced metabolic energy expenditure.

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Merrill D. Funk, Cindy L. Salazar, Miriam Martinez, Jesus Gonzalez, Perla Leyva, David Bassett Jr. and Murat Karabulut

Fifty-two participants walked on a treadmill at 4.8 km/h for 500 steps while wearing four Samsung Galaxy S4 smartphones on the arm, waist, pocket, and hand while each phone simultaneously ran five popular smartphone apps. Actual steps were measured using a hand tally device. Steps were recorded from each smartphone app and compared to the tally counter using repeated measures analysis of variance (ANOVA) tests, and equivalence testing. Of the 20 step measurements recorded (five apps at four locations), all but four (Accupedo at the arm, waist, and pocket; S-Health at the pocket) produced mean underestimations of step counts. ANOVAs showed significant differences between the phone at the hand location for all apps compared to the tally counter (p < .05); three apps had differences at the waist (p < .01), Runtastic had differences at the arm (p < .001), and no differences occurred between the pocket location and the hand tally counter for any of the apps (p > .05). The 90% confidence interval for all apps, except for G-Fit, fell within the equivalence zone for the phone in the pocket while the phone at the hand location included only S-Health within the equivalence zone. Using a Samsung Galaxy S4 smartphone to measure steps at a 4.8 km/h walking pace while carrying the phone in the hand may produce significant errors. However, using the S-Health app while carrying a phone in the pocket appears to provide the most accurate step count in a controlled environment.