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Matthew K. Seeley, Iain Hunter, Thomas Bateman, Adam Roggia, Brad J. Larson and David O. Draper

Context:

A novel spring-loaded-crutch design may provide patients additional forward velocity, relative to traditional axillary crutches; however, this idea has not yet been evaluated.

Objective:

To quantify elastic potential energy stored by spring-loaded crutches during crutch–ground contact and determine whether this energy increases forward velocity for patients during crutch ambulation. Because elastic potential energy is likely stored by the spring-loaded crutch during ambulation, the authors hypothesized that subjects would exhibit greater peak instantaneous forward velocity during crutch–ground contact and increased preferred ambulation speed during spring-loaded-crutch ambulation, relative to traditional-crutch ambulation.

Design:

Within-subject.

Setting:

Biomechanics laboratory.

Participants:

10 healthy men and 10 healthy women.

Interventions:

The independent variable was crutch type: Subjects used spring-loaded and traditional axillary crutches to ambulate at standardized and preferred speeds.

Main Outcome Measures:

The primary dependent variables were peak instantaneous forward velocity and preferred ambulation speed; these variables were quantified using high-speed videography and an optoelectronic timing device, respectively. Between-crutches differences for the dependent variables were evaluated using paired t tests (α = .05). Elastic potential energy stored by the spring-loaded crutches during crutch–ground contact was also quantified via videography.

Results:

Peak forward velocity during crutch–ground contact was 5% greater (P < .001) for spring-loaded-crutch ambulation than for traditional-crutch ambulation. Preferred ambulation speed, however, did not significantly differ (P = .538) between crutch types. The spring-loaded crutches stored an average of 2.50 ± 1.96 J of elastic potential energy during crutch–ground contact.

Conclusions:

The spring-loaded crutches appear to have provided subjects with additional peak instantaneous forward velocity. This increased velocity, however, was relatively small and did not increase preferred ambulation speed.

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Kazuto Sakita, Matthew K. Seeley, Joseph William Myrer and J. Ty Hopkins

Context:

Standing and side-lying external-rotation exercises produce high activation of the deltoid and infraspinatus. Slight shoulder abduction during these exercises may decrease deltoid activity and increase infraspinatus activity.

Objective:

To determine if the addition of a towel under the arm during standing and side-lying external rotation affects infraspinatus, middle and posterior deltoid, and pectoralis major activation characteristics compared with a no-towel condition.

Design:

Controlled laboratory study.

Participants:

20 male volunteers (age 26 ± 3 y, height 1.80 ± 0.07 m, mass 77 ± 10 kg) who were right-hand dominant and had bilaterally healthy shoulders with no current cervical pathology and no skin infection or shoulder lesion.

Interventions:

External-rotation exercises without a towel roll (0° shoulder abduction) and with a towel roll (30° shoulder abduction) were performed in a standing and side-lying.

Main Outcome Measures:

Maximal voluntary isometric contraction for the infraspinatus, middle and posterior deltoid, and pectoralis major and external rotation in standing and side-lying with and without a towel roll were performed. Normalized average and peak surface EMG amplitude were compared between the towel conditions during standing and side-lying external rotation.

Results:

Both infraspinatus and pectoralis major activity had no significant differences between the towel conditions in standing and side-lying (P > .05). In standing and side-lying, posterior-deltoid activity was significantly greater with a towel roll (P < .05). Middle-deltoid activity had no significant differences between the towel conditions in standing (P > .05). However, in side-lying, middle-deltoid activity was significantly lower with a towel roll (P < .05).

Conclusion:

Middle-deltoid activity decreased with a towel roll during side-lying exercises. More data are needed to determine if a towel roll could be used to potentially reduce superior glide during external-rotation exercises.

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Michael Sanders, Anton E. Bowden, Spencer Baker, Ryan Jensen, McKenzie Nichols and Matthew K. Seeley

Context: Foot and ankle injuries are common and often require a nonweight-bearing period of immobilization for the involved leg. This nonweight-bearing period usually results in muscle atrophy for the involved leg. There is a dearth of objective data describing muscle activation for different ambulatory aids that are used during the aforementioned nonweight-bearing period. Objective: To compare activation amplitudes for 4 leg muscles during (1) able-bodied gait and (2) ambulation involving 3 different ambulatory aids that can be used during the acute phase of foot and ankle injury care. Design: Within-subject, repeated measures. Setting: University biomechanics laboratory. Participants: Sixteen able-bodied individuals (7 females and 9 males). Intervention: Each participant performed able-bodied gait and ambulation using 3 different ambulatory aids (traditional axillary crutches, knee scooter, and a novel lower-leg prosthesis). Main Outcome Measure: Muscle activation amplitude quantified via mean surface electromyography amplitude throughout the stance phase of ambulation. Results: Numerous statistical differences (P < .05) existed for muscle activation amplitude between the 4 observed muscles, 3 ambulatory aids, and able-bodied gait. For the involved leg, comparing the 3 ambulatory aids: (1) knee scooter ambulation resulted in the greatest vastus lateralis activation, (2) ambulation using the novel prosthesis and traditional crutches resulted in greater biceps femoris activation than knee scooter ambulation, and (3) ambulation using the novel prosthesis resulted in the greatest gastrocnemius activation (P < .05). Generally speaking, muscle activation amplitudes were most similar to able-bodied gait when subjects were ambulating using the knee scooter or novel prosthesis. Conclusions: Type of ambulatory aid influences muscle activation amplitude. Traditional axillary crutches appear to be less likely to mitigate muscle atrophy during the nonweighting, immobilization period that often follows foot or ankle injuries. Researchers and clinicians should consider these results when recommending ambulatory aids for foot or ankle injuries.

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Jihong Park, W. Matt Denning, Jordan D. Pitt, Devin Francom, J. Ty Hopkins and Matthew K. Seeley

Context:

Although knee pain is common, some facets of this pain are unclear. The independent effects (ie, independent from other knee injury or pathology) of knee pain on neural activation of lower-extremity muscles during landing and jumping have not been observed.

Objective:

To investigate the independent effects of knee pain on lower-extremity muscle (gastrocnemius, vastus medialis, medial hamstrings, gluteus medius, and gluteus maximus) activation amplitude during landing and jumping, performed at 2 different intensities.

Design:

Laboratory-based, pretest, posttest, repeated-measures design, where all subjects performed both data-collection sessions.

Methods:

Thirteen able-bodied subjects performed 2 different land and jump tasks (forward and lateral) under 2 different conditions (control and pain), at 2 different intensities (high and low). For the pain condition, experimental knee pain was induced via a hypertonic saline injection into the right infrapatellar fat pad. Functional linear models were used to evaluate the influence of experimental knee pain on muscle-activation amplitude throughout the 2 land and jump tasks.

Results:

Experimental knee pain independently altered activation for all of the observed muscles during various parts of the 2 different land and jump tasks. These activation alterations were not consistently influenced by task intensity.

Conclusion:

Experimental knee pain alters activation amplitude of various lower-extremity muscles during landing and jumping. The nature of the alteration varies between muscles, intensities, and phases of the movement (ie, landing and jumping). Generally, experimental knee pain inhibits the gastrocnemius, medial hamstring, and gluteus medius during landing while independently increasing activation of the same muscles during jumping.

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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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Alyssa Evans, Gavin Q. Collins, Parker G. Rosquist, Noelle J. Tuttle, Steven J. Morrin, James B. Tracy, A. Jake Merrell, William F. Christensen, David T. Fullwood, Anton E. Bowden and Matthew K. Seeley

Background: Physical activity and corresponding energy expenditure can improve health in various ways. Existing methods to directly measure energy expenditure are currently limited to laboratory settings and/or expensive instrumentation. The purpose of this study was to evaluate accuracy of energy expenditure characterization, during walking and running, using demographic data, as well as data collected via an accelerometer and novel piezoresponsive foam sensors. Methods: 30 individuals (14 females; mass = 67 ± 10 kg; height = 1.74 ± 0.08 m; age = 23 ± 3 yrs) walked and ran at five speeds (1.34, 2.23, 2.68, 3.13, and 3.58 m/s) on a force-instrumented treadmill while wearing a metabolic analyzer and standardized athletic shoes instrumented with an accelerometer, and four novel nanocomposite piezoresponsive force sensors. Various predictive models, including demographic data and data derived from the accelerometer and force sensors, were evaluated for each gait speed. Results: The predictive models varied in ability to accurately characterize energy expenditure. For walking, the most accurate model included acceleration and body weight, and resulted in an average absolute error of 0.07 ± 0.03 kcal/min. For running, the most accurate model included sensor and acceleration data, and resulted in an average absolute error of 0.45 ± 0.14 kcal/min. Conclusions: When combined with acceleration data and body weight, the novel foam sensors can be used to inexpensively and accurately measure walking and running energy expenditure. This can be done at various speeds, outside of a traditional research laboratory. These results have application within a wide range of diverse contexts.