Efficacy of an Audio-Based Biofeedback Intervention to Modify Running Gait in Female Runners.

CONTEXT: A variety of gait retraining interventions are available to modify running mechanics associated with musculoskeletal injuries. These often require specialized equipment and/or personnel to prompt the runner toward specific strategies. OBJECTIVE: To determine whether instructing female recreational runners to "run quietly" could decrease impact force characteristics. DESIGN: Cohort. SETTING: Research laboratory. PARTICIPANTS: Fifteen healthy female recreational runners (24 [7] y) volunteered. INTERVENTIONS: Baseline testing occurred on day 1 (baseline), a posttraining assessment occurred on day 2 (training), and a final assessment occurred 1 week after training on day 3 (follow-up). A smartphone decibel measuring app was used to provide biofeedback on the decibel level of foot strike on day 2 (training). MAIN OUTCOMES: Peak vertical force, impact transient, peak and average vertical loading rate, ground contact time, and running economy were collected on each day and compared via repeated-measures analyses of variance. RESULTS: Vertical ground reaction force was lower at follow-up (2.30 bodyweights [BW]) versus baseline (2.39 BW, P = .023) and training (2.34 BW, P = .047). Maximal loading rate decreased from baseline (69.70 BW·s-1) to training (62.24 BW·s-1, P = .021) and follow-up (60.35 BW·s-1, P = .031). There was no change in running economy. CONCLUSIONS: Our findings demonstrate that simple instructions to "run quietly" can yield immediate and sustained reductions in impact force profiles, which do not influence running economy.

Novice Users of a Bodyweight-Supporting Treadmill Require Familiarization.

CONTEXT: Previous work has demonstrated an improvement in running economy during sustained running on a lower body positive pressure treadmill, but neuromuscular and spatiotemporal measures have only been investigated during short-duration running bouts on these devices. The current study sought to replicate the noted metabolic response and investigate whether neuromuscular and/or spatiotemporal adaptations underlie the noted improvements in running economy. DESIGN: Cross-sectional. METHODS: Fifteen trained runners (11 males and 4 females) ran three 15-minute trials with 30% bodyweight support at 70% of the speed that elicited their peak oxygen consumption while running on a standard treadmill. A series of 1-way analyses of variance with repeated measures were used to explore differences in dependent variables over the 45 minutes of running. Dependent variables included oxygen consumption, root-mean-square electromyography of the vastus medialis and medial gastrocnemius during stance, and spatiotemporal parameters. RESULTS: Oxygen consumption decreased after the initial exposure, with no further reductions after 20 minutes. Root-mean-square electromyography of the vastus medialis and medial gastrocnemius also decreased over time, with no further reductions after 20 and 10 minutes, respectively. No differences in spatiotemporal parameters were found. CONCLUSIONS: Future research should provide sufficient time for runners to develop a more economical gait pattern prior to collecting dependent variables, and previous findings using lower body positive pressure treadmills may need to be reconsidered. Athletes using these devices for training or rehabilitation should note that increased economy will lower the intensity of a given treadmill setting over time.

Making the Grade: An Exploration of Incline Running on a Bodyweight-Supportive Treadmill.

CONTEXT: Bodyweight-supporting treadmills are popular rehabilitation tools for athletes recovering from impact-related injuries because they reduce ground reaction forces during running. However, the overall metabolic demand of a given running speed is also reduced, meaning athletes who return to competition after using such a device in rehabilitation may not be as fit as they had been prior to their injury. OBJECTIVE: To explore the metabolic effects of adding incline during bodyweight-supported treadmill running. DESIGN: Cross-sectional. SETTING: Research laboratory. PARTICIPANTS: Fourteen apparently healthy, recreational runners (6 females and 8 males; 21 [3] y, 1.71 [0.08] m, 63.11 [6.86] kg). INTERVENTIONS: The participants performed steady-state running trials on a bodyweight-supporting treadmill at 8.5 mph. The control condition was no incline and no bodyweight support. All experimental conditions were at 30% bodyweight support. The participants began the sequence of experimental conditions at 0% incline; this increased to 1%, and from there on, 2% incline increases were introduced until a 15% grade was reached. Repeated-measures analysis of variance was used to compare all bodyweight-support conditions against the control condition. MAIN OUTCOME MEASURES: Oxygen consumption, heart rate, and rating of perceived exertion. RESULTS: Level running with 30% bodyweight support reduced oxygen consumption by 21.6% (P < .001) and heart rate by 12.0% (P < .001) compared with the control. Each 2% increase in incline with bodyweight support increased oxygen consumption by 6.4% and heart rate by 3.2% on average. A 7% incline elicited similar physiological measures as the unsupported, level condition. However, the perceived intensity of this incline with bodyweight support was greater than the unsupported condition (P < .001). CONCLUSIONS: Athletes can maintain training intensity while running on a bodyweight-supporting treadmill by introducing incline. Rehabilitation programs should rely on quantitative rather than qualitative data to drive exercise prescription in this modality.

Setting boundaries: Utilization of time to boundary for objective evaluation of the balance error scoring system.

Subjective evaluations of balance performance, like the modified Balance Error Scoring System (mBESS), are highly popular. Alternatively, quantitative measures may offer additional clarity in identifying balance dysfunction. A novel measure to define balance impairments is time to boundary (TTB), which represents the amount of time available to make corrective postural adjustments prior to the centre of pressure (CoP) reaching the edge of the base of support. The purpose of this investigation was to assess TTB and traditional measures of CoP displacement of young adults performing the mBESS on a BTrackS balance plate. Path length and TTB were calculated in anterior-posterior (AP) and medio-lateral (ML) directions, respectively. AP and ML path lengths were largest in Single stance (109.2 & 118.1 cm, respectively) and smallest in Dual stance (27.1 & 36.4 cm, respectively). The average AP and ML TTBs were higher in Dual (10.67 & 7.27 s, respectively) compared to Single (3.54 & 1.20 s, respectively) or Tandem (10.11 & 1.94 s, respectively) stances, and lower in Single stance compared to Tandem. Given the effect sizes for TTB were greater than those of path length in both directions, TTB more adequately differentiates these stance conditions than path length or subjective scores.

Averaging Trials Versus Averaging Trial Peaks: Impact on Study Outcomes.

Gait data are commonly presented as an average of many trials or as an average across participants. Discrete data points (eg, maxima or minima) are identified and used as dependent variables in subsequent statistical analyses. However, the approach used for obtaining average data from multiple trials is inconsistent and unclear in the biomechanics literature. This study compared the statistical outcomes of averaging peaks from multiple trials versus identifying a single peak from an average profile. A series of paired-samples t tests were used to determine whether there were differences in average dependent variables from these 2 methods. Identifying a peak value from the average profile resulted in significantly smaller magnitudes of dependent variables than when peaks from multiple trials were averaged. Disagreement between the 2 methods was due to temporal differences in trial peak locations. Sine curves generated in MATLAB confirmed this misrepresentation of trial peaks in the average profile when a phase shift was introduced. Based on these results, averaging individual trial peaks represents the actual data better than choosing a peak from an average trial profile.

A static posturography guide to implementing time-to-boundary.

The emergence of time-to-boundary provides an advanced representation of the spatiotemporal characteristics of postural control through the estimation of the time required for the center of pressure to reach the boundary of the base of support. Time-to-boundary has demonstrated its utility in several healthy and clinical adoptions; however, unknown inconsistencies among studies exist. Text and graphical representations understandably highlight idealistic standards, but new investigators to this measure are forced to wade through the same potential pitfalls that others have addressed, but the field has neglected to concatenate. The purpose of this communication is to share recent methodological advancements made to enhance time-to-boundary and describe the components of the time-to-boundary code that is being made publicly accessible for the first time. We anticipate future researchers who wish to apply this methodology to their data processing toolbox could utilize our script in full, with any deviations in potential future developments noted in clear fashion. Historically, researchers (including ourselves) have had to interpret text-based descriptions of the existing literature into quantitative steps in a computational mathematics script. In contrast to fixed process measures that do not require investigator input (e.g., path length), time-to-boundary poses two distinct but connected challenges to investigators. The coding process itself can be a hurdle for novices or practitioners. Second, transferring logical considerations such as robust, objective event detection routines must be defended in the review process. This comprehensive guide to time-to-boundary, as used in our applications, should enhance adoption and advance the comprehension of postural control.

Good times, bad times? An evaluation of event detection strategies in time to boundary postural assessments.

Time-to-boundary (TtB) is a popular balance metric that identifies minimum reaction times available to correct balance challenges during quiet standing. Minimum event criteria is a critical methodological consideration to determine physiologically relevant TtB outcomes yet selection methodology appears inconsistent and/or vaguely defined across studies. This study aimed to identify a robust, objective methodology to select meaningful TtB outcomes. Ninety-seven healthy adults stood quietly on a force platform with eyes open and feet together. Anterior-posterior (AP) and medial-lateral (ML) center-of-pressure data from 150 s were utilized to compute a TtB series. The MATLAB findpeaks function identified minima with and without a time delay following selected events and/or a vertical axis threshold. An individualized time delay excluded excessively large values that hold no clinically relevant information, and this effect was enhanced by a vertical threshold at 22 s. The absolute minimum TtB was unaffected by any findpeaks criteria. The recommendations implicated by these results will help improve clarity and consistency among TtB studies, thereby enhancing the applicability of clinical findings.

Characterization of trial duration in traditional and emerging postural control measures.

Researchers may select from varied technological and practical options when evaluating balance. Methodological choices inform the quantitative outcomes observed and allow practitioners to diagnose balance abnormalities. Past investigations have differed widely on sampling duration, and these discrepancies hinder comparisons among studies and confidence in outcomes where trials were excessively short. This study aimed to identify necessary trial lengths for common and emerging center of pressure-based measures. We hypothesized that dependent variables would fluctuate over time but eventually reach a stable magnitude. Ninety-seven apparently healthy adults performed quiet standing for 180-seconds (s) with eyes (A) open and (B) closed on a force platform. Anterior-posterior and medial-lateral elements of the center of pressure were used to calculate velocity, time-to-boundary, and Hurst exponents using 15, 30, 90, 120, 150, and 180 s of data. Two-way repeated measures ANOVAs were used to differentiate postural measures over time and between vision conditions. Outcomes were considered stable when significant changes in the measure were no longer observed in the time factor. Dependent measures stabilized for velocity between 60 and 120 s, time-to-boundary between 120 and 150 s, and the Hurst exponent between 30 and 120 s. Velocity measures stabilized quicker with eyes open, whereas vision had no effect or the eyes closed condition was faster to stabilize in time-to-boundary and detrended fluctuation analysis measures. We conclude that 150 s of standing data is sufficient to capture a broad range of postural stability outcomes regardless of vision condition.

Bodyweight support alters the relationship between preferred walking speed and cost of transport.

Humans tend to select a preferred walking speed (PWS) that minimizes the metabolic energy consumed per distance traveled, i.e. the Cost of Transport (CoT). The aims of this study were to: 1. compare PWS overground vs. on a treadmill at 100 and 50% of body weight, and 2. explore whether with body weight support, PWS corresponds to the speed that minimizes CoT. Fifteen healthy adults walked overground and on a lower body positive pressure treadmill with and without bodyweight support. Walking speeds (m.s-1) were recorded for each condition. Rate of energy expenditure (J.kg-1.min-1) and CoT (J.kg-1.m-1) were then determined from 5-min walking trials with 50% bodyweight support at PWS and ± 30% of the self-selected walking speed for that condition. PWS did not differ across conditions. With 50% body weight support, for each 30% increase in walking speed, rates of metabolic energy expenditure increased ∼15% while CoT decreased by ∼14%. Thus, with 50% body weight support, PWS did not correspond with the speed that minimized CoT. Bodyweight support decreases cost of maintaining an upright body but does not decrease the metabolic demand of limb advancement, contributing to the linear yet not proportional changes in rates of energy expenditure and CoT. We conclude that bodyweight support via an AlterG® treadmill disconnects the association between PWS and minimum CoT. These findings have implications for clinical populations (e.g., obese, elderly) who may benefit from walking on a bodyweight supporting treadmill but may select speeds incompatible with their physical activity goals.

Relationships between Physiological and Self-Reported Assessment of Cancer-Related Fatigue.

The purpose of this study was to evaluate the relationships between subjective, self-reported cancer related fatigue (CRF) and objective measures of muscular strength and fatigability in cancer survivors. A total of 155 cancer survivors (60 ± 13 years of age) completed a questionnaire for the assessment of CRF, along with assessments of handgrip strength, quadriceps strength and fatigability (reduced force/torque). Fatigability was measured by completing 15 maximal isokinetic contractions of the knee extensors (QFI). Spearman's rho correlation coefficients were calculated as pairwise combinations of the numerical and categorical dependent measures. Categorical variables were analyzed via nonparametric means of association. This included a 4×4 chi-square to test whether cancer stage (0-4) was independent of fatigue status (none, mild, moderate, severe) and whether cancer treatment (surgery, radiation, chemotherapy, or combinations of these) was independent of fatigue status. None of the physiological strength and fatigue measures were significantly correlated to overall perceived fatigue or any of the subscales. Cancer stage and treatment type were also not significantly related to fatigue status (likelihood ratio = .225, Cramer's V = .228; likelihood ratio = .103, Cramer's V = .369, respectively). Our results show that levels of patient reported fatigue severity were not significantly related to muscular fatigability or strength. As a result, cancer patients experiencing fatigue may benefit from following the standard exercise guidelines for cancer survivors, regardless of their levels of self-reported fatigue.

Obese adults walk differently in shoes than while barefoot.

BACKGROUND: Some comparisons between walking gait of obese and non-obese adults have been made during barefoot conditions, and others while shod. Methodological differences, footwear conditions, and gait speed disparities among the research done on overweight individuals were the factors motivating the present study. RESEARCH QUESTION: The present study was designed to compare gait kinematics and kinetics of obese adults between two footwear conditions (barefoot versus shod) at a set walking speed. METHODS: Ten obese (body mass index > 30 kg.m-2), but otherwise healthy adults (age = 26 ±â€¯3 years, height = 1.79 ±â€¯0.10 m, mass = 108.46 ±â€¯13.25 kg) participated in this study. Ground reaction forces and 3D kinematic data were simultaneously collected as participants walked overground at 1.5 m.s-1 in barefoot and shod conditions. RESULTS: Walking barefoot reduced ankle, knee, and hip ranges of motion, and stride length, stance time, and double support time were also reduced. Kinetic outcomes included smaller peak vertical and anterior-posterior ground reaction forces and knee joint moments while barefoot. SIGNIFICANCE: Footwear condition significantly influences key gait variables in obese adults. Conflicting conclusions from previous investigations of gait in obese adults may be a consequence of differing footwear conditions.

Leveling the playing field: Evaluation of a portable instrument for quantifying balance performance.

Balance is a complex, sensorimotor task requiring an individual to maintain the center of gravity within the base of support. Quantifying balance in a reliable and valid manner is essential to evaluating disease progression, aging complications, and injuries in clinical and research settings. Typically, researchers use force plates to track motion of the center of gravity during a variety of tasks. However, limiting factors such as cost, portability, and availability have hindered postural stability evaluation in these settings. This study compared the "gold standard" for assessing postural stability (i.e., the laboratory-grade force plate) to a more affordable and portable assessment tool (i.e., BTrackS balance plate) in healthy young adults. Correlations and Bland-Altman plots between the center of pressure outcome measures derived from these two instruments were produced. Based on the results of this study, the measures attained from the portable balance plate objectively quantified postural stability with high validity on both rigid and compliant surfaces, demonstrated by thirty-five out of thirty-eight observed postural stability metrics in both surface conditions with a correlation of 0.98 or greater. The low cost, portable system performed similarly to the lab-grade force plate indicating the potential for practitioners and researchers to use the BTrackS balance plate as an alternative to the more expensive force plate option for assessing postural stability, whether in the lab setting or in the field.

Effects of load carriage and footwear on lower extremity kinetics and kinematics during overground walking.

Kinetic and kinematic responses during walking vary by footwear condition. Load carriage also influences gait patterns, but it is unclear how an external load influences barefoot walking. Twelve healthy adults (5 women, 7 men) with no known gait abnormalities participated in this study (age=23±3years, height=1.73±0.11m, and mass=70.90±12.67kg). Ground reaction forces and 3D motion were simultaneously collected during overground walking at 1.5ms-1 in four conditions: Barefoot Unloaded, Shod Unloaded, Barefoot Loaded, and Shod Loaded. Barefoot walking reduced knee and hip joint ranges of motion, as well as stride length, stance time, swing time, and double support time. Load carriage increased stance and double support times. The 15% body weight load increased GRFs ∼15%. Walking barefoot reduced peak anteroposterior GRFs but not peak vertical GRFs. Load carriage increased hip, knee, and ankle joint moments and powers, while walking barefoot increased knee and hip moments and powers. Thus, spatiotemporal and kinematic adjustments to walking barefoot decrease GRFs but increase knee and hip kinetic measures during overground walking. The ankle seems to be less affected by these footwear conditions. Regardless of footwear, loading requires larger GRFs, joint loads, and joint powers.

Effects of load carriage and footwear on spatiotemporal parameters, kinematics, and metabolic cost of walking.

Gait patterns are commonly altered when walking or running barefoot compared to shod conditions. Although controversy exists as to whether barefoot conditions result in lower metabolic costs, it is clear that adding load to the body results in increased metabolic costs. The effects of footwear and backpack loading have been investigated separately, but it is unclear whether manipulating both simultaneously would cause similar outcomes. Twelve healthy individuals (7 female, 5 male) with no obvious gait abnormalities participated in this study (age=24±2 years, height=1.73±0.13 m, and mass=71.1±16.9 kg). Steady state metabolic data and 3D motion capture were collected during treadmill walking at 1.5 ms(-1) in four conditions: Barefoot Unloaded, Shod Unloaded, Barefoot Loaded, and Shod Loaded. Barefoot walking elicited shorter stride lengths, stance and double support times, as well as a slight (≈1%), but not significant, decrease in metabolic cost. Loading increased metabolic costs of walking but did not elicit spatiotemporal changes in either footwear condition. Lower limb kinematic differences were noted in response to both loading and footwear. Changes in spatiotemporal parameters observed when walking barefoot were not exacerbated by the addition of a backpack load. This suggests that the increased metabolic demand associated with the load is met with a similar spatiotemporal pattern whether a person wears a supportive shoe or not. Thus, the discomfort associated with foot strike while barefoot that promotes spatiotemporal changes seems to be independent of load.