Runners' responses to a biofeedback intervention aimed to reduce tibial acceleration differ within and between individuals.

An increment in peak tibial acceleration (PTA) may be related to an increased risk of running-rated injury. Many authors believe that reducing PTA through improved shock-absorption could, therefore, help prevent injury. The aim of the current study was, therefore, to investigate the individual responses of participants to a biofeedback intervention aimed at reducing PTA.11 participants (two females, nine males; 43 ±â€¯10 years; stature: 1.74 ±â€¯0.07 m; body mass: 74 ±â€¯11 kg; distance running a week: 19 ±â€¯14 km; 5 km time: 24 ±â€¯3 min) received an intervention of six sessions of multisensory biofeedback aimed at reducing PTA. Mean PTA and kinematic patterns were measured at baseline, directly after the feedback intervention and a month after the end of the intervention. Group as well as single-subject analyses were performed to quantify differences between the sessions. A significant decrease of 26 per cent (effect size: Hedges' g = 0.94) in mean PTA was found a month after the intervention. No significant changes or large effect sizes were found for any group differences in the kinematic variables. However, on an individual level, shock-absorbing solutions differed both within and between participants. The data suggest participants did not learn a specific solution to reduce PTA but rather learned the concept of reducing PTA. These results suggest future research in gait retraining should investigate individual learning responses and focus on the different strategies participants use both between and within sessions. For training purposes, participants should not focus on learning one running strategy, but they should explore several strategies.

Coordination variability reveals the features of the 'independent seat' in competitive dressage riders.

The rider's ability to consistently coordinate their movements to their horse is a key determinant of performance in equestrian sport. This study investigated the inter-segmental coordination variability between the vertical displacement of a riding simulator and the pitch rotation of 28 competitive female dressage riders' head, trunk, pelvis, and left foot, in simulated medium and extended trot. A statistical non-parametric mapping three-way repeated-measures ANOVA investigated the influence of gait, competition level and segment on coordination variability. There was a significant main effect of gait and segment (p = 0.05), however, no significant effect of competition level. In medium trot, simulator-pelvis coupling was significantly (p < 0.001) less variable than simulator-head, -trunk, and -foot couplings. Significantly greater coordination variability of simulator-head and -foot relative to the trunk and pelvis suggested that riders can maintain stability in the saddle with their trunk and pelvis while allowing greater variability of their head and foot coupling to the simulator's vertical displacement. It is proposed that stronger coupling of the rider's pelvis relative to their other segments is one facet of the equestrian dressage skill of the independent seat. However, greater perturbations during simulated extended trot may necessitate a decrease in the independence of the rider's seat.

The use of biofeedback for gait retraining: A mapping review.

BACKGROUND: Biofeedback seems to be a promising tool to improve gait outcomes for both healthy individuals and patient groups. However, due to differences in study designs and outcome measurements, it remains uncertain how different forms of feedback affect gait outcomes. Therefore, the aim of this study is to review primary biomechanical literature which has used biofeedback to alter gait-related outcomes in human participants. METHODS: Medline, Cinahl, Cochrane, SPORTDiscus and Pubmed were searched from inception to December 2017 using various keywords and the following MeSHterms: biofeedback, feedback, gait, walking and running. From the included studies, sixteen different study characteristics were extracted. FINDINGS: In this mapping review 173 studies were included. The most common feedback mode used was visual feedback (42%, n = 73) and the majority fed-back kinematic parameters (36%, n = 62). The design of the studies was poor: only 8% (n = 13) of the studies had both a control group and a retention test; 69% (n = 120) of the studies had neither. A retention test after 6 months was performed in 3% (n = 5) of the studies, feedback was faded in 9% (n = 15) and feedback was given in the field rather than the laboratory in 4% (n = 8) of the studies. INTERPRETATION: Further work on biofeedback and gait should focus on the direct comparison between different modes of feedback or feedback parameters, along with better designed and field based studies.

Effects of running retraining on biomechanical factors associated with lower limb injury.

Injury risk is an important concern for runners; however, limited evidence exists regarding changes to injury risk following running style retraining. Biomechanical factors, such as absolute peak free moment, knee abduction impulse, peak foot eversion and foot eversion excursion, have been shown to predict lower limb injury. The aim of this study was to assess the effects of Pose running retraining on biomechanical factors associated with lower limb running injury. Twenty uninjured recreational runners were pair-matched based on their five km run time performance and randomly assigned to control (n = 10) and intervention (three 2-h Pose running retraining sessions) groups (n = 10). Three dimensional kinetic and kinematic data were collected from all participants running at relative (REL: 1.5 km·h-1 below respiratory compensation point) and absolute (ABS: 4.5 m·s-1) speeds. Biomechanical factors associated with lower limb injury, as well as selected kinematic variables (to aid interpretation), were assessed. Following a six-week, non-coached time-period, all assessments were repeated. No changes to the biomechanical factors associated with lower limb injury examined in this study were observed (P > .05). Intervention group participants (presented as pre- and post-intervention respectively) exhibited an increased foot strike index (REL speed: 21.79-42.66%; ESW = 4.73; P = .012 and ABS speed: 22.38-46.98%; ESW = 2.83; P = .008), reduced take-off distance (REL speed: -0.35 to -0.32 m; ESW = 0.75; P = .012), increased knee flexion at initial contact (REL speed: -14.11 to -18.50°; ESW = -0.88; P = .003), increased ankle dorsiflexion at terminal stance (REL speed: -33.61 to -28.35°; ESW = 1.57; P = .036) and reduced stance time (ABS speed: 0.21-0.19 s; ESW = -0.85; P = .018). Finally, five km run time did not change (22:04-22:19 min; ESW = 0.07; P = .229). It was concluded that following Pose running retraining, retrained participants adopted a running style that was different to their normal style without changing specific, biomechanical factors associated with lower limb injury or compromising performance.

An integrated approach to the biomechanics and motor control of cricket fast bowling techniques.

To date, scientific investigations into the biomechanical aspects of cricket fast bowling techniques have predominantly focused on identifying the mechanical factors that may predispose fast bowlers to lower back injury with a relative paucity of research being conducted on the technical features that underpin proficient fast bowling performance. In this review paper, we critique the scientific literature examining fast bowling performance. We argue that, although many published investigations have provided some useful insights into the biomechanical factors that contribute to a high ball release speed and, to a lesser extent, bowling accuracy, this research has not made a substantive contribution to knowledge enhancement and has only had a very minor influence on coaching practice. To significantly enhance understanding of cricket fast bowling techniques and, therefore, have greater impact on practice, we recommend that future scientific research adopts an interdisciplinary focus, integrating biomechanical measurements with the analytical tools and concepts of dynamical systems motor control theory. The use of qualitative (topological) analysis techniques, in particular, promises to increase understanding of the coordinative movement patterns that define 'technique' in cricket fast bowling and potentially help distinguish between functional and dysfunctional aspects of technique for individual fast bowlers.

Between-day reliability of time-to-contact measures used to assess postural stability.

Traditional measures of postural stability consider movement of the center of pressure (COP) or the center of mass (COM) without regard to the boundary of support (BOS). A potentially more appropriate measure is postural time-to-contact (TtC) which defines the spatio-temporal proximity of the COM or COP to the BOS. Given the increasing popularity of TtC measures, it is important to determine their reliability. Therefore, the purpose of this study was to determine the effects of the number of trials and trial duration on the reliability of postural TtC measures. COP data were collected (100 Hz) in 16 young healthy participants during 10 trials (60-s duration) of quiet standing with eyes open on two occasions - seven days apart. Postural TtC of each trial was calculated using two different methods. The intersession reliability of the TtC measures was assessed by calculating between session intraclass correlation coefficients (ICC(2,1)) using different combinations of the number of trials (1-10) and trial duration (10, 20, 30, 40, 50 and 60s). Both TtC methods were very reliable. Additionally, both measures of TtC were more reliable than the standard deviation of the anterior-posterior COP and slightly more reliable than path length. This difference was most pronounced when fewer and shorter trials were used.

Relative phase coordination analysis in the assessment of dynamic gait symmetry.

A variety of kinematic and kinetic measures are typically used to examine gait symmetry. Here we make the argument that gait asymmetries may be most clearly revealed through higher-order coordinative measures such as continuous relative phase (CRP). Participants walked on a treadmill with a load attached to their nondominant limb. Gait symmetry was then assessed using spatial (angular), temporal (velocity), and higher-order (CRP) symmetry measures. It was found that higher-order measures were most sensitive at assessing asymmetries due to load manipulation at both the distal and proximal segments. Symmetry measures derived from velocity variables were more sensitive than angular measures at detecting asymmetries, but were less sensitive compared with CRP. Asymmetries were also more readily detected using segmental angles compared with joint angles. These results suggest that gait asymmetries that emerge from changing constraints manifest along both spatial and temporal dimensions.

Developmental changes in the dynamical structure of postural sway during a precision fitting task.

Recent research using measures to assess the time-dependent structure of postural fluctuations has provided new insights into the stability and adaptability of human postural control in adults. To date, little research has examined how postural dynamics reflecting the stability and adaptability of postural control may change as a function of development, especially during supra-postural tasks. The goal of this study was to examine the dynamics of postural fluctuations during a manual-fitting task in which precision, visual and postural task constraints were altered in children and adults. Three age groups were tested: 7-, 10-year olds and college aged adults. Recurrence quantification analysis (RQA) was used to assess the regularity (percent determinism) and complexity (entropy) of the center of pressure (CoP) in the anterior-posterior (AP) and medial-lateral (ML) directions. The CoP patterns exhibited by adults were more deterministic and more complex (higher entropy) than those of the 7-year-old children under the different experimental manipulations. No differences between the adults and the 10-year-old children were observed. The increase in determinism with a corresponding increase in entropy exhibited by the adults and older-children during a manual fitting task may be a prospective mechanism over which postural movements follow a more predictable path allowing for stable and flexible task performance. Our results also support the notion that complex postural fluctuations (as measured by RQA entropy) are functional and typically increase as the precision requirements of a manual task increase.