Spatiotemporal characteristics of spontaneous overground walk-to-run transition

Wearable technology assessing running biomechanics and prospective running-related injuries in Active Duty Soldiers

The purpose of this study was to determine if running biomechanical variables measured by wearable technology were prospectively associated with running injuries in Active Duty Soldiers. A total of 171 Soldiers wore a shoe pod that collected data on running foot strike pattern, step rate, step length and contact time for 6 weeks. Running-related injuries were determined by medical record review 12 months post-study enrollment. Differences in running biomechanics between injured and non-injured runners were compared using independent t-tests or ANCOVA for continuous variables and chi-square analyses for the association of categorical variables. Kaplan-Meier survival curves were used to estimate the time to a running-related injury. Risk factors were carried forward to estimate hazard ratios using Cox proportional hazard regression models. Forty-one participants (24%) sustained a running-related injury. Injured participants had a lower step rate than non-injured participants, but step rate did not have a significant effect on time to injury. Participants with the longest contact time were at a 2.25 times greater risk for a running-related injury; they were also relatively slower, heavier, and older. Concomitant with known demographic risk factors for injury, contact time may be an additional indicator of a running-related injury risk in Active Duty Soldiers.

Maltodextrin-Based Carbohydrate Oral Rinsing and Exercise Performance: Systematic Review and Meta-Analysis

Background

Carbohydrates are an important fuel for optimal exercise performance during moderate- and high-intensity exercise; however, carbohydrate ingestion during high-intensity exercise may cause gastrointestinal upset. A carbohydrate oral rinse is an alternative method to improve exercise performance in moderate- to high-intensity exercise with a duration of 30–75 min. This is the first systematic review and meta-analysis to comprehensively examine the isolated effect of maltodextrin-based rinsing on exercise performance.

Objective

The objective of this review was to establish the effect of a maltodextrin-based carbohydrate oral rinse on exercise performance across various modes of exercise. Furthermore, a secondary objective was to determine the effects of moderators [(1) participant characteristics; (2) oral rinse protocols; (3) exercise protocol (i.e. cycling, running etc.) and (4) fasting] on exercise performance while using a maltodextrin-based, carbohydrate oral rinse.

Methods

Five databases (MEDLINE, PsycINFO, Embase, SPORTDiscus and Global Health) were systematically searched for articles up to March 2021 and screened using Covidence (a systematic review management tool). A random effects robust meta-analysis and subgroup analyses were performed using Stata Statistical Software: Release 16.

Results

Thirty-five articles met the inclusion criteria and were included in the systematic review; 34 of these articles were included in the meta-analysis. When using a conventional meta-analytic approach, overall, a carbohydrate oral rinse improved exercise performance in comparison with a placebo (SMD = 0.15, 95% CI 0.04, 0.27; p = 0.01). Furthermore, when implementing an adjusted, conservative, random effects meta-regression model using robust variance estimation, overall, compared with placebo, a carbohydrate oral rinse demonstrated evidence of improving exercise performance with a small effect size (SMD = 0.17, 95% CI − 0.01, 0.34; p = 0.051).

Conclusion

This systematic review and meta-analysis demonstrates that a maltodextrin-based carbohydrate oral rinse can improve exercise performance. When comparing the two meta-analytic approaches, although non-significant, the more robust, adjusted, random effects meta-regression model demonstrated some evidence of a maltodextrin-based carbohydrate oral rinse improving exercise performance overall.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-022-01658-3.

Age-dependent variability in spatiotemporal gait parameters and the walk-to-run transition

Adolescents tend to exhibit more variability in their gait patterns than adults, suggesting a lack of gait maturity during this period of ongoing musculoskeletal growth and development. However, there is a lack of consensus over the age at which mature gait patterns are achieved and the factors contributing to gait maturation. Therefore, the purpose of this study was to investigate gait control and maturity in adolescents by determining if differences existed between adolescents and adults in a) the amount of spatiotemporal variability of walking and running patterns across a range of speeds, and b) how swiftly gait patterns are adapted to increasing gait speed during the walk-to-run transition. Forty-six adolescents (10-12-year-olds, n = 17; 13-14-year-olds, n = 12; and 15-17-year-olds, n = 17) and 12 young adults completed an incrementally ramped treadmill test (+0.2 km·h^-1 every 30 s) to determine the preferred transition speed (PTS) during a walk-to-run transition. Age-related differences in the variability of stride lengths and stride durations were assessed across 4 speeds (self-selected walking speed, PTS - 0.06 m·s^-1, PTS + 0.06 m·s^-1, PTS + 0.83 m·s^-1). Repeated measures ANOVAs (p < 0.05) compared coefficients of variation for these spatiotemporal parameters, while a one-way ANOVA compared the numbers of gait transitions and speed increments used to identify PTS between the adolescent groups and young adults. Compared to adults, 10-12yo exhibited more spatiotemporal variability during all gait conditions, while 13-17yo only exhibited more variability at PTS + 0.06 m·s^-1. No age-dependent pattern was observed in PTS values, but 10-12yo completed more gait transitions over more speed increments than 15-17yo and adults. The development of mature gait patterns is thus a progressive process, with walking maturing at an earlier age than running. As 10-12yo were unable to swiftly adapt gait patterns to the changing task demands, their control mechanisms of gait may not have fully matured yet.

The role of stride frequency for walk-to-run transition in humans

It remains unclear why humans spontaneously shift from walking to running at a certain point during locomotion at gradually increasing velocity. We show that a calculated walk-to-run transition stride frequency (70.6 ± 3.2 strides min⁻¹) agrees with a transition stride frequency (70.8 ± 3.1 strides min⁻¹) predicted from the two stride frequencies applied during treadmill walking and running at freely chosen velocities and freely chosen stride frequencies. The agreement is based on Bland and Altman’s statistics. We found no essential mean relative difference between the two transition frequencies, i.e. −0.5% ± 4.2%, as well as limits of agreement of −8.7% and 7.7%. The particular two freely chosen stride frequencies used for prediction are considered behavioural attractors. Gait is predicted to be shifted from walking to running when the stride frequency starts getting closer to the running attractor than to the walking attractor. In particular, previous research has focussed on transition velocity and optimisation theories based on minimisation of, e.g., energy turnover or biomechanical loadings of the legs. Conversely, our data support that the central phenomenon of walk-to-run transition during human locomotion could be influenced by behavioural attractors in the form of stride frequencies spontaneously occurring during behaviourally unrestricted gait conditions of walking and running.

The effect of trial familiarisation on the validity and reproducibility of a field-based self-paced VO2max test

The self-paced maximal oxygen uptake (VO2max) test (SPV), which is based on the Borg 6-20 Ratings of Perceived Exertion (RPE) scale, allows participants to self-regulate their exercise intensity during a closed-loop incremental maximal exercise test. As previous research has assessed the utility of the SPV test within laboratory conditions, the purpose to this study was to assess the effect of trial familiarisation on the validity and reproducibility of a field-based, SPV test. In a cross-sectional study, fifteen men completed one laboratory-based graded exercise test (GXT) and three field-based SPV tests. The GXT was continuous and incremental until the attainment of VO2max. The SPV, which was completed on an outdoor 400m athletic track, consisted of five x 2 min perceptually-regulated (RPE11, 13, 15, 17 and 20) stages of incremental exercise. There were no differences in the VO2max reported between the GXT (63.5±10.1 ml·kg(-1)·min(-1)) and each SPV test (65.5±8.7, 65.4±7.0 and 66.7±7.7 ml·kg(-1)·min(-1) for SPV1, SPV2 and SPV3, respectively; P>.05). Similar findings were observed when comparing VO2max between SPV tests (P>.05). High intraclass correlation coefficients were reported between the GXT and the SPV, and between each SPV test (≥.80). Although participants ran faster and further during SPV3, a similar pacing strategy was implemented during all tests. This study demonstrated that a field-based SPV is a valid and reliable VO2max test. As trial familiarisation did not moderate VO2max values from the SPV, the application of a single SPV test is an appropriate stand-alone protocol for gauging VO2max.

The efficacy of a self-paced VO2max test during motorized treadmill exercise

PURPOSE

To assess the utility of a self-paced maximal oxygen uptake (VO2max) test (SPV) in eliciting an accurate measure of VO2max in comparison with a traditional graded exercise test (GXT) during motorized treadmill exercise.

DESIGN

This was a cross-sectional experimental study whereby recreationally trained men (n = 13, 25.5 ± 4.6 y) completed 2 maximal exercise tests (SPV, GXT) separated by a 72-h recovery period.

METHODS

The GXT was continuous and incremental, with prescribed 1-km/h increases every 2 min until the attainment of VO2max. The SPV consisted of 5 × 2-min stages of incremental exercise, which were self-selected and adjusted according to 5 prescribed RPE levels (RPE 11, 13, 15, 17, and 20).

RESULTS

Although no significant differences in VO2max were observed between the SPV and GXT (63.9 ± 3.3 cf 60.9 ± 4.6 mL · kg-1 · min-1, respectively, P > .05), the apparent 4.7% mean difference may be practically important. The 95% limits-of-agreement analysis was 3.03 ± 11.49 mL · kg-1 · min-1. Therefore, in the worst-case scenario, the GXT may underestimate measured VO2max as ascertained by the SPV by up to 19%. Conversely, the SPV could underestimate the GXT by 14%.

CONCLUSIONS

The current study has shown that the SPV is an accurate measure of VO2max during exercise on a motorized treadmill and may provide a slightly higher VO2max value than that obtained from a traditional GXT. The higher VO2max during the SPV may be important when prescribing training or monitoring athlete progression.

Gait and jogging parameters in people with minimally impaired multiple sclerosis

Increasing awareness of the significance of ambulatory limitations in people with multiple sclerosis (MS) requires a regular assessment of walking ability in order to monitor disease dynamics. However, it is questionable whether the standard tools are sufficiently sensitive to detect mobility deficits in patients who are minimally impaired. Therefore, the main objective of this study was to examine an extended assessment tool characterizing spatio-temporal parameters of gait and jogging in people with minimally impaired MS. Twenty relapsing remitting patients diagnosed with MS, 8 women and 12 men, aged 36.3 ± 9.2 y, EDSS mean score 1.8 ± 1.2, were recruited from the Multiple Sclerosis Center, Sheba Medical Center, Tel Hashomer, Israel to participate in the study. Twenty apparently healthy subjects (10 women and 10 men), aged 34.3 ± 7.4 years served as controls. Balance-, gait- and jogging-related spatio-temporal parameters were obtained using the Zebris FDM-T Treadmill (Zebris(®) Medical GmbH, Germany). Each subject completed a sequence of 3 jogging tests under different conditions. Gait and balance tests were performed prior and after jogging trials. When comparing gait evaluation, jogging revealed additional abnormalities in the MS group vs. the healthy controls. In addition to step time asymmetry and larger step width, jogging was associated with a slower self-selected velocity, shorter step length, longer stance phase and a prolonged double support phase. People minimally affected by MS have the ability to jog. However, clinician's should be aware of the possible deficits accompanying this popular activity.

Joint kinematics and kinetics of overground accelerated running versus running on an accelerated treadmill

Literature shows that running on an accelerated motorized treadmill is mechanically different from accelerated running overground. Overground, the subject has to enlarge the net anterior-posterior force impulse proportional to acceleration in order to overcome linear whole body inertia, whereas on a treadmill, this force impulse remains zero, regardless of belt acceleration. Therefore, it can be expected that changes in kinematics and joint kinetics of the human body also are proportional to acceleration overground, whereas no changes according to belt acceleration are expected on a treadmill. This study documents kinematics and joint kinetics of accelerated running overground and running on an accelerated motorized treadmill belt for 10 young healthy subjects. When accelerating overground, ground reaction forces are characterized by less braking and more propulsion, generating a more forward-oriented ground reaction force vector and a more forwardly inclined body compared with steady-state running. This change in body orientation as such is partly responsible for the changed force direction. Besides this, more pronounced hip and knee flexion at initial contact, a larger hip extension velocity, smaller knee flexion velocity and smaller initial plantarflexion velocity are associated with less braking. A larger knee extension and plantarflexion velocity result in larger propulsion. Altogether, during stance, joint moments are not significantly influenced by acceleration overground. Therefore, we suggest that the overall behaviour of the musculoskeletal system (in terms of kinematics and joint moments) during acceleration at a certain speed remains essentially identical to steady-state running at the same speed, yet acting in a different orientation. However, because acceleration implies extra mechanical work to increase the running speed, muscular effort done (in terms of power output) must be larger. This is confirmed by larger joint power generation at the level of the hip and lower power absorption at the knee as the result of subtle differences in joint velocity. On a treadmill, ground reaction forces are not influenced by acceleration and, compared with overground, virtually no kinesiological adaptations to an accelerating belt are observed. Consequently, adaptations to acceleration during running differ from treadmill to overground and should be studied in the condition of interest.

Mechanics of overground accelerated running vs. running on an accelerated treadmill

Unsteady state gait involving net accelerations has been studied overground and on a treadmill. Yet it has never been tested if and to what extent both set-ups are mechanically equal. This study documents the differences in ground reaction forces for accelerated running on an instrumented runway and running on an accelerating treadmill by building a theoretical framework which is experimentally put to the test. It is demonstrated that, in contrast to overground, no mean fore-after force impulse should be generated to follow an accelerating treadmill due to the absence of linear whole body acceleration. Accordingly, the adaptations in the braking phase (less braking) and propulsive phase (more propulsion) to accelerate overground are not present to follow an accelerating treadmill. It can be concluded that running on an accelerating treadmill is mechanically different from accelerated running overground.

Biomechanics of spontaneous overground walk-to-run transition

The purpose of the present study is to describe the biomechanics of spontaneous walk-to-run transitions (WRTs) in humans. After minimal instructions, 17 physical active subjects performed WRTs on an instrumented runway enabling measurement of speed, acceleration, spatiotemporal variables, ground reaction forces and 3D kinematics. The present study describes (1) the mechanical energy fluctuations of the body centre-of-mass (BCOM) as a reflection of the whole body dynamics and (2) the joint kinematics and kinetics. Consistent with previous research, the spatiotemporal variables show a sudden switch from walking to running in one transition step. During this step there is a sudden increase in forward speed, the so-called speed jump (0.42 m/s). At total body level, this is reflected in a sudden increase in energy of the BCOM (0.83 ± 0.14 J/kg) and an abrupt change from an out-of-phase to an in-phase organization of the kinetic and potential energy fluctuations. During the transition step a larger net propulsive impulse compared to the preceding and following steps is observed due to a decrease in the braking impulse. It is suggested that the altered landing configuration (prepared during the last 40% of the preceding swing) places the body in an optimal configuration to minimize this braking impulse. We hypothesize this configuration also evokes a reflex allowing a more powerful push off, which generates enough power to complete the transition and launch the first flight phase. This powerful push-off is also reflected in the vertical ground reaction force which suddenly changes to a running pattern.

Overground vs. treadmill walk-to-run transition

Determination of the walk-to-run transition (WRT) speed is a crucial aspect of gait transition research, which has been conducted on treadmill as well as overground. Overground WRT-speeds were reported to be higher than on treadmill. Part of this difference could be related to the lower acceleration magnitudes on treadmill. In this study, spontaneous WRT overground was compared to WRT at a comparable acceleration on treadmill. In addition, calculation procedures correcting for movement in the lab reference frame on treadmill were implemented. As such, this study was, in contrast to previous treadmill studies, able to detect a speed jump. This speed jump was until now a typical feature of overground WRT and contributed to the higher transition speed. By incorporating horizontal movements of the COM, a speed jump was also detected on treadmill. Yet, treadmill WRT-speed (2.61 ms(-1)) remained lower than overground (2.85 ms(-1)). Nevertheless, this difference was much smaller than assumed in the literature. The remaining difference could be explained by a larger speed jump (treadmill: 0.40 ms(-1); overground: 0.51 ms(-1)), and a higher speed at the start of the transition step overground (treadmill: 2.21 ms(-1); overground: 2.34 ms(-1)). In conclusion, even when controlling for effects of acceleration and movement in the lab reference frame a treadmill influence on WRT was visible.

Influence of treadmill acceleration on actual walk-to-run transition

When accelerating continuously, humans spontaneously change from a walking to a running pattern by means of a walk-to-run transition (WRT). Results of previous studies indicate that when higher treadmill accelerations are imposed, higher WRT-speeds can be expected. By studying the kinematics of the WRT at different accelerations, the underlying mechanisms can be unravelled. 19 young, healthy female subjects performed walk-to-run transitions on a constantly accelerating treadmill (0.1, 0.2 and 0.5 m s(-2)). A higher acceleration induced a higher WRT-speed, by effecting the preparation of transition, as well as the actual transition step. Increasing the acceleration caused a higher WRT-speed as a result of a greater step length during the transition step, which was mainly a consequence of a prolonged airborne phase. Besides this effect on the transition step, the direct preparation phase of transition (i.e. the last walking step before transition) appeared to fulfil specific constraints required to execute the transition regardless of the acceleration imposed. This highlights an important role for this step in the debate regarding possible determinants of WRT. In addition spatiotemporal and kinematical data confirmed that WRT remains a discontinuous change of gait pattern in all accelerations imposed. It is concluded that the walk-to-run transition is a discontinuous switch from walking to running which depends on the magnitude of treadmill belt acceleration.

Control of the upper body accelerations in young and elderly women during level walking

BACKGROUND

The control of the head movements during walking allows for the stabilisation of the optic flow, for a more effective processing of the vestibular system signals, and for the consequent control of equilibrium.In young individuals, the oscillations of the upper body during level walking are characterised by an attenuation of the linear acceleration going from pelvis to head level. In elderly subjects the ability to implement this motor strategy is reduced. The aim of this paper is to go deeper into the mechanisms through which the head accelerations are controlled during level walking, in both young and elderly women specifically.

METHODS

A stereophotogrammetric system was used to reconstruct the displacement of markers located at head, shoulder, and pelvis level while 16 young (age: 24 +/- 4 years) and 20 older (age: 72 +/- 4 years) female volunteers walked at comfortable and fast speed along a linear pathway. The harmonic coefficients of the displacements in the medio-lateral (ML), antero-posterior (AP), and vertical (V) directions were calculated via discrete Fourier transform, and relevant accelerations were computed by analytical double differentiation. The root mean square of the accelerations were used to define three coefficients for quantifying the attenuations of the accelerations from pelvis to head, from pelvis to shoulder, and from shoulder to head.

RESULTS

The coefficients of attenuation were shown to be independent from the walking speed, and hence suitable for group and subject comparison.The acceleration in the AP direction was attenuated by the two groups both from pelvis to shoulder and from shoulder to head. The reduction of the shoulder to head acceleration, however, was less effective in older women, suggesting that the ability to exploit the cervical hinge to attenuate the AP acceleration is challenged in this population. Young women managed to exploit a pelvis to shoulder attenuation strategy also in the ML direction, whereas in the elderly group the head acceleration was even larger than the pelvis acceleration.

CONCLUSION

The control of the head acceleration is fundamental when implementing a locomotor strategy and its loss could be one of the causes for walking instability in elderly women.