The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13-14 years.

INTRODUCTION: Motor competence (MC) is an important factor in the development of health and fitness in adolescence. AIMS: This cross-sectional study aims to explore the distribution of MC across school students aged 13-14 years old and the extent of the relationship of MC to measures of health and fitness across genders. METHODS: A total of 718 participants were tested from three different schools in the UK, 311 girls and 407 boys (aged 13-14 years), pairwise deletion for correlation variables reduced this to 555 (245 girls, 310 boys). Assessments consisted of body mass index, aerobic capacity, anaerobic power, and upper limb and lower limb MC. The distribution of MC and the strength of the relationships between MC and health/fitness measures were explored. RESULTS: Girls performed lower for MC and health/fitness measures compared with boys. Both measures of MC showed a normal distribution and a significant linear relationship of MC to all health and fitness measures for boys, girls and combined genders. A stronger relationship was reported for upper limb MC and aerobic capacity when compared with lower limb MC and aerobic capacity in boys (t=-2.21, degrees of freedom=307, P=0.03, 95% CI -0.253 to -0.011). CONCLUSION: Normally distributed measures of upper and lower limb MC are linearly related to health and fitness measures in adolescents in a UK sample. TRIAL REGISTRATION NUMBER: NCT02517333.

Exploring the Metabolic and Perceptual Correlates of Self-Selected Walking Speed under Constrained and Un-Constrained Conditions.

Mechanisms underpinning self-selected walking speed (SSWS) are poorly understood. The present study investigated the extent to which SSWS is related to metabolism, energy cost, and/or perceptual parameters during both normal and artificially constrained walking. Fourteen participants with no pathology affecting gait were tested under standard conditions. Subjects walked on a motorized treadmill at speeds derived from their SSWS as a continuous protocol. RPE scores (CR10) and expired air to calculate energy cost (J.kg-1.m-1) and carbohydrate (CHO) oxidation rate (J.kg-1.min-1) were collected during minutes 3-4 at each speed. Eight individuals were re-tested under the same conditions within one week with a hip and knee-brace to immobilize their right leg. Deflection in RPE scores (CR10) and CHO oxidation rate (J.kg-1.min-1) were not related to SSWS (five and three people had deflections in the defined range of SSWS in constrained and unconstrained conditions, respectively) (p > 0.05). Constrained walking elicited a higher energy cost (J.kg-1.m-1) and slower SSWS (p < 0.05) versus normal walking. RPE (CR10) was not significantly different between walking conditions or at SSWS (p > 0.05). SSWS did not occur at a minimum energy cost (J.kg-1.m-1) in either condition, however, the size of the minimum energy cost to SSWS disparity was the same (Froude {Fr} = 0.09) in both conditions (p = 0.36). Perceptions of exertion can modify walking patterns and therefore SSWS and metabolism/ energy cost are not directly related. Strategies which minimize perceived exertion may enable faster walking in people with altered gait as our findings indicate they should self-optimize to the same extent under different conditions.

High but not moderate-intensity endurance training increases pain tolerance: a randomised trial.

PURPOSE: To examine the effect of high-intensity interval training (HIIT) compared to volume-matched moderate-intensity continuous training (CONT) on muscle pain tolerance and high-intensity exercise tolerance. METHODS: Twenty healthy adults were randomly assigned (1:1) to either 6 weeks of HIIT [6-8 × 5 min at halfway between lactate threshold and maximal oxygen uptake (50%Δ)] or volume-matched CONT (~60-80 min at 90% lactate threshold) on a cycle ergometer. A tourniquet test to examine muscle pain tolerance and two time to exhaustion (TTE) trials at 50%Δ to examine exercise tolerance were completed pre- and post-training; the post-training TTE trials were completed at the pre-training 50%Δ (same absolute-intensity) and the post-training 50%Δ (same relative-intensity). RESULTS: HIIT and CONT resulted in similar improvements in markers of aerobic fitness (all P ≥ 0.081). HIIT increased TTE at the same absolute- and relative-intensity as pre-training (148 and 43%, respectively) to a greater extent than CONT (38 and -4%, respectively) (both P ≤ 0.019). HIIT increased pain tolerance (41%, P < 0.001), whereas CONT had no effect (-3%, P = 0.720). Changes in pain tolerance demonstrated positive relationships with changes in TTE at the same absolute- (r = 0.44, P = 0.027) and relative-intensity (r = 0.51, P = 0.011) as pre-training. CONCLUSION: The repeated exposure to a high-intensity training stimulus increases muscle pain tolerance, which is independent of the improvements in aerobic fitness induced by endurance training, and may contribute to the increase in high-intensity exercise tolerance following HIIT.

Acute recovery from exercise in people with multiple sclerosis: an exploratory study on the effect of exercise intensities.

Purpose A better understanding of how people with multiple sclerosis (pwMS) recover from exercise may help inform interventions. Methods We explored physiological and perceptual responses following exercise of different intensities, using a crossover exposure-response design, in 14 adults with multiple sclerosis (MS) and 9 controls. A cycling exercise test determined maximum capacity (Wpeak). Participants then performed 20-min exercise sessions relative to Wpeak (random order separated by 7 days): (1) 45% and (2) 60% continuous cycling and (3) 90% intermittent cycling (30 s cycling, 30 s rest). During a 45-min recovery period, tympanic temperature (Temp°C), exertion in breathing (RPEbr) and legs (RPEleg), and cortical excitability (MEParea) were measured. Results Eleven pwMS and eight controls completed the study. Controls performed better on the exercise test (p < 0.05), thus more absolute work during subsequent sessions. PwMS took longer to recover RPEleg with recovery time increasing with intensity (45%-6 min; 60%-15 min; 90%-35 min) and correlating with Temp°C. MEParea was significantly depressed in both groups at 45% and 60% (p < 0.001), in the MS group this also correlated with RPEleg. Conclusions Feelings of leg exertion may persist after exercise in some pwMS, especially at high intensities. This may relate to body temperature and, after continuous exercise, cortical excitability. These results support considering the recovery period post exercise and provide an insight into potential correlates of post-exercise fatigue. Implications for Rehabilitation A better understanding of how pwMS recover following exercise may help inform exercise prescription a long side fatigue management. This study showed that, in pwMS, the time taken to recover from feelings of leg fatigue increased with the intensity of the exercise session rather that total work performed and was related to increase in body temperature. The results of this relatively small study support the need to consider a recovery period after exercise and provide an insight into potential physiological correlates.

Reliability of single and paired-pulse transcranial magnetic stimulation in the vastus lateralis muscle.

INTRODUCTION: Transcranial magnetic stimulation (TMS) is an important tool to examine neurological pathologies, movement disorders, and central nervous system responses to exercise, fatigue, and training. The reliability has not been examined in a functional locomotor knee extensor muscle. METHODS: Within- (n = 10) and between-day (n = 16) reliability of single and paired-paired pulse TMS was examined from the active vastus lateralis. RESULTS: Motor evoked potential amplitude and cortical silent period duration showed good within- and between-day reliability (intraclass correlation coefficient [ICC] ≥ 0.82). Short- and long-interval intracortical inhibition (SICI and LICI, respectively) demonstrated good within-day reliability (ICC ≥ 0.84). SICI had moderate to good between-day reliability (ICC ≥ 0.67), but LICI was not repeatable (ICC = 0.47). Intracortical facilitation showed moderate to good within-day reliability (ICC ≥ 0.73) but poor to moderate reliability between days (ICC ≥ 0.51). CONCLUSIONS: TMS can reliably assess cortical function in a knee extensor muscle. This may be useful to examine neurological disorders that affect locomotion.

Motor impairment and its relationship to fitness in children.

OBJECTIVES: The aim of this work was to explore the physiological and perceptual limits to exercise in children with varying degrees of motor impairment, and the relationships to measures of health. DESIGN AND METHODS: In a group comparison design, 35 boys aged 12-15 years completed the Movement ABC test for the assessment of motor impairment, followed by an incremental cycle ergometer test to exhaustion for the assessment of maximal oxygen uptake (VO2peak), respiratory exchange ratio (RER), heart rate (HR) and rating of perceived exertion (RPE). Ten participants classified as having either high or no motor impairment also performed a maximal voluntary isometric contraction (MVIC) for the assessment of lower limb extensor strength. RESULTS: 18 boys were classified as having high motor impairment. There was a significant difference in peak (34.9 vs 48.5 mL kg/min), workload (12.5 vs 10.0 mL W), maximal HR (176 vs 188 bpm), maximal oxygen pulse (12.1 vs 15.9 mL beat) and MVIC (5.7 vs 9.1 Nm kg) between the high and non-motor impaired participants, respectively, (p<0.05). There was no significant difference in the RER or RPE between groups. CONCLUSIONS: When performing cycling ergometry, perceived exertion was not a limiting factor in children with high motor impairment. The lower maximal HR, coupled with reduced movement efficiency and muscle strength reported in this group, suggests that exercise is limited by impairment at the muscular level. This finding was supported by high RER values despite low maximal HR values attained at exercise cessation and reduced maximal strength. Perception of effort is not heightened in children with high motor impairment and future-exercise interventions should be focused on improving muscular condition in these participants to enable them to be better prepared to engage in physical activity for health.

Insights into gait disorders: walking variability using phase plot analysis, Parkinson's disease.

Gait variability may have greater utility than spatio-temporal parameters and can, be an indication for risk of falling in people with Parkinson's disease (PD). Current methods rely on prolonged data collection in order to obtain large datasets which may be demanding to obtain. We set out to explore a phase plot variability analysis to differentiate typically developed adults (TDAs) from PD obtained from two 10 m walks. Fourteen people with PD and good mobility (Rivermead Mobility Index≥8) and ten aged matched TDA were recruited and walked over 10-m at self-selected walking speed. An inertial measurement unit was placed over the projected centre of mass (CoM) sampling at 100 Hz. Vertical CoM excursion was derived to determine modelled spatiotemporal data after which the phase plot analysis was applied producing a cloud of datapoints. SDA described the spread and SDB the width of the cloud with ß the angular vector of the data points. The ratio (∀) was defined as SDA: SDB. Cadence (p=.342) and stride length (p=.615) did not show a significance between TDA and PD. A difference was found for walking speed (p=.041). Furthermore a significant difference was found for ß (p=.010), SDA (p=.004) other than SDB (p=.385) or ratio ∀ (p=.830). Two sequential 10-m walks showed no difference in PD for cadence (p=.193), stride length (p=.683), walking speed (p=.684) and ß (p=.194), SDA (p=.051), SDB (p=.145) or ∀ (p=.226). The proposed phase plot analysis, performed on CoM motion could be used to reliably differentiate PD from TDA over a 10-m walk.

Validity and inter-rater reliability of inertial gait measurements in Parkinson's disease: a pilot study.

Walking models driven by centre of mass (CoM) data obtained from inertial measurement units (IMU) or optical motion capture systems (OMCS) can be used to objectively measure gait. However current models have only been validated within typical developed adults (TDA). The purpose of this study was to compare the projected CoM movement within Parkinson's disease (PD) measured by an IMU with data collected from an OMCS after which spatio-temporal gait measures were derived using an inverted pendulum model. The inter-rater reliability of spatio-temporal parameters was explored between expert researchers and clinicians using the IMU processed data. Participants walked 10 m with an IMU attached over their centre of mass which was simultaneously recorded by an OMCS. Data was collected on two occasions, each by an expert researcher and clinician. Ten people with PD showed no difference (p=0.13) for vertical, translatory acceleration, velocity and relative position of the projected centre of mass between IMU and OMCS data. Furthermore no difference (p=0.18) was found for the derived step time, stride length and walking speed for people with PD. Measurements of step time (p=0.299), stride length (p=0.883) and walking speed (p=0.751) did not differ between experts and clinicians. There was good inter-rater reliability for these parameters (ICC3.1=0.979, ICC3.1=0.958 and ICC3.1=0.978, respectively). The findings are encouraging and support the use of IMUs by clinicians to measure CoM movement in people with PD.

Alterations in peripheral muscle contractile characteristics following high and low intensity bouts of exercise.

The aim of this study was to monitor muscle contractile performance in vivo, using an electrical stimulation protocol, immediately following an acute high and low intensity exercise session conducted at the same average intensity performed on a cycle ergometer. Eighteen healthy males (25.1 ± 4.5 years, 81.6 ± 9.8 kg, 1.83 ± 0.06 m; mean ± SD) participated in the study. On two occasions, separated by 1 week, subjects completed a high and low intensity exercise session in a random order on a cycle ergometer, performing equal total work in each. At the end of each test, a muscle performance test using electrical stimulation was performed within 120 s. Post-exercise muscle data were compared to the subjects' rested muscle. We found a reduction in muscle contractile performance following both high and low intensity exercise protocols but a greater reduction in maximal voluntary contraction (MVC) (P < 0.01), rate of torque development (RTD) (P < 0.001), rate of relaxation (RR(½)), (P < 0.001) the 60 s slope of the fatigue protocol (P < 0.01) and torque frequency response (P < 0.05) following the high intensity bout. Importantly muscle performance remained reduced 1 h following high intensity exercise but was recovered following low intensity exercise. Muscle function was significantly reduced following higher intensity intermittent exercise in comparison to lower intensity exercise even when the average overall intensity was the same. This study is the first to demonstrate the sensitivity of muscle contractile characteristics to different exercise intensities and the impact of higher intensity bursts on muscle performance.

Assessment of spatio-temporal gait parameters using inertial measurement units in neurological populations.

Laboratory based gait analysis techniques are expensive, time consuming and require technical expertise. Inertial measurement units can directly measure temporal parameters and in combination with gait models may provide a solution to obtain spatial gait measurements within daily clinical assessments. However it is not known if a model and standard correction factor determined by Zijlstra and Hof [8] to estimate step and stride length parameters in typically developed adults (TDA) can be accurately used in neurologically impaired gaits. This research estimated the stride length over two 10 m walks at self selected walking speed in people with neurological conditions, using a previously established model and correction factor for TDA. The relation of the correction factor to walking speed was explored. We recruited TDA (n=10) and participants with Parkinson's disease (PD; n=24), muscular dystrophy (MD; n=13), motor neuron disease (MND; n=7) and stroke survivors (n=18) for the study who twice walked 10 m at a self-selected pace. Stride length correction factors, for TDA (1.25±0.01), PD (1.25±0.03), and MD (1.21±0.08) (p=0.833 and p=0.242) were the same as previously reported in TDA (Zijlstra and Hof [8]). Correction factors for stroke (1.17±0.42) and MND (1.10±0.08) were different (p<0.01 and p=0.028 respectively). However there was a high level of variability for correction factors within groups, which did not relate to walking speed. Our findings support that correction factors should be determined for each individual to estimate average step/stride length in patients suffering from a neurological condition.

Cognitive context determines dorsal premotor cortical activity during hand movement in patients after stroke.

BACKGROUND AND PURPOSE: Stroke patients often have difficulties in simultaneously performing a motor and cognitive task. Functional imaging studies have shown that movement of an affected hand after stroke is associated with increased activity in multiple cortical areas, particularly in the contralesional hemisphere. We hypothesized patients for whom executing simple movements demands greater selective attention will show greater brain activity during movement. METHODS: Eight chronic stroke patients performed a behavioral interference test using a visuo-motor tracking with and without a simultaneous cognitive task. The magnitude of behavioral task decrement under cognitive motor interference (CMI) conditions was calculated for each subject. Functional MRI was used to assess brain activity in the same patients during performance of a visuo-motor tracking task alone; correlations between CMI score and movement-related brain activation were then explored. RESULTS: Movement-related activation in the dorsal precentral gyrus of the contralesional hemisphere correlated strongly and positively with CMI score (r(2) at peak voxel=0.92; P<0.05). Similar but weaker relationships were observed in the ventral precentral and middle frontal gyrus. There was no independent relationship between hand motor impairment and CMI. CONCLUSIONS: Results suggest that variations in the degree to which a cognitive task interferes with performance of a concurrent motor task explains a substantial proportion of the variations in movement-related brain activity in patients after stroke. The results emphasize the importance of considering cognitive context when interpreting brain activity patterns and provide a rationale for further evaluation of integrated cognitive and movement interventions for rehabilitation in stroke.

Hydration and independence in activities of daily living in people with multiple sclerosis: a pilot investigation.

PURPOSE: Bladder dysfunction and disability may cause people with multiple sclerosis (pwMS) to limit fluid intake. However, hydration is rarely considered in the multiple sclerosis literature. We investigated the hydration status of people with pwMS and its association with independence in activities of daily living. METHODS: Twenty-six (six men) pwMS over 18 years old and able to walk with or without an aid took part in the study. Hydration status was measured via urine osmolality, with adequate hydration defined as an osmolality ≤500 (mOsm kg(-1)). Independence in daily activities was measured using the Barthel index. RESULTS: Mean urine osmolality was 470 ±â€Š209 mOsm kg(-1) and indicated 11 (42%) participants were not adequately hydrated. Independence in daily activities could partly explain hydration status (R(2) = 0.209, p < 0.05). Additionally there was a trend for men to be less well hydrated than women. CONCLUSIONS: The results indicate that some pwMS were not adequately hydrated and that this could be partly explained by disability. Implications of reducing and maintaining fluid levels on function and quality of life in relation to bladder dysfunction and disability in pwMS should be investigated.

Cognitive motor interference while walking: a systematic review and meta-analysis.

Dual-task methodology has been increasingly used to assess cognitive motor interference while walking. However, whether the observed dual-task-related gait changes are systematically related to methodological variations remains unclear and researchers still lack knowledge of what cognitive task to use in different groups for clinical purposes or for research. We systematically reviewed experimental studies that measured gait performance with and without performing concurrent cognitive task. Our results suggest that cognitive tasks that involve internal interfering factors seem to disturb gait performance more than those involving external interfering factors. Meta-analysis results show that the overall effect of different cognitive tasks was prominent in gait speed. In healthy participants, meta-regression analysis suggests strong associations between age and speed reduction under dual-task conditions and between the level of cognitive state and speed reduction under dual-task conditions. Standardizing research methodologies, as well as improving their ecological validity, enables better understanding of dual-task-related gait changes in different populations and improves, in turn, our understanding of neural mechanisms and gait control in general in content.

Muscle contractile characteristics: relationship to high-intensity exercise.

We investigated the relationship between muscle contractile characteristics, collected using percutaneous electrical stimulation, and high-intensity exercise performance. Seventeen participants performed a muscle performance test for the calculation of rate of torque development (RTD), rate of relaxation (RR(1/2)), rate of fatigue and fatigue resistance. On a second visit the participants completed a Wingate cycle ergometer test with peak power, mean power, fatigue index and fatigue rate calculated. The muscle fatigue index related significantly to the WAnT fatigue index and fatigue rate (p < 0.01). The change in rate of torque development (%DeltaRTD) was also related significantly to the fatigue rate (W/s) during the WAnT. Subjects displaying the greatest reduction in RTD had the greatest fatigue rate during the WAnT and greater fatigue during the electrical stimulation protocol. There were no significant relationships between peak (r 0.36; p > 0.01) or mean power (r -0.11, p > 0.01) with any of the muscle performance measures. These findings demonstrate that muscle contractile characteristics, elicited during standardised in vivo electrical stimulation, relate to performance during a Wingate anaerobic test. They suggest that muscle contraction characteristics play an important role in high-intensity exercise performance and indicate that electrical stimulation protocols can be a useful additional tool to explore muscle contraction characteristics in relation to exercise performance and trainability.

Gait adaptations to simultaneous cognitive and mechanical constraints.

Previous studies have shown that walking is not a purely automatic motor task but places demands on sensory and cognitive systems. We set out to investigate whether complex walking tasks, as when walking down a steeper gradient while performing a concurrent cognitive task, would demand gait adaptation beyond those required for walking under low-challenge conditions. Thirteen healthy young individuals walked at their self-selected speed on a treadmill at different inclinations (0, -5 and -10%). Gait spatio-temporal measures, pelvis angular excursion, and sacral centre of mass (CoM) motion were acquired while walking or while walking and performing a mental tracking task. Repeated-measures ANOVAs revealed that decreasing treadmill inclination from 0 to -10% resulted in significant decreased walking speed (P < 0.001), decreased stride length (P < 0.001), increased pelvis tilt (P = 0.006) and obliquity variability (P = 0.05), decreased pelvis rotation (P = 0.02), and increased anterio-posterior (A-P) CoM displacement (P = 0.015). Compared to walking alone, walking under dual-task condition resulted in increased step width (P < 0.001), and increased medio-lateral (M-L) CoM displacement (P = 0.039) regardless of inclination grade, while sagittal plane dynamics did not change. Findings suggest that gait adapts differently to cognitive and mechanical constraints; the cognitive system is more actively involved in controlling frontal than sagittal plane gait dynamics, while the reverse is true for the mechanical system. Finally, these findings suggest that gait adaptations maintain the ability to perform concurrent tasks while treadmill walking in healthy young adults.

Fast walking under cognitive-motor interference conditions in chronic stroke.

Gait in stroke patients is often characterised by slower speeds, which may be exacerbated by situations that combine gait with a cognitive task, leading to difficulties with everyday activities. Interaction between cognitive task performance and gait speed may differ according to walking intensity. This study examines the effects of two cognitive tasks on gait at preferred walking pace, and at a faster pace, using dual-task methodology. 21 chronic stroke patients and 10 age-matched control subjects performed 2 single motor tasks (walking at preferred and at fast pace around a walkway), and two cognitive tasks (serial subtractions of 3s and a visual-spatial decision task) under single- and dual-task conditions (cognitive-motor interference) in a randomised order. Cognitive task score and gait speed were measured. The healthy control group showed no effects of CMI. The stroke group decreased their walking speed whilst concurrently performing serial 3s during both preferred and fast walking trials and made more mistakes in the visuo-spatial task during fast walking. There was no effect of walking on the serial 3 performance. The findings show that in stroke patients, during walking whilst concurrently counting backwards in 3s the cognitive task appeared to take priority over maintenance of walking speed. During fast walking whilst concurrently performing a visuo-spatial imagery task, they appeared to favour walking. This may indicate that people spontaneously favour one activity over the other, which has implications for gait rehabilitation.

IMU: inertial sensing of vertical CoM movement.

The purpose of this study was to use a quaternion rotation matrix in combination with an integration approach to transform translatory accelerations of the centre of mass (CoM) from an inertial measurement unit (IMU) during walking, from the object system onto the global frame. Second, this paper utilises double integration to determine the relative change in position of the CoM from the vertical acceleration data. Five participants were tested in which an IMU, consisting of accelerometers, gyroscopes and magnetometers was attached on the lower spine estimated centre of mass. Participants were asked to walk three times through a calibrated volume at their self-selected walking speed. Synchronized data were collected by an IMU and an optical motion capture system (OMCS); both measured at 100 Hz. Accelerations of the IMU were transposed onto the global frame using a quaternion rotation matrix. Translatory acceleration, speed and relative change in position from the IMU were compared with the derived data from the OMCS. Peak acceleration in vertical axis showed no significant difference (p> or =0.05). Difference between peak and trough speed showed significant difference (p<0.05) but relative peak-trough position between the IMU and OMCS did not show any significant difference (p> or =0.05). These results indicate that quaternions, in combination with Simpsons rule integration, can be used in transforming translatory acceleration from the object frame to the global frame and therefore obtain relative change in position, thus offering a solution for using accelerometers in accurate global frame kinematic gait analyses.

Pedometer step counts in individuals with neurological conditions.

OBJECTIVE: To examine the accuracy of measuring step counts using a pedometer in participants with neurological conditions and healthy volunteers in relation to a manual step count tally. SETTING: Oxford Centre for Enablement, Nuffield Orthopaedic Centre NHS Trust, Oxford, UK. SUBJECTS: Healthy adults (n = 13, age: mean 29, SD = 12) and adults with neurological conditions (n=20 stroke, n=16 multiple sclerosis, n=5 muscular dystrophy, n=1 spinal cord injury, n=1 traumatic brain injury; age: mean 54, SD=13). MAIN MEASURES: Individuals walked for 2 minutes at self-selected walking speeds (SSWS) wearing a pedometer. Healthy individuals were then asked to walk at slow walking speeds (SWS). Step counts were recorded manually and using a pedometer. RESULTS: In healthy individuals there was no difference between manually measured and pedometer counts during walking (P>0.05). In adults with neurological conditions the pedometers undercounted (P = 0.003); bias (random error): 27 (111); percentage variability 30% and intraclass correlation coefficient (ICC) 0.66. In neurological adults, from regression analysis the relationship between error and walking speed was cubic, with walking speed accounting for 29% of pedometer error. Healthy individuals showed greater variability and undercounting at SWS bias (random error): 10 (31), percentage variability 8% and ICC 0.73, compared with SSWS bias (random error): -3 (13), percentage variability 3% and ICC 0.84. CONCLUSIONS: Pedometers may undercount when used for people with neurological conditions. There may be variability in pedometer accuracy but this was not strongly related to walking speed. The suitability of pedometer use for exercise monitoring should be individually determined.

Relationships between muscle fatigue characteristics and markers of endurance performance.

The aim of this study was to examine the relationship of a range of in-vivo whole muscle characteristics to determinants of endurance performance. Eleven healthy males completed a cycle ergometer step test to exhaustion for the determination of the lactate threshold, gross mechanical efficiency, peak power and VO2max. On two separate occasions, contractile and fatigue characteristics of the quadriceps femoris were collected using a specially designed isometric strength-testing chair. Muscle fatigue was then assessed by stimulating the muscle for 3 minutes. Force, rate of force development and rates of relaxation were calculated at the beginning and end of the 3 minute protocol and examined for reliability and in relation to lactate threshold, VO2max, gross mechanical efficiency and peak power. Muscle characteristics, rate of force development and relaxation rate were demonstrated to be reliable measures. Force drop off over the 3 minutes (fatigue index) was related to lactate threshold (r = -0.72 p » 0.01) but not to VO2max. The rate of force development related to the peak power at the end of the cycle ergometer test (r = -0.75 p » 0.01). Rates of relaxation did not relate to any of the performance markers. We found in-vivo whole muscle characteristics, such as the fatigue index and rate of force development, relate to specific markers of peripheral, but not to central, fitness components. Our investigation suggests that muscle characteristics assessed in this way is reliable and could be feasibly utilised to further our understanding of the peripheral factors underpinning performance. Key pointsParticipants with a high lactate threshold displayed greater fatigue resistance in the electrical stimulation test.Muscle performance characteristics relate to specific components of endurance performance.The electrical stimulation protocol could be a useful technique, alongside other established measures, when constructing a physiological profile of a participant.

Anomalous centre of mass energy fluctuations during treadmill walking in healthy individuals.

Motorised treadmills are used to research and rehabilitate gait despite conflicting evidence that treadmill ambulation is equivalent to ground walking. It has been suggested that no mechanical differences should exist between these environments but there is little evidence to support this. During ground walking, the whole body centre of mass (COM) acts like an inverted pendulum recovering energy, thereby reducing the effort of locomotion. The energy recovery has a relationship with speed whereby maximum recovery occurs at intermediate speeds. In order to determine the relationship between energy recovery and speed during treadmill walking, we investigated estimated COM displacement in nine healthy individuals each walking on a treadmill at seven different speeds. In addition, we measured oxygen cost to determine the effort of walking. Our participants formed two distinct groups, those with normal COM energy recovery (N%R) that was similar to ground walking, and those with low COM energy recovery (L%R) that was different from typical ground walking. The low energy recovery in the L%R group was attributed to in-phase potential and kinetic energy fluctuations. Despite the low energy recovery values both groups produced the expected 'U'-shaped oxygen cost speed curve with no significant difference between groups (p<0.05), however, only N%R produced a significant relationship between energy recovery and oxygen cost (p<0.05). Although a useful tool, walking on a treadmill may not be a true representation of ground walking and therefore not the most effective way to research or rehabilitate gait.