Effect of a high intensity quadriceps fatigue protocol on knee joint mechanics and muscle activation during gait in young adults

Lower Limb Muscle Fatigue Alters Spatiotemporal Gait Parameters and Turning Difficulty Characteristics in Parkinson's Disease

OBJECTIVE

To determine the effects of lower limb muscle fatigue on spatiotemporal gait parameters and turning difficulty characteristics during the extended Timed Up and Go (extended TUG) test in individuals with different severity stages of Parkinson's disease (PD).

METHODS

Forty individuals with PD, classified as Hoehn and Yahr (H&Y) stages 2 and 3 participated in this pre- and post-experimental study design. The participants performed a continuous sit-to-stand task from a chair based on 30 cycles/min set-up to induce lower limb muscle fatigue. They performed extended TUG test immediately before and after completing the fatigue protocol. Spatiotemporal gait parameters and turning difficulty characteristics were recorded using two GoPro® Hero 4 Silver cameras. Data were subjected to a repeated-measure ANOVA.

RESULTS

Individuals with PD experience significant changes in spatiotemporal gait parameters, specifically stride velocity and length, under conditions of lower limb muscle fatigue (p=0.001). These changes were more pronounced in individuals with PD in the H&Y stage 3 group. Additionally, both PD groups exhibited difficulty with turning, requiring more than five steps to complete a 180° turn and taking more than 3 seconds to accomplish it.

CONCLUSION

These findings highlight the impact of muscle fatigue on gait performance in PD and suggest that individuals in later stages of the disease may be particularly affected. Further research is needed to explore interventions that can mitigate these gait impairments and improve mobility in individuals with PD.

Challenges and advances in the use of wearable sensors for lower extremity biomechanics

The use of wearable sensors for the collection of lower extremity biomechanical data is increasing in popularity, in part due to the ease of collecting data and the ability to capture movement outside of traditional biomechanics laboratories. Consequently, an increasing number of researchers are facing the challenges that come with utilizing the data captured by wearable sensors. These challenges include identifying/calculating meaningful measures from unfamiliar data types (measures of acceleration and angular velocity instead of positions and joint angles), defining sensor-to-segment alignments for calculating traditional biomechanics metrics, using reduced sensor sets and machine learning to predict unmeasured signals, making decisions about when and how to make algorithms freely available, and developing or replicating methods to perform basic processing tasks such as recognizing activities of interest or identifying gait events. In this perspective article, we present our own approaches to common challenges in lower extremity biomechanics research using wearable sensors and share our perspectives on approaching several of these challenges. We present these perspectives with examples that come mostly from gait research, but many of the concepts also apply to other contexts where researchers may use wearable sensors. Our goal is to introduce common challenges to new users of wearable sensors, and to promote dialogue amongst experienced users towards best practices.

Effect of fatigue on kinematics, kinetics and muscle activities of lower limbs during gait

Muscle fatigue, as a serious social problem, affects the performance of daily living activities, especially for workers. Decrease of movement control ability caused by muscle fatigue is one of the risk and intrinsic factors for occupational accidents, such as slips, trips, falls, etc. In order to reduce the accident rate and optimize the existing prevention measures, it is necessary to investigate the effect of fatigue on kinematics, kinetics, and muscle activities of human body. In this paper, 26 healthy participants were recruited. The kinematics and kinetics analysis of lower limb joints, and surface electromyograms (sEMG) time-domain and frequency-domain analysis of lower limb periarticular muscles were utilized to investigate the effects of muscle fatigue. The results showed that the fatigue reduced the range-of-motion (RoM) of the lower limb joints. Smaller plantarflexion, knee flexion and hip flexion angles, and greater dorsiflexion angles were observed after fatigue. For the joint moment, the fatigue did not alter the joint moments except for the smaller knee flexion moment. For the joint power, the fatigue decreased the generation power of ankle, knee and hip joint and the absorption power of ankle and knee joints, whereas increased the absorption power of hip joint. Besides, the fatigue increased the normalized integrated sEMG (iEMG) and root-mean-square (RMS) of sEMG, and shifted the median frequency (MF) and mean power frequency (MPF) of sEMG toward lower frequencies. The results from the present study concluded that the muscle fatigue changed the kinematics, kinetics and muscle activities of lower limbs during gait, and then could increase the risk rate of occupational accidents.

Experimental study protocol of the project "MOtor function and VItamin D: Toolkit for motor performance and risk Assessment (MOVIDA)"

Musculoskeletal injuries, a public health priority also in the military context, are ascribed to several risk factors, including: increased reaction forces; low/reduced muscle strength, endurance, body mass, Vitamin D level, and bone density; inadequate lifestyles and environment. The MOVIDA Project-funded by the Italian Ministry of Defence-aims at developing a transportable toolkit (assessment instrumentation, assessment protocols and reference/risk thresholds) which integrates motor function assessment with biological, environmental and behavioural factors to help characterizing the risk of stress fracture, stress injury or muscle fatigue due to mechanical overload. The MOVIDA study has been designed following the STROBE guidelines for observational cross-sectional studies addressing healthy adults, both militaries and civilians, with varying levels of physical fitness (sedentary people, recreational athletes, and competitive athletes). The protocol of the study has been designed and validated and is hereby reported. It allows to collect and analyse anamnestic, diagnostic and lifestyle-related data, environmental parameters, and functional parameters measured through portable and wearable instrumentation during adapted 6 minutes walking test. The t-test, one and two-way ANOVA with post-hoc corrections, and ANCOVA tests will be used to investigate relevant differences among the groups with respect to biomechanical parameters; non-parametric statistics will be rather used for non-normal continuous variables and for quantitative discrete variables. Generalized linear models will be used to account for risk and confounding factors.

Overuse-Related Injuries of the Musculoskeletal System: Systematic Review and Quantitative Synthesis of Injuries, Locations, Risk Factors and Assessment Techniques

Overuse-related musculoskeletal injuries mostly affect athletes, especially if involved in preseason conditioning, and military populations; they may also occur, however, when pathological or biological conditions render the musculoskeletal system inadequate to cope with a mechanical load, even if moderate. Within the MOVIDA (Motor function and Vitamin D: toolkit for risk Assessment and prediction) Project, funded by the Italian Ministry of Defence, a systematic review of the literature was conducted to support the development of a transportable toolkit (instrumentation, protocols and reference/risk thresholds) to help characterize the risk of overuse-related musculoskeletal injury. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) approach was used to analyze Review papers indexed in PubMed and published in the period 2010 to 2020. The search focused on stress (overuse) fracture or injuries, and muscle fatigue in the lower limbs in association with functional (biomechanical) or biological biomarkers. A total of 225 Review papers were retrieved: 115 were found eligible for full text analysis and led to another 141 research papers derived from a second-level search. A total of 183 papers were finally chosen for analysis: 74 were classified as introductory to the topics, 109 were analyzed in depth. Qualitative and, wherever possible, quantitative syntheses were carried out with respect to the literature review process and quality, injury epidemiology (type and location of injuries, and investigated populations), risk factors, assessment techniques and assessment protocols.

Effects of prolonged walking with body borne load on knee adduction biomechanics

BACKGROUND

Soldiers that suffer a service-related knee musculoskeletal injury routinely develop joint osteoarthritis. Knee osteoarthritis is a substantial and costly problem among soldiers, yet it is unknown how body borne load and duration of walking impact knee adduction biomechanics linked to progression and severity of osteoarthritis.

RESEARCH QUESTION

This study determined the adaptations in magnitude and variability of knee adduction joint angle (KAA) and moment (KAM) during prolonged walking with body borne load.

METHODS

Thirteen recreationally active participants had knee biomechanics quantified while walking over-ground for 60-min at 1.3 m/s with three body borne loads (0, 15, and 30 kg). Magnitude and variability of KAA and KAM measures were quantified and submitted to a RM ANOVA to test the main effect and interactions between load (0, 15 and 30 kg) and time (0, 15, 30, 45 and 60 min).

RESULTS

Body borne load increased peak KAM (p < 0.001), whereas time increased peak and range of KAA (both: p < 0.001). Specifically, peak KAM increased with each addition of body borne load (all: p < 0.025), and peak and range of KAA increased after 30 min of walking (both: p < 0.040). Neither body borne load, nor time had a significant effect on KAA or KAM variability (both: p > 0.05).

SIGNIFICANCE

Prolonged walking with heavy body borne load increased knee adduction biomechanics related to osteoarthritis. Adding heavy body borne load increased in peak KAM whereas duration of walking increased KAA, knee biomechanics that may increase loading of the medial knee joint compartment and risk of OA at the joint.

Electromyographic traces of motor unit synchronization of fatigued lower limb muscles during gait

BACKGROUND

The study of the signal in the frequency domain has shown to be a good tool to identify muscular fatigue. Previous research has shown that the low frequency band and 40 Hz frequency band increase their relative intensity with the onset of fatigue. These findings were obtained in rectus femoris, but the behaviours of other muscles of the lower limb are unknown. In this article we explored the changes in the low frequency and 40 Hz frequency band of lower limb muscles with respect to fatigue.

METHODS

Thirty healthy subjects were recruited to analyse the electromyography (EMG) of biceps femoris, tibialis anterior and gastrocnemius medialis and lateralis of both legs during gait. Four two-minutes walks at a self-selected speed were recorded, the first two walks with a normal muscular function and the last two walks after a fatigue protocol. All the signals were decomposed using wavelet transformations. The signals were normalized in time and spectral intensities normalized to the sum of intensities in the frequency domain. Two frequency bands were studied in each walk: the 40-Hz (34-53 Hz) and the low frequency (< 25 Hz) bands. A ratio of the spectral intensities of those frequency bands at each walk was obtained by dividing the 40-Hz frequency band spectral intensity by the low frequency band spectral intensity. Statistical parametric mapping techniques were used to compare the ratios of the prefatigue walks against the postfatigue walks.

RESULTS

The results of the Statistical Non-Parametric Mapping (SnPM) analysis of all muscles depict a higher relative spectral intensity in the low frequency band in the comparison of fatigue versus prefatigue recordings except for the right gastrocnemius lateralis. The critical thresholds F* were exceeded by multiple suprathreshold clusters with p values <0.05, showing that the low frequency band increased its relative spectral intensity in the case of fatigue.

CONCLUSION

The obtained results suggest that the low frequency band increases its relative spectral intensity in all the studied muscles when fatigue onsets. This increase in relative spectral intensity may be linked to an increase in motor unit synchronization promoted by the central nervous system to ensure good motor control.

Gender differences in the knee joint loadings during gait

BACKGROUND

The differences in anatomical structure between men and women are widely known. Unfortunately, the influence of gender on the biomechanics of a healthy knee joint during gait is still poorly understood.

RESEARCH QUESTION

The aim of the presented study was to determine loads acting in the knee joint during gait, based on the observation of a large group of healthy young adults, in particular to determine the influence of gender on values of forces and moments and their time characteristics during gait cycle.

METHODS

Time-spatial gait parameters and ground reaction force were registered for 86 persons (43 females and 43 males) using a motion capture system and force plates. The numerical simulation with the AnyBody system was used to estimate loadings acting in the knee joint. Differences between women and men were tested using the unpaired Student's t-test with a Bonferroni correction.

RESULTS

The maximum values of loadings acting in the knee joint were: 411.1 %BW (body weight) for resultant force, 390.6 %BW for proximo-distal force, 110.8 %BW for antero-posterior force, 77.0 %BW for medio-lateral force, 2.63 %BWh (body weight times height) for flexion/extension moment, 0.97 %BWh for internal/external rotation moment and 5.7 %BWh for abduction/adduction moment. In general, the normalised forces were greater in the male group, while the normalised external moments acting on the knee were greater in the female group. Local extrema of forces during the stance phase were observed earlier for women.

SIGNIFICANCE

Knowledge about gender differences in loadings acting in the knee joint can be of great importance in the case of detecting the early stages of gait abnormalities and treatment planning.

Effects of Knee Savers on the quadriceps muscle activation across deep knee bending postures

Workers who kneel or squat frequently are at a high risk of developing knee pathologies. Knee Savers^® are wedge-shaped pads, worn on the lower calf by baseball catchers that aim to reduce this risk. This study examined how Knee Savers^® change the bilateral quadriceps muscle activity during dorsiflexed kneeling, and heels-up and flat-foot squatting. For twenty participants, integrated and peak electromyography (EMG) during descent and ascent phases, mean EMG during a 10-s static phase, and participants' subjective perception of muscle fatigue were compared between equipment conditions (with (W) and without (WO) Knee Savers^®). Knee Savers^® did not significantly reduce integrated or peak EMG during transitions into and out of the postures; however, they significantly reduced (p < .03) mean EMG in five of six muscles during the static phase. These findings indicate potential for Knee Savers^® to reduce cumulative muscular effort and fatigue in applications where prolonged static kneeling or squatting are required.

Minimal effects of age and prolonged physical and mental exercise on healthy adults' gait

BACKGROUND

Gait adaptability in old age can be examined by responses to various perturbations. Fatigability due to mental or muscle exercises can perturb internal cognitive and muscle resources, necessitating adaptations in gait.

RESEARCH QUESTION

What are the effects of age and mental and muscle fatigability on stride outcomes and gait variability?

METHODS

Twelve older (66-75yrs) and twelve young (20-25 yrs) adults walked at 1.2 m/s before and after two fatigue conditions in two separate sessions. Fatigue conditions were induced by repetitive sit-to-stand task (RSTS) and by 30-min of mental tasks and randomized between days (about a week apart). We calculated the average and coefficient of variation of stride length, width, single support, swing time and cadence, and the detrended fluctuations analysis (DFA) based on 120 strides time intervals. We also calculated multi-scale sample entropy (MSE) and the maximal Lyapunov exponent (λmax) of mediolateral (ML) and anteroposterior (AP) of the Center of Pressure (CoP) trajectories.

RESULTS

In both age groups, RSTS modestly affected stride length, single support time, cadence, and CV of stride length (p ≤ 0.05), while the mental task did not affect gait. After fatigability, λmax - ML increased (p ≤ 0.05), independent of fatigue condition. All observed effects were small (η²: 0.001 to 0.02).

SIGNIFICANCE

Muscle and mental fatigability had minimal effects on gait in young and healthy older adults possibly because treadmill walking makes gait uniform. It is still possible that age-dependent muscle activation underlies the uniform gait on the treadmill. Age- and fatigability effects might be more overt during real life compared with treadmill walking, creating a more effective model for examining gait and age adaptability to fatigability perturbations.

Effects of anti-pronation shoes on lower limb kinematics and kinetics in female runners with pronated feet: The role of physical fatigue

Physical fatigue and pronated feet constitute two risk factors for running-related lower limb injuries. Accordingly, different running shoe companies designed anti-pronation shoes with medial support to limit over pronation in runners. However, there is little evidence on the effectiveness and clinical relevance of anti-pronation shoes. This study examined lower limb kinematics and kinetics in young female runners with pronated feet during running with anti-pronation versus regular (neutral) running shoes in unfatigued and fatigued condition. Twenty-six female runners aged 24.1±5.6 years with pronated feet volunteered to participate in this study. Kinetic (3D Kistler force plate) and kinematic analyses (Vicon motion analysis system) were conducted to record participants’ ground reaction forces and joint kinematics when running with anti-pronation compared with neutral running shoes. Physical fatigue was induced through an individualized submaximal running protocol on a motorized treadmill using rate of perceived exertion and heart rate monitoring. The statistical analyses indicated significant main effects of “footwear” for peak ankle inversion, peak ankle eversion, and peak hip internal rotation angles (p<0.03; d = 0.46–0.95). Pair-wise comparisons revealed a significantly greater peak ankle inversion angle (p<0.03; d = 0.95; 2.70°) and smaller peak eversion angle (p<0.03; d = 0.46; 2.53°) when running with anti-pronation shoes compared with neutral shoes. For kinetic data, significant main effects of “footwear” were found for peak ankle dorsiflexor moment, peak knee extensor moment, peak hip flexor moment, peak hip extensor moment, peak hip abductor moment, and peak hip internal rotator moment (p<0.02; d = 1.00–1.79). For peak positive hip power in sagittal and frontal planes and peak negative hip power in horizontal plane, we observed significant main effects of “footwear” (p<0.03; d = 0.92–1.06). Pairwise comparisons revealed that peak positive hip power in sagittal plane (p<0.03; d = 0.98; 2.39 w/kg), peak positive hip power in frontal plane (p = 0.014; d = 1.06; 0.54 w/kg), and peak negative hip power in horizontal plane (p<0.03; d = 0.92; 0.43 w/kg) were greater with anti-pronation shoes. Furthermore, the statistical analyses indicated significant main effects of “Fatigue” for peak ankle inversion, peak ankle eversion, and peak knee external rotation angles. Pair-wise comparisons revealed a fatigue-induced decrease in peak ankle inversion angle (p<0.01; d = 1.23; 2.69°) and a fatigue-induced increase in peak knee external rotation angle (p<0.05; d = 0.83; 5.40°). In addition, a fatigue-related increase was found for peak ankle eversion (p<0.01; d = 1.24; 2.67°). For kinetic data, we observed a significant main effect of “Fatigue” for knee flexor moment, knee internal rotator moment, and hip extensor moment (p<0.05; d = 0.83–1.01). The statistical analyses indicated significant a main effect of “Fatigue” for peak negative ankle power in sagittal plane (p<0.01; d = 1.25). Finally, we could not detect any significant footwear by fatigue interaction effects for all measures of joint kinetics and kinematics. Running in anti-pronation compared with neutral running shoes produced lower peak moments and powers in lower limb joints and better control in rear foot eversion. Physical fatigue increased peak moments and powers in lower limb joints irrespective of the type of footwear.

Real-Time Three-Dimensional Knee Moment Estimation in Knee Osteoarthritis: Toward Biodynamic Knee Osteoarthritis Evaluation and Training

We investigated differences in knee kinetic variables (external knee adduction, flexion, internal rotation moments, and impulses) between patients with knee osteoarthritis (KOA) and healthy controls during stepping on a custom elliptical trainer; and searched knee kinetic variable candidates for real-time biofeedback and for complementing diagnosis/evaluation on the elliptical trainer based on the knee kinetic variables' associations with the knee injury and osteoarthritis outcome score (KOOS). Furthermore, we explored potential gait re-training strategies on the elliptical trainer by investigating the knee kinetic variables' associations with 3-D ankle angles. The knee kinetic variables and ankle angles were determined in real-time in a patient group of 10 patients with KOA and an age-and sex-matched control group of 10 healthy subjects. The mean peak external knee adduction moment of the patient group was 47% higher than that of the control group. The KOOS-Sports and Recreational Activities and KOOS-Pain scores were found to be significantly associated with the knee kinetic variables. All the ankle angles were associated with the knee kinetic variables. The findings support the use of the knee kinetic variables on the elliptical trainer to complement KOA diagnosis quantitatively and provide potential real-time KOA gait re-training strategies/guides.

Potential contributions of skeletal muscle contractile dysfunction to altered biomechanics in obesity

Obesity alters whole body kinematics and joint kinetics during activities of daily living which are thought to contribute to increased risk of musculoskeletal injury, development of lower extremity joint osteoarthritis (OA), and physical disability. To date, it has widely been accepted that excess adipose tissue mass is the major driver of biomechanical alterations in obesity. However, it is well established that obesity is a systemic disease affecting numerous, if not all, organ systems of the body. Indeed, obesity elicits numerous adaptations within skeletal muscle, including alterations in muscle structure (ex. myofiber size, architecture, lipid accumulation, and fiber type), recruitment patterns, and contractile function (ex. force production, power production, and fatigue) which may influence kinematics and joint kinetics. This review discusses the specific adaptations of skeletal muscle to obesity, potential mechanisms underlying these adaptations, and how these adaptations may affect biomechanics.

Exercise-induced muscle fatigue in the unaffected knee joint and its influence on postural control and lower limb kinematics in stroke patients

This study aimed to investigate the effects of exercise-induced muscle fatigue in the unaffected knee joint on postural control and kinematic changes in stroke patients. Forty participants (20 stroke patients, 20 age-matched healthy participants) were recruited. To induce fatigue, maximum voluntary isometric contractions were performed in the unaffected knee joint in a Leg Extension Rehab exercise machine using the pneumatic resistance. We measured static and dynamic balance and lower-limb kinematics during gait. Changes in postural control parameters anteroposterior sway speed and total center of pressure distance differed significantly between the stroke and control groups. In addition, changes in gait kinematic parameters knee and ankle angles of initial contact differed significantly between stroke (paretic and non-paretic) and control groups. Muscle fatigue in the unaffected knee and ankle impaired postural control and debilitates kinematic movement of ipsilateral and contralateral lower limbs, and may place the fatigued stroke patients at greater risk for falls.

Do fitness and fatigue affect gait biomechanics in overweight and obese children?

The purpose of this study was to determine how an overweight or obese child's cardiorespiratory fitness level and a state of fatigue affect gait biomechanics.

METHODS

Using a three-dimensional motion analysis system, twenty-nine (female and male) overweight and obese children aged 8-11 years walked on force plates before and after being fatigued from the Progressive Aerobic Cardiovascular Endurance Run (PACER) protocol. Joint moments were calculated for the knee and hip in the frontal and sagittal planes.

RESULTS

In a non-fatigued state, peak hip and knee adductor moments showed a negative relationship with cardiorespiratory fitness level (R²=0.26, 0.26). After the subjects were fatigued, peak hip extensor (p=0.02), peak knee extensor moments (p=0.02) and peak knee adductor moments (p=0.01) showed a significant increase.

CONCLUSION

This trend illustrates that as an overweight or obese individual's fitness improves, the lower limb joint moments in the frontal plane decrease when walking. However, with the introduction of cardiorespiratory fatigue, lower limb joint moments tend to increase in the frontal and sagittal planes. Increased joint stress may have potential implications for obese children performing physical activity, as well as for clinicians who are attempting to intervene in the cycle of obesity.

Different Effect of Local and General Fatigue on Knee Joint Stiffness

PURPOSE

This study aimed to investigate the influence of locally and generally induced fatigue on the stiffness properties of the knee joint.

METHODS

Twenty-two male (24.9 ± 4.5 yr, 1.78 ± 0.06 m, 75.4 ± 6.4 kg, 23.9 ± 1.8 kg·m) and 18 female (21.1 ± 1.5 yr, 1.66 ± 0.05 m, 63.4 ± 6.5 kg, 22.9 ± 2.5 kg·m) amateur athletes participated. Peak torque (PT) of the knee extensor musculature, muscle stiffness (MS) of the vastus lateralis, and musculoarticular stiffness (MAS) of the knee joint were assessed pre- and postlocally and generally induced fatigue (undertaken on two separate days with a 1-wk interval).

RESULTS

Males were characterized by higher values of MAS, relaxed and contracted MS, normalized PT (PT/body mass), and normalized MAS (MAS/external load) irrespective of time point (P < 0.05).

LOCALLY INDUCED FATIGUE

Contracted MS increased more (P < 0.01) and normalized PT decreased more (P = 0.03) in males than in females postfatigue. Significant increases occurred in MAS in females (P = 0.01); relaxed MS (males, P < 0.001; females, P < 0.001), contracted MS (males, P < 0.001; females, P = 0.04), and normalized MAS (males, P = 0.001; females, P = 0.01) in both sexes; and normalized contracted MS (contracted MS/external load) in males (P < 0.001). Normalized PT decreased significantly in males (P < 0.01) postfatigue.

GENERALLY INDUCED FATIGUE

Contracted MS (P = 0.01) and MAS (P = 0.05) decreased significantly in males post-fatigue.

CONCLUSION

The stiffness properties of the knee joint are influenced by locally and generally induced fatigue, with different responses being observed in males and females.

Intra-individual gait pattern variability in specific situations: Implications for forensic gait analysis

In this study, inter- and intra-individual gait pattern differences are examined in various gait situations by means of phase diagrams of the extremity angles (cyclograms). 8 test subjects walked along a walking distance of 6m under different conditions three times each: barefoot, wearing sneakers, wearing combat boots, after muscular fatigue, and wearing a full-face motorcycle helmet restricting vision. The joint angles of foot, knee, and hip were recorded in the sagittal plane. The coupling of movements was represented by time-adjusted cyclograms, and the inter- and intra-individual differences were captured by calculating the similarity between different gait patterns. Gait pattern variability was often greater between the defined test situations than between the individual test subjects. The results have been interpreted considering neurophysiological regulation mechanisms. Footwear, masking, and fatigue were interpreted as disturbance parameters, each being a cause for gait pattern variability and complicating the inference of identity of persons in video recordings.

Recovery of gait after quadriceps muscle fatigue

The aim of this study was to investigate the effect of recovery time after quadriceps muscle fatigue on gait in young adults. Forty young adults (20-40 years old) performed three 8-m gait trials at preferred velocity before and after muscle fatigue, and after 5, 10 and 20min of passive rest. In addition, at each time point, two maximal isometric voluntary contractions were preformed. Muscle fatigue was induced by repeated sit-to-stand transfers until task failure. Spatio-temporal, kinetic and muscle activity parameters, measured in the central stride of each trial, were analyzed. Data were compared between before and after the muscle fatigue protocol and after the recovery periods by one-way repeated measures ANOVA. The voluntary force was decreased after the fatigue protocol (p<0.001) and after 5, 10 and 20min of recovery compared to before the fatigue protocol. Step width (p<0.001) and RMS of biceps femoris (p<0.05) were increased immediately after the fatigue protocol and remained increased after the recovery periods. In addition, stride duration was decreased immediately after the fatigue protocol compared to before and to after 10 and 20min of rest (p<0.001). The anterior-posterior propulsive impulse was also decreased after the fatigue protocol (p<0.001) and remained low after 5, 10 and 20min of rest. We conclude that 20min is not enough to see full recovery of gait after exhaustive quadriceps muscle fatigue.

Immediate Effects of Kinesiology Taping of Quadriceps on Motor Performance after Muscle Fatigued Induction

Objectives. The purpose of this cross-sectional single-blind study was to investigate the immediate effects of Kinesiology taping of quadriceps on motor performance after muscle fatigued induction. Design. Randomized controlled cross-sectional design. Subjects. Forty-five subjects participated in this study. Participants were divided into three groups: Kinesiology taping group, placebo taping group, and nontaping group. Methods. Subjects performed short-term exercise for muscle fatigued induction, followed by the application of each intervention. Peak torque test, one-leg single hop test, active joint position sense test, and one-leg static balance test were carried out before and after the intervention. Results. Peak torque and single-leg hopping distance were significantly increased when Kinesiology taping was applied (p < 0.05). But there were no significant effects on active joint position sense and single-leg static balance. Conclusions. We proved that Kinesiology taping is effective in restoring muscle power reduced after muscle fatigued induction. Therefore, we suggest that Kinesiology taping is beneficial for fatigued muscles.

Spine buddy® supportive pad impact on single-leg static balance and a jogging gait of individuals wearing a military backpack

The Spine Buddy® supportive pad was developed to be inserted underneath military backpacks to help disperse the heavy load of the backpack. The purpose of this study was to determine the impact the additional supportive pad had on static balance and a running gait while wearing a military backpack. Forty healthy subjects (age= 27.5 + 5.6 yrs, body height= 1.78 + 0.06 m, body mass= 86.5 + 14.0 kg: mean + SD) participated in a static single-leg balance test on a force plate with each lower limb while wearing a 15.9 kg military backpack for 30 s. Following this, participants were randomized to one of two interventions: 1) Intervention, which wore the Spine Buddy® supportive pad underneath their backpack or 2) Control, with no additional supportive pad. Post-intervention measurements of static single-leg balance were then recorded. Afterwards, a similar pre vs post testing schedule and randomization scheme was used to test the impact of the supportive pad on a 5 mph jogging gait using Vicon® cameras. Within-group data were analyzed with a 2-way repeated measures ANOVA. Statistically significant differences were not seen between the control and experimental group for balance and gait variables. Preliminarily, this suggests that the Spine Buddy® supportive pad causes no deleterious effect on static balance and a jogging gait in 18-45 year-old asymptomatic individuals.

Muscle activation and knee biomechanics during squatting and lunging after lower extremity fatigue in healthy young women

Muscle activations and knee joint loads were compared during squatting and lunging before and after lower extremity neuromuscular fatigue. Electromyographic activations of the rectus femoris, vastus lateralis and biceps femoris, and the external knee adduction and flexion moments were collected on 25 healthy women (mean age 23.5 years, BMI of 23.7 kg/m(2)) during squatting and lunging. Participants were fatigued through sets of 50 isotonic knee extensions and flexions, with resistance set at 50% of the peak torque achieved during a maximum voluntary isometric contraction. Fatigue was defined as a decrease in peak isometric knee extension or flexion torque ≥25% from baseline. Co-activation indices were calculated between rectus femoris and biceps femoris; and between vastus lateralis and biceps femoris. Fatigue decreased peak isometric extension and flexion torques (p<0.05), mean vastus lateralis activation during squatting and lunging (p<0.05), and knee adduction and flexion moments during lunging (p<0.05). Quadriceps activations were greater during lunging than squatting (p<0.05). Thus, fatigue altered the recruitment strategy of the quadriceps during squatting and lunging. Lunging challenges quadriceps activation more than squatting in healthy, young women.

Real-time tracking of knee adduction moment in patients with knee osteoarthritis

BACKGROUND

The external knee adduction moment (EKAM) is closely associated with the presence, progression, and severity of knee osteoarthritis (OA). However, there is a lack of convenient and practical method to estimate and track in real-time the EKAM of patients with knee OA for clinical evaluation and gait training, especially outside of gait laboratories.

NEW METHOD

A real-time EKAM estimation method was developed and applied to track and investigate the EKAM and other knee moments during stepping on an elliptical trainer in both healthy subjects and a patient with knee OA.

RESULTS

Substantial changes were observed in the EKAM and other knee moments during stepping in the patient with knee OA.

COMPARISON WITH EXISTING METHOD(S)

This is the first study to develop and test feasibility of real-time tracking method of the EKAM on patients with knee OA using 3-D inverse dynamics.

CONCLUSIONS

The study provides us an accurate and practical method to evaluate in real-time the critical EKAM associated with knee OA, which is expected to help us to diagnose and evaluate patients with knee OA and provide the patients with real-time EKAM feedback rehabilitation training.

Effects of quadriceps muscle fatigue on stiff-knee gait in patients with hemiparesis

The relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients.

Effect of triceps surae and quadriceps muscle fatigue on the mechanics of landing in stepping down in ongoing gait

The aim of this study was to evaluate the effects of muscle fatigue of triceps surae and quadriceps muscles in stepping down in ongoing gait. We expected that the subjects would compensate for muscle fatigue to prevent potential loss of balance in stepping down. A total of 10 young participants walked over a walkway at a self-selected velocity to step down a height difference of 10-cm halfway. Five trials were performed before and after a muscle fatigue protocol. Participants performed two fatigue protocols: one for ankle muscle fatigue and another for knee muscle fatigue. Kinematics of and ground reaction forces on the leading leg were recorded. Fatigue did not cause a change in the frequency of heel or toe landing. Our results indicate that in stepping down fatigue effects are compensated by redistributing work to unfatigued muscle groups and by gait changes aimed at enhancing balance control, which was however only partially successful.

Hybrid FES-robot cooperative control of ambulatory gait rehabilitation exoskeleton

Robotic and functional electrical stimulation (FES) approaches are used for rehabilitation of walking impairment of spinal cord injured individuals. Although devices are commercially available, there are still issues that remain to be solved. Control of hybrid exoskeletons aims at blending robotic exoskeletons and electrical stimulation to overcome the drawbacks of each approach while preserving their advantages. Hybrid actuation and control have a considerable potential for walking rehabilitation but there is a need of novel control strategies of hybrid systems that adequately manage the balance between FES and robotic controllers. Combination of FES and robotic control is a challenging issue, due to the non-linear behavior of muscle under stimulation and the lack of developments in the field of hybrid control. In this article, a cooperative control strategy of a hybrid exoskeleton is presented. This strategy is designed to overcome the main disadvantages of muscular stimulation: electromechanical delay and change in muscle performance over time, and to balance muscular and robotic actuation during walking.

Experimental results in healthy subjects show the ability of the hybrid FES-robot cooperative control to balance power contribution between exoskeleton and muscle stimulation. The robotic exoskeleton decreases assistance while adequate knee kinematics are guaranteed. A new technique to monitor muscle performance is employed, which allows to estimate muscle fatigue and implement muscle fatigue management strategies. Kinesis is therefore the first ambulatory hybrid exoskeleton that can effectively balance robotic and FES actuation during walking. This represents a new opportunity to implement new rehabilitation interventions to induce locomotor activity in patients with paraplegia.

Acronym list: 10mWT: ten meters walking test; 6MWT: six minutes walking test; FSM: finite-state machine; t-FSM: time-domain FSM; c-FSM: cycle-domain FSM; FES: functional electrical stimulation; HKAFO: hip-knee-ankle-foot orthosis; ILC: iterative error-based learning control; MFE: muscle fatigue estimator; NILC: Normalized stimulation output from ILC controller; PID: Proportional-Integral-derivative Control; PW: Stimulation pulse width; QUEST: Quebec User Evaluation of Satisfaction with assistive Technology; SCI: Spinal cord injury; TTI: torque-time integral; VAS: Visual Analog Scale.

Quadriceps and hamstrings morphology is related to walking mechanics and knee cartilage MRI relaxation times in young adults

STUDY DESIGN

Controlled laboratory study using a cross-sectional design.

OBJECTIVES

To analyze the relationship of quadriceps-hamstrings and medial-lateral quadriceps anatomical cross-sectional area (ACSA) ratios with knee loads during walking and articular and meniscal cartilage composition in young, healthy subjects.

BACKGROUND

Muscle forces affect knee loading during walking, but it is not known if muscle morphology is associated with walking mechanics and cartilage composition in young subjects.

METHODS

Forty-two knees from 27 young, healthy, active volunteers (age, 20-35 years; body mass index, <28 kg/m(2)) underwent 3-T magnetic resonance imaging (MRI) and 3-D motion capture. Standard MRI sequences were used for articular and meniscal cartilage T1rho and T2 relaxation times and for quadriceps and hamstrings muscle ACSA. Frontal plane kinetics during the stance phase of walking was calculated. Generalized estimating equation models were used to identify muscle variables that predicted MRI and gait parameters.

RESULTS

Quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were positively related to frontal plane loading (β = .21-.54, P≤.006), global articular cartilage relaxation times (β = .22-.28, P≤.041), and the medial-lateral ratio of meniscus T1rho relaxation time (β = .26-.36, P≤.049). The medial-lateral quadriceps ACSA ratio was positively related to global meniscus T1rho relaxation times (β = .30, P = .046).

CONCLUSION

Higher quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were associated with higher frontal plane loading during walking and with articular and meniscal cartilage T1rho and T2 relaxation times. These findings highlight the relationships between different knee tissues and knee mechanics in young, healthy individuals.

Barefoot running: an evaluation of current hypothesis, future research and clinical applications

Barefoot running has become a popular research topic, driven by the increasing prescription of barefoot running as a means of reducing injury risk. Proponents of barefoot running cite evolutionary theories that long-distance running ability was crucial for human survival, and proof of the benefits of natural running. Subsequently, runners have been advised to run barefoot as a treatment mode for injuries, strength and conditioning. The body of literature examining the mechanical, structural, clinical and performance implications of barefoot running is still in its infancy. Recent research has found significant differences associated with barefoot running relative to shod running, and these differences have been associated with factors that are thought to contribute to injury and performance. Crucially, long-term prospective studies have yet to be conducted and the link between barefoot running and injury or performance remains tenuous and speculative. The injury prevention potential of barefoot running is further complicated by the complexity of injury aetiology, with no single factor having been identified as causative for the most common running injuries. The aim of the present review was to critically evaluate the theory and evidence for barefoot running, drawing on both collected evidence as well as literature that have been used to argue in favour of barefoot running. We describe the factors driving the prescription of barefoot running, examine which of these factors may have merit, what the collected evidence suggests about the suitability of barefoot running for its purported uses and describe the necessary future research to confirm or refute the barefoot running hypotheses.

The effect of muscle fatigue on the last stride before stepping down a curb

The stride before landing may be important during stepping down. The aim of this study was to analyze variability of the kinematics and muscle activity in the final stride before stepping down a curb, with and without ankle and knee muscle fatigue. Ten young participants walked at self-selected speed and stepped down a height difference (10-cm) in ongoing gait. Five trials were performed before and after a muscle fatigue protocol (one day: ankle muscle fatigue, another day: knee muscle fatigue). The analysis focused on the trailing leg during the last but one and the last step on the higher level. Kinematics and muscle activity were recorded. Fatigue increased variability of foot-step horizontal distance in the last step on the higher level of the trailing limb, as well as in the first steps on the lower level for both limbs. This appeared due to an increase in the range of motion of the knee joint after both fatigue protocols. Participants additionally showed an increased ankle and hip ROM and decreased knee ROM. Our results suggest a loss of control under fatigue reflected in a higher variability of trailing and leading limb-step horizontal distances, with compensatory changes to limit fatigue effects, such as a redistribution of movement over joints.

Biomechanical changes at the knee after lower limb fatigue in healthy young women

BACKGROUND

The purpose of this study was to identify changes in knee kinematics, kinetics and stiffness that occur during gait due to lower limb neuromuscular fatigue.

METHODS

Kinematic, kinetic and electromyographic measures of gait were collected on healthy, young women (n=20) before and after two bouts of fatigue. After baseline gait analysis, two bouts of fatiguing contractions were completed. Fatigue was induced using sets of 50 isotonic knee extensions and flexions at 50% of the peak torque during a maximum voluntary isometric contraction. Fatigue was defined as a drop in knee extension or flexion maximum voluntary isometric torques of at least 25% from baseline. Gait analyses were completed after each bout of fatigue. Dynamic knee stiffness was calculated as the change in knee flexion moment divided by the change in knee flexion angle from 3 to 15% of the gait cycle. Co-activations of the biceps femoris and rectus femoris muscles were calculated from 3 to 15% and 40 to 52% of gait. Repeated measures analyses of variance assessed differences in discrete gait measures, knee torques, and electromyography amplitudes between baseline and after each bout of fatigue.

FINDINGS

Fatigue decreased peak isometric torque. Fatigue did not alter knee adduction moments, knee flexion angles, dynamic knee stiffness, or muscle co-activation. Fatigue reduced the peak knee extension moment.

INTERPRETATION

While neuromuscular fatigue of the knee musculature alters the sagittal plane knee moment in healthy, young women during walking, high intensity fatigue is not consistent with known mechanical environments implicated in knee pathologies or injuries.

Age-related changes in neuromuscular function of the quadriceps muscle in physically active adults

Substantial evidence exists for the age-related decline in maximal strength and strength development. Despite the importance of knee extensor strength for physical function and mobility in the elderly, studies focusing on the underlying neuromuscular mechanisms of the quadriceps muscle weakness are limited. The aim of this study was to investigate the contributions of age-related neural and muscular changes in the quadriceps muscle to decreases in isometric maximal voluntary torque (iMVT) and explosive voluntary strength. The interpolated twitch technique and normalized surface electromyography (EMG) signal during iMVT were analyzed to assess changes in neural drive to the muscles of 15 young and 15 elderly volunteers. The maximal rate of torque development as well as rate of torque development, impulse and neuromuscular activation in the early phase of contraction were determined. Spinal excitability was estimated using the H reflex technique. Changes at the muscle level were evaluated by analyzing the contractile properties and lean mass. The age-related decrease in iMVT was accompanied by a decline in voluntary activation and normalized surface EMG amplitude. Mechanical parameters of explosive voluntary strength were reduced while the corresponding muscle activation remained primarily unchanged. The spinal excitability of the vastus medialis was not different while M wave latency was longer. Contractile properties and lean mass were reduced. In conclusion, the age-related decline in iMVT of the quadriceps muscle might be due to a reduced neural drive and changes in skeletal muscle properties. The decrease in explosive voluntary strength seemed to be more affected by muscular than by neural changes.

Effects of extreme-duration heavy load carriage on neuromuscular function and locomotion: a military-based study

Trekking and military missions generally consist of carrying heavy loads for extreme durations. These factors have been separately shown to be sources of neuromuscular (NM) fatigue and locomotor alterations. However, the question of their combined effects remains unresolved, and addressing this issue required a representative context.