Cadence matters: Influence of cadence on spinal load during running.

BACKGROUND: Running exposes the body to physiological and mechanical stresses that generate musculoskeletal injuries, such as low back pain due to large spinal loading. Increasing running cadence may reduce impact forces and spinal shrinkage. RESEARCH QUESTION: This study aimed to determine the relationship between spinal loading and running cadence. METHODS: This cross-sectional study included 15 runners from the local community (36 ± 11 years; 23 ± 2 kg.m-2, and 8 ± 9 years of running experience) who ran for 30 min (R30) and 60 min (R60) at a constant speed (10 km.h-1). The spinal loading was assessed via fine stature variation measurements before the run (baseline) at R30 and R60. Cadence was monitored via a wristwatch. The cadence ranged from 150 to 180 steps.min-1. A t-test was used to compare stature loss between R30 and R60 (relative to baseline), and a stepwise linear regression equation was used to identify the relationship between cadence and stature variation in each instant. RESULTS: There was a stature loss throughout the race (R30 = 5.27 ± 1.92 mm and R60 =7.51 ± 2.51 mm). A linear regression analysis revealed a negative relationship between stature loss and cadence, indicating that running at a faster cadence produces smaller spinal loading than running at slower cadences after R60 (R2 = 0.38; p<0.05). SIGNIFICANCE: Increasing running cadence might cause less spinal loading than running with a slower cadence, which may reduce the risk of injury and back disorders in runners.

Moving from stable standing to single-limb stance or an up-on-the-toes position: The importance of vision to dynamic balance control.

Understanding the contribution vision has to dynamic balance control may help in understanding where/why loss of balance occurs during everyday locomotion. The current study determined how body-centre-of-mass (BCoM) dynamics and postural stability when moving to and holding a single-limb-stance (SS) or an up-on-the-toes (UTT) position were affected by visual occlusion. From standing on a force platform, 18 adults (mean (SD) 26.7 (4.8) years; 1.73 (0.08) m; 84.0 (22.9) kg; 7 females) completed repeated trials (x3) with and without vision in which they moved to either a SS or an UTT position (order countered-balanced), and attempted to hold that position for 2 (SS) or 5 (UTT) seconds before returning to standing. UTT trials were also repeated at a fast speed, and SS trials were repeated using both the dominant and non-dominant limb. BCoM dynamics were assessed by analysing the displacement and peak velocity of the centre-of-pressure (CoP) when moving to and from the SS and UTT positions. Balance stability was the variability in the CoP displacement/velocity when holding these positions. Results indicate that under visual occlusion, the peak CoP velocity when moving to the SS or UTT position was reduced (ES, 0.67 and 0.68, respectively), suggesting greater caution. Both the variability in the CoP displacement/velocity when holding these positions and the peak CoP velocity when returning to flat-standing increased (SS: ES, 1.0 and 0.86, respectively; UTT: ES 1.26 and 0.66, respectively), suggesting, respectively, greater instability and poorer control. The poorer control in SS trials, occurred when returning to standing from the SS position held on the non-dominant limb, and correspondingly, the reduction in SS duration when vision was occluded was greater for the non-dominant limb trails (limb-vision interaction; p = 0.042). This suggests that movements initiated/controlled by the non-dominant limb are more reliant on visual feedback than those initiated/controlled by the dominant limb.

Carbohydrate mouth rinse failed to reduce central fatigue, lower perceived exertion, and improve performance during incremental exercise.

We examined if carbohydrate (CHO) mouth rinse may reduce central fatigue and perceived exertion, thus improving maximal incremental test (MIT) performance. Nine recreational cyclists warmed up for 6 min before rinsing a carbohydrate (CHO) or placebo (PLA) solution in their mouth for 10 s in a double-blind, counterbalanced manner. Thereafter, they performed the MIT (25 W·min-1 increases until exhaustion) while cardiopulmonary and ratings of perceived exertion (RPE) responses were obtained. Pre- to post-MIT alterations in voluntary activation (VA) and peak twitch torque (Tw) were determined. Time-to-exhaustion (p = 0.24), peak power output (PPO; p = 0.45), and V̇O2MAX (p = 0.60) were comparable between conditions. Neither treatment main effect nor time-treatment interaction effect were observed in the first and second ventilatory threshold when expressed as absolute or relative V̇O2 (p = 0.78 and p = 0.96, respectively) and power output (p = 0.28 and p = 0.45, respectively) values, although with moderate-to-large effect sizes. RPE increased similarly throughout the tests and was comparable at the ventilatory thresholds (p = 0.56). Despite the time main effect revealing an MIT-induced central and peripheral fatigue as indicated by the reduced VA and Tw, CHO mouth rinse was ineffective in attenuating both fatigues. Hence, rinsing the mouth with CHO was ineffective in reducing central fatigue, lowering RPE, and improving MIT performance expressed as PPO and time-to-exhaustion. However, moderate-to-large effect sizes in power output values at VT1 and VT2 may suggest some beneficial CHO mouth rinse effects on these MIT outcomes.

Effects of exhaustive whole-body exercise and caffeine ingestion on muscle contractile properties in healthy men.

BACKGROUND: The influence of exhaustive whole-body exercise and caffeine ingestion on electromechanical delay (EMD) has been underexplored. This study investigated the effect of exhaustive cycling exercise on EMD and other parameters of muscle contractile properties and the potential ability of caffeine to attenuate the exercise-induced impairments in EMD and muscle contractile properties. METHODS: Ten healthy men cycled until exhaustion (88±2% of V̇O2max) on two separate days after ingesting caffeine (5 mg.kg-1 of body mass) or cellulose (placebo). Parameters of muscle contractile properties of the quadriceps muscles were assessed via volitional and electrically evoked isometric contractions, performed before and 50 minutes after ingestion of the capsules, and after exercise. Muscle recruitment during volitional contractions was determined via surface electromyography. RESULTS: Exhaustive cycling exercise did not affect volitional and relaxation EMD (P>0.05) but increased evoked EMD. In addition, the exhaustive cycling exercise also increased muscle recruitment at the beginning of volitional isometric muscle contraction (P<0.05). The peak twitch force, maximal rate of twitch force development, and twitch contraction time were all compromised after exhaustive cycling exercise (P<0.05). Acute caffeine ingestion had no effect on muscle contractile properties (P>0.05), except that caffeine increased twitch contraction time at postexercise (P<0.05). CONCLUSIONS: Exercise-induced decline in peripheral components of the EMD might be compensated by an increase in the muscle recruitment. In addition, acute caffeine ingestion had minimal influence on exercise-induced changes in muscle contractile proprieties.

The role of ankle and knee muscle characteristics in spatiotemporal gait parameters at different walking speeds: A cross-sectional study.

BACKGROUND: Understanding the intricate interplay between ankle and knee muscle characteristics and their impact on gait parameters is crucial for enhancing our comprehension of human locomotion, particularly in the context of varying walking speeds among healthy young adults. RESEARCH QUESTION: The study aimed to identify the relative importance of ankle and knee flexor and extensor muscle characteristics (e.g., strength estimated by peak torque [PT] and rate of torque development [RTD]) in the spatiotemporal gait parameters and variability in self-selected (SSWS) and fast walking speeds (FWS) in healthy young adults. METHODS: One hundred and thirty-nine adults (75 men - 54% and 64 women - 46%; 29.04 ± 9.55 years) were assessed about their muscle characteristics (PT and RTD by an isokinetic dynamometer) and spatiotemporal gait parameters at different walking speeds (SSWS and FWS by an instrumented walkway). RESULTS: Data analysis indicated a weak relationship between the PT and RTD of the ankle and knee and spatiotemporal gait parameters and variability in both walking conditions (SSWS: R2 0.14-0.05; FWS: R2 0.40-0.05). The strength of the knee muscles was more relevant when walking at a self-selected speed, while the strength of the ankle muscles played a more prominent role when walking at a fast pace. SIGNIFICANCE: The findings underscore the critical role of ankle muscles (plantar and dorsiflexors) at fast walking speeds. Therefore, targeted interventions for strength and optimization of these muscles are paramount.

An Experimental Approach to Induce Trips in Lower-Limb Amputees.

Reestablishing balance after a trip is challenging for lower-limb amputees and often results in a fall. The effectiveness of reestablishing balance following a trip depends on factors such as amputation level (transtibial or transfemoral) or which limb is tripped (prosthetic or sound/lead or trailing). Understanding the recovery responses can help identify strategies to avoid a trip becoming a fall and what trip-response functionality could be designed into a prosthesis. This study presents an experimental approach for inducing unexpected trips in individuals with amputation. Tripping was manually triggered by activating an electromagnetic device to raisea polypropylene wire to obstruct (bring to a near halt) theswinging limb during its mid-swing phase. A safety harness attached to a ceiling rail ensured participants did not hit the ground if they failed to reestablish balance following the trip (i.e., it prevented a fall from occurring). One transtibial amputee completed repeated walking trials in which a trip was induced around 1 out of 15 times to avoid it being anticipated. 3D kinematics were determined via two smartphones (60Hz) using the OpenCap software, highlighting that the experimental approach induced meaningful tripping/recovery responses dependent on which limb was tripped (prosthetic or sound). The presented methodology avoids using a rigid obstacle, potentially reducing the risk of injuries, and is inexpensive and easy to set up. Importantly it permits a trip to be unexpectedly introduced during the mid-swing phase of the gait and hence provides an approach for identifying real-world trip recovery responses. When tripping the sound limb, participants could 'disentangle' from the trip-wire (post-trip) by plantarflexing the ankle, but such action was not possible when tripping the prosthetic limb.

Control of center of mass during gait of stroke patients: Statistical parametric mapping analysis.

BACKGROUND: The control of the center of mass is essential for a stable and efficient gait. Post-stroke patients present several impairments, which may compromise the control of the center of mass during gait in the sagittal and frontal planes. This study aimed to identify changes in the vertical and mediolateral behavior of the center of mass during the single stance phase of post-stroke patients using the statistical parametric mapping analysis. It also aimed to identify alterations in the center of mass trajectories regarding the motor recovery stages. METHODS: Seventeen stroke patients and 11 neurologically intact individuals were analyzed. The statistical parametric mapping approach was used to identify changes in the center of mass trajectories between stroke and healthy groups. The trajectories of the center of mass of post-stroke individuals were compared according to their motor recovery status. FINDINGS: A near-flat vertical trajectory of the center of mass was indenfitifed in the stroke group compared to their healthy counterparts, especially on the paretic side. The center of mass trajectories in both directions (vertical and mediolateral) presented substantial alteration at the end of the single stance phase in the stroke group. The trajectory of the center of mass of the stroke group was symmetrical in the mediolateral direction between the sides. The trajectories of the center of mass presented similar pattern irrespective of the motor recovery status. INTERPRETATION: The statistical parametric mapping approach showed to be suitable for determining gait changes in post-stroke individuals, irrespective of their motor recovery stage.

Time profile of kinematic synergies of stroke gait.

BACKGROUND: In stroke subjects, the motor skills differ between sides and among subjects with different levels of motor recovery, impacting inter-joint coordination. How these factors can affect the kinematic synergies over time during gait has not been investigated yet. This work aimed to determine the time profile of kinematic synergies of stroke patients throughout the single support phase of gait. METHODS: Kinematic data from 17 stroke and 11 healthy individuals was recorded using a Vicon System. The Uncontrolled Manifold approach was employed to determine the distribution of components of variability and the synergy index. To analyze the time profile of kinematic synergies, we applied the statistical parametric mapping method. Comparisons were made within the stroke group (paretic and non-paretic limbs) and between groups (stroke and healthy). The stroke group was also subdivided into subgroups with worse and better motor recovery. FINDINGS: There are significant differences in synergy index at the end of the single support phase between stroke and healthy subjects; paretic and non-paretic limbs; and paretic limb according to the motor recovery. Comparisons of mean values showed significantly larger values of synergy index for the paretic limb compared to the non-paretic and healthy. INTERPRETATION: Despite the sensory-motor deficits and the atypical kinematic behavior, stroke patients can produce joint covariations to control the center of mass trajectory in the forward progression plane, but the modulation of the synergy is impaired, reflecting altered adjustments, especially in the paretic limb of subjects with worse levels of motor recovery.

Complete recovery of quadriceps muscle peripheral fatigue after running in Olympic, but not Sprint, triathlon.

This study compared central and peripheral fatigue development between the Sprint and Olympic distance triathlon. Fifteen male triathletes performed Sprint and Olympic triathlon simulations in a randomized and counterbalanced order. Central and peripheral fatigue was evaluated from changes in voluntary activation level (VAL) and twitch responses of quadriceps muscle (Qtw,pot), respectively. Qtw,pot reduced from baseline to post-swimming similarly between triathlon simulations (Sprint,-17±11%; Olympic, -13±9%). In post-cycling, Qtw,pot further declined to a similar extent between triathlon distances (Sprint, -31±15%; Olympic, -28±11%). In post-running, Qtw,pot was fully recovered in the Olympic triathlon (-4±10%), whereas there was only a partial recovery of Qtw,pot in the Sprint triathlon (-20±11%). VAL was not reduced in post-swimming, but reduction was similar between triathlon distances in post-cycling (Sprint, -10±9%; Olympic, -8±8%) and post-running (Sprint, -15±14%; Olympic, -16±8%). In the Sprint triathlon, the swimming speed (1.07±0.13m.s-1) was above (p <.001) critical speed (1.01±0.14m.s-1), the cycling power (179.7±27.2W) was below the respiratory compensation point (216.3±27.8W, p <.001) and running speed (13.7±1.05km.h-1) similar to the respiratory compensation point (13.2±0.70km.h-1, p =.124). In the Olympic triathlon, swimming speed (1.03±0.13m.s-1) was similar to critical speed (p =.392), and cycling power (165.3±27.3W) and running speed (12.6±1.05km.h-1) were below the respiratory compensation point (p ≤.007). In conclusion, peripheral fatigue progressed until post-cycling regardless of triathlon distances. However, peripheral fatigue was fully recovered after running in Olympic but not in Sprint triathlon. The central fatigue started in post-cycling and progressed until post-running regardless of triathlon distances.HighlightsThe quadriceps muscle peripheral fatigue progresses similarly in Sprint and Olympic triathlons until post-cycling.The quadriceps muscle peripheral fatigue is completely recovered after running in the Olympic triathlon, whereas it is partially recovered in the Sprint triathlon.The central fatigue starts in post-cycling and progresses similarly until post-running in Sprint and Olympic triathlons, regardless of triathlon distances.

Are the spatiotemporal gait parameters at different walking speeds capable of predicting variations in cognitive status by the mini-mental state examination?

BACKGROUND: Several studies have reported the association between cognition and gait; however, most are limited to investigating gait in just one speed, usually the self-selected one, and commonly, only the general score of cognitive tests is used. AIMS: Investigate the relationship between the spatiotemporal gait parameters at different speeds (self-selected and fast walking speeds) and cognitive status in older adults. METHODS: Cross-sectional study. Two hundred and ninety-five older adults (70.9 ± 7.2 years; 82.3% women) were evaluated according to cognitive status (Mini-Mental State Examination, MMSE) and spatiotemporal gait parameters. RESULTS: Data analysis indicates that the spatiotemporal gait parameters (stride length, step time, and single support time) were able to predict cognitive status, assessed by the MMSE general score and its subdomain (temporal and spatial orientation) at both walking speeds. CONCLUSIONS: The spatiotemporal gait parameters were associated with cognitive status, assessed by the MMSE (general score and temporal and spatial orientation), regardless of the walking conditions. The model's variance was significant and with a large effect size. Stride length and step time were identified as the variables with the best explanatory factors. Therefore, it is concluded that greater cognitive performance is associated with longer stride lengths and faster step times.

Comparison of the Clinical-Functional Vulnerability Index and the frailty phenotype for the identification of falls in older individuals: A cross-sectional study.

BACKGROUND: Frailty increases the risk of falls, disability and death in older adults. The Cardiovascular Health Study identified a frailty phenotype (the Fried Phenotype) that was primarily based on physical domains. Instruments that incorporate additional domains (e.g., cognitive, disability or mood) may more accurately identify falls. OBJECTIVES: The study aimed i) to evaluate the association between falls and the number of phenotypes identified by the Fried Phenotype and CFVI-20 scores and ii) to compare the strength of the association between falls and each frailty instrument. METHODS: This study used the CFVI-20 and the Fried Phenotype and reported falls during the last twelve months. Logistic regression models, odds ratios (ORs), and ROC curves were used to identify associations and perform comparisons (p<0.05). The reporting of the study followed the Strobe guidelines. RESULTS: This study included 1,826 individuals (mean 70.9 (SD 7.3) years old). Prevalence of pre-frailty and low vulnerability was high (72% and 69%) and comparable between frailty instruments. The number of Fried phenotypes increased the odds of having fallen in the past 12 months (OR: 1.5 to 29.5) and the CFVI-20 scores (11% increase/unit change). The CFVI-20 identified falls more accurately than the Fried Phenotype (AUC: 0.68 vs. 0.60, p < 0.001). CONCLUSIONS: The number of phenotypes and the CFVI-20 scores were associated with falls; continuous scores identified falls more accurately than categorical classifications. The CFVI-20 was more strongly associated with falls in community-dwelling older adults than the Fried Phenotype.

Nursing Home Residence, Overweight and Cognitive Status are Related to Falls in Older Adults: A Cross-sectional Study.

BACKGROUND: Nursing home residents are likely to differ from community older adults when their gait parameters are compared, as nursing home residents present more falls. AIM: The study aim was to identify the main fall (occurrence predictors) (anthropometrics, functional and gait-related parameters) between older adults living in community and nursing homes during self-selected (SSWS) and fast walking speeds (FWS). METHODS: A hundred and sixty-five older adults were selected from the community (n = 92) and nursing home (n = 73) with and without fall history. They were assessed for fall history, functionality, cognitive status, and several gait parameters in SSWS and FWS conditions. RESULTS: Fallers differed from non-fallers in the SSWS, while such differences were not evidenced during the FWS. Cadence and stride width did not differ when living backgrounds were compared. Nursing home residents walked slower than their non-institutionalized peers, regardless of fall history or walking speed. Besides, binary logistic regression analysis showed that living in a nursing home, age, body mass index (BMI), mini-mental state examination (MMSE), and step width were related to falls in the SSWS. On the other hand, living in a nursing home, having a larger BMI and having low MMSE scores were fall predictors in the FWS. CONCLUSION: Fall occurrence can be identified by factors related to living in nursing homes, cognitive status, BMI, and gait parameters, at the SSWS. Cognitive status and BMI are related to falls in the FWS for those living in nursing homes.

Smartphones dependency risk analysis using machine-learning predictive models.

Recent technological advances have changed how people interact, run businesses, learn, and use their free time. The advantages and facilities provided by electronic devices have played a major role. On the other hand, extensive use of such technology also has adverse effects on several aspects of human life (e.g., the development of societal sedentary lifestyles and new addictions). Smartphone dependency is new addiction that primarily affects the young population. The consequences may negatively impact mental and physical health (e.g., lack of attention or local pain). Health professionals rely on self-reported subjective information to assess the dependency level, requiring specialists' opinions to diagnose such a dependency. This study proposes a data-driven prediction model for smartphone dependency based on machine learning techniques using an analytical retrospective case-control approach. Different classification methods were applied, including classical and modern machine learning models. Students from a private university in Cali-Colombia (n = 1228) were tested for (i) smartphone dependency, (ii) musculoskeletal symptoms, and (iii) the Risk Factors Questionnaire. Random forest, logistic regression, and support vector machine-based classifiers exhibited the highest prediction accuracy, 76-77%, for smartphone dependency, estimated through the stratified-k-fold cross-validation technique. Results showed that self-reported information provides insight into predicting smartphone dependency correctly. Such an approach opens doors for future research aiming to include objective measures to increase accuracy and help to reduce the negative consequences of this new addiction form.

Clinical-Functional Vulnerability, Functional Capacity, and Falls in Octogenarians with Different Physical Activity Levels-A Cross-Sectional Study.

AIM: To compare differences between frailty, functional capacity, and fall prevalence among community-dwelling oldest-old adults regarding their physical activity levels. METHODS: Two hundred and thirty-nine octogenarians (80+ years) were allocated according to their physical activity as insufficiently active (<150 min week-1; n = 98; 84.4 ± 3.7 years), active (150 to 300 min week-1, n = 81, 83.9 ± 3.1 years), and very active (>300 min week-1, n = 60; 83.8 ± 3.4 years). Frailty (CFVI-20 questionnaire), functional capacity (Five Times Sit-to-Stand Test, Timed Up and Go, Balance, and handgrip strength), fall history, and physical activity were assessed. RESULTS: The insufficiently active group was the frailest and presented the worst functional performance compared to the other groups. The fall prevalence was higher in the insufficiently active (60.9%) compared to the active (26.4%) and very active (12.7%) groups. CONCLUSIONS: The group of insufficiently active octogenarians showed the greatest frailty, worst functional capacity, and higher fall prevalence than the active and very active groups. The engagement in physical activity of at least 300 min week-1 is essential to reverse or minimize the deleterious effects of aging on frailty, functional capacity, and falls in octogenarians.

Caffeine Increases Endurance Performance via Changes in Neural and Muscular Determinants of Performance Fatigability.

PURPOSE: In the present study, we tested the hypothesis that caffeine would increase endurance performance via attenuation of neural and muscular determinants of performance fatigability during high-intensity, whole-body exercise. METHODS: Ten healthy males cycled until exhaustion (89% ± 2% of V̇O2max) after the ingestion of caffeine or placebo. During another four visits, the same exercise was performed after either caffeine or placebo ingestion but with exercise discontinued after completing either 50% or 75% of the duration of placebo trial. An additional trial with caffeine ingestion was also performed with interruption at the placebo time to exhaustion (isotime). Performance fatigability was measured via changes in maximal voluntary contraction, whereas neural and muscular determinants of performance fatigability were quantified via preexercise to postexercise decrease in quadriceps voluntary activation (VA) and potentiated twitch force, respectively. RESULTS: Compared with the placebo, caffeine increased time to exhaustion (+14.4 ± 1.6%, P = 0.017, 314.4 ± 47.9 vs 354.9 ± 40.8 s). Caffeine did not change the rate of decline in maximal voluntary contraction (P = 0.209), but caffeine reduced the twitch force decline at isotime when stimulating at single twitch (-58.6 ± 22.4 vs -45.7 ± 21.9%, P = 0.014) and paired 10 Hz electrical stimuli (-37.3 ± 13.2 vs -28.2 ± 12.9%, P = 0.025), and reduced the amplitude of electromyography signal during cycling at isotime (P = 0.034). The decline in VA throughout the trial was lower (P = 0.004) with caffeine (-0.5 ± 4.2%) than with placebo (-5.8 ± 8.5%). Caffeine also maintained peripheral oxygen saturation at higher levels (95.0 ± 1.9%) than placebo (92.0 ± 6.2%, P = 0.016). CONCLUSIONS: Caffeine ingestion improves performance during high-intensity, whole-body exercise via attenuation of exercise-induced reduction in VA and contractile function.

Association between Domains of the Clinical-Functional Vulnerability Index and Falls History in Older Adults: A Cross-Sectional Study.

Objectives: The study aimed to determine which domains, sets, and isolated or combined questions of the Clinical-Functional Vulnerability Index (CFVI-20) are associated with falls history in older adults. Methods: Instruments used were the CFVI-20 assessment and reported falls during the last year. The receiver operating characteristics (ROC) curves identified the performance of the CFVI-20 domains and questions in identifying older adults with and without falls history, while logistic regression identified relevant questions to identify fall history. Results: This study included 1725 individuals (71.9 ± 7.3 years). The area under the curve (AUC) between the CFVI-20 and fall history was 0.69. The mobility domain presented the largest AUC (0.71; p < 0.01), and most isolated domains showed low AUCs (0.51 to 0.58). Isolated questions were limited to identifying fallers. The regression analysis identified 7 questions of the CFVI-20 with falls. Conclusions: The CFVI-20 general score identified older adults with a fall history. When considered in isolation, most domains were limited to identifying falls, except for the mobility domain. Combining the CFVI-20 questions enabled identification of fallers.

Caffeine alters the breathing pattern during high-intensity whole-body exercise in healthy men.

PURPOSE: The current study investigated the effect of caffeine on the breathing pattern during a high-intensity whole-body exercise. METHODS: Using a randomized, crossover, counterbalanced, and double-blind design, twelve healthy men ingested either 5 mg.kg-1 of caffeine or cellulose (placebo) one hour before performing a high-intensity whole-body exercise (i.e., work rate corresponding to 80% of the difference between the gas exchange threshold and maximal oxygen uptake) until the limit of tolerance. Ventilatory and metabolic responses were recorded throughout the trial and at task failure. RESULTS: Caffeine ingestion increased time to task failure in relation to the placebo (368.1 ± 49.6 s vs. 328.5 ± 56.6 s, p = 0.005). Caffeine also increased tidal volume and inspiratory time throughout the exercise (p < 0.05). Compared to task failure with placebo, task failure with caffeine intake was marked by higher (p < 0.05) minute ventilation (134.8 ± 16.4 vs. 147.6 ± 18.2 L.min-1), the ventilatory equivalent of oxygen consumption (37.8 ± 4.2 vs. 41.7 ± 5.5 units), and respiratory exchange ratio (1.12 ± 0.10 vs. 1.19 ± 0.11 units). CONCLUSION: In conclusion, ingestion of caffeine alters the breathing pattern by increasing tidal volume and lengthening the inspiratory phase of the respiratory cycle. These findings suggest that caffeine affects the ventilatory system, which may account, in part, for its ergogenic effects during high-intensity whole-body exercises.

Multifactorial Assessment of Older Adults Able and Unable to Recover Balance During a Laboratory-induced Trip.

BACKGROUND: Older adults are prone to falls, and identifying fallers and non-fallers from a set of fall-related variables is essential while establishing effective preventive programs. AIMS: This study aimed to analyze if a set of parameters (i.e., strength, functional status, dynamic balance, gait, and obesity-related anthropometric measures) differ between older adults able and unable to recover from an induced trip. OBJECTIVE: To analyze predictors among older adults able and unable to identify fallers and nonfallers. METHODS: Thirty healthy old adults were tripped once during the mid-swing phase of the gait. The trip outcome was used as a criterion to assign participants to a recovery (REC; n=21; 71.2±5.7 years; 70.9±12.8 kg; 1.60±0.09 m) or a non-recovery group (NREC; n=9; 69.4±6.8 years; 85.7±11.8 kg; 1.59±0.08 m). The spatiotemporal gait parameters, functional mobility, dynamic balance, and isokinetic muscular function were measured. RESULTS: The NREC presented larger BMI (33.6±2.7 vs. 27.5±3.4 kg.m-2; p<0.05); greater time for the initiation phase on the voluntary step execution test (197.0±27.9 vs. 171.7±31.3s; p<0.05); lower plantarflexor (0.41±0.15 vs. 0.59±0.18 N.m; p<0.05), dorsiflexor (0.18±0.05 vs. 0.24±0.07 N.m; p<0.05), knee extensor (1.03±0.28 vs. 1.33±0.24 N.m; p<0.05) and knee flexor peak torques (0.50±0.15 vs. 0.64±0.13 N.m; p<0.05); and greater time up and go (8.0±0.8 vs. 7.4±0.7 s). CONCLUSION: The results showed that it is possible to identify fall risk components based on several fall-related parameters using a laboratory-induced trip as the outcome variable.

Effects of functional electro-stimulation combined with blood flow restriction in affected muscles by spinal cord injury.

Muscle atrophy is a great consequence of spinal cord injuries (SCI) due to immobility. SCI's detrimental effects on large muscle groups may lead to secondary effects such as glucose intolerance, increased risk of metabolic syndrome, and diabetes. Exercising with blood flow restriction (BFR) has been proposed as an effective method to induce hypertrophy using low training loads, with little or no muscle damage. This study investigated acute and chronic effects of low-intensity functional electrical stimulation (FES) combined with BFR on muscles affected by spinal cord injury. The acute effects of one bout of FES with (FES + BFR group) and without BFR (FES group) on muscle thickness (MT) and edema formation were compared. The chronic effects on MT and edema following 8 weeks of twice weekly training with and without BFR were also compared. The FES + BFR group showed MT and edema increases compared to the FES only group (p< 0.05). The FES + BFR showed a chronic MT increase after 4 weeks of training (p <0.05), with no further MT increases from the 4th to the 8th week (p>0.05). Following 3 weeks of detraining, MT decreased to baseline. No MT changes were observed in the FES (p>0.05). The FES + BF stimuli induced MT increases on the paralyzed skeletal muscles of SCI. The acute effects suggest that FES causes a greater metabolite accumulation and edema when combined with BFR. The early increases in MT can be attributed to edema, whereas after the 4th week, it is likely to be related to muscle hypertrophy. Register Clinical Trial Number on ReBeC: RBR-386rm8.

A cross-sectional analysis of the muscle strength, spinal shrinkage, and recovery during a working day of military police officers.

OBJECTIVE: Military personnel has a large prevalence of back pain, especially those involved in patrolling routines, as they wear heavy protective equipment. Patrolling includes long periods of sustaining the protective equipment in a sitting or in a motor vehicle (motorcycle or car). Thus, understanding spinal loading of military police officers after patrolling by car (CAR; n = 14), motorcycle (MOT; n = 14), and administrative (ADM; n = 14) routines is relevant to establish preventive strategies. METHODS: The torque of the trunk and working and anthropometric characteristics were assessed to explain spinal loading using stature variation measures. Precise stature measures were performed before and after a 6 h journey (LOSS) and 20 min after a resting posture (RECOV). The trunk extensor (PTE BM-1 ) and flexor (PTF BM-1 ) muscles' isometric peak torque were measured before the working journey. RESULTS: The LOSS was similar between CAR and MOT (4.8 and 5.8 mm, respectively) after 6 h of patrolling. The ADM presented the lowest LOSS (2.8 mm; P < .05). No changes in RECOV between groups were observed (P > .05). Vibration may explain the greater spinal loading involved in patrolling in comparison to the ADM. A GLM analysis revealed that BMI was the only explanatory factor for stature loss. No independent variables explained RECOV. The ability of the trunk muscles to produce force did not influence LOSS or RECOV. CONCLUSIONS: Military police officers involved in patrolling may require greater post-work periods and strategies designed to reduce the weight of the protective apparatus to dissipate spinal loading. The external load used in patrolling is a relevant spinal loading factor.