Treadmill Speed Research Articles

Self-selected speed provides more accurate human gait kinematics and spatiotemporal parameters than overground simulated speed on a treadmill: a cross-sectional study

BackgroundWalking speed, a key element of gait analysis, is essential for evaluating the biomechanics of the musculoskeletal system and is typically assessed on flat surfaces, such as walkways or treadmills. While many authors have compared the differences and similarities between treadmill and overground walking, no studies have yet investigated the differences between treadmill gait analysis at self-selected speed (SS) and overground simulated speed (OS). The hypothesis is that accurate kinematic measurements depend on selecting the correct gait speed; however, a mismatch between the perceived comfortable treadmill speed and actual overground speed may affect the accuracy of treadmill gait analyses. This study aimed to assess treadmill gait in healthy young adults by comparing the SS with the OS. The objectives were to determine whether participants could match SS with OS on a treadmill, examine sex differences in gait kinematics and spatiotemporal parameters (KSP) at different speeds, and identify which speed better reflects natural gait kinematics.MethodsA total of 60 healthy men and 70 healthy women, aged 22–35 years, participated in this cross-sectional study to investigate the gait kinematics and spatiotemporal differences between the SS and OS. Student’s t-test, Bonferroni adjustment, Cohen’s effect size, and quadratic regression were employed to analyse differences across walking speeds and groups.ResultsA discrepancy between OS and SS was observed in 66.4% of the participants. Our findings revealed that the adjusted R² values for KSP at SS were consistently greater than those at OS, suggesting that SS offers a more robust and accurate representation of gait kinematics, whereas OS is less reliable.ConclusionsThese findings underscore the importance of individualized speed selection in gait analysis, as it significantly impacts the accuracy of kinematic and spatiotemporal measurements. This insight is pivotal for clinicians and researchers to develop more effective rehabilitation strategies and comprehensively understand gait dynamics.

Ventilatory And Pulmonary Responses At Various Treadmill Speed With Different Breathing Methods

Ventilatory And Pulmonary Responses At Various Treadmill Speed With Different Breathing Methods

Evaluation of a finite state machine algorithm to measure stepping with ankle accelerometry: performance across a range of gait speeds, tasks, and individual walking ability.

Wearable sensors, including accelerometers, are a widely accepted tool to assess gait in clinical and free-living environments. Methods to identify phases and subphases of the gait cycle are necessary for comprehensive assessment of pathological gait. The current study evaluated the accuracy of a finite state machine (FSM) algorithm to detect strides by identifying gait cycle subphases from ankle-worn accelerometry. Algorithm performance was challenged across a range of speeds (0.4-2.6 m/s), task conditions (e.g., single- and dual-task walking), and individual characteristics. Specifically, the study included a range of treadmill speeds in young adults and overground walking conditions in older adults with neurological disease. Manually counted and algorithm-derived stride detection from acceleration data were evaluated using error analysis and Bland-Altman plots for visualization. Overall, the algorithm successfully detected strides (>96% accuracy) across gait speed ranges and tasks, for young and older adults. The accuracy of an FSM algorithm combined with ankle-worn accelerometers, provides an analytical approach with affordable and portable tools that permits comprehensive assessment of gait unbounded by setting and proves to perform well in in walking tasks characterized by variable walking. These algorithm capabilities and advancements are critical for identifying phase dependent gait impairments in clinical and free-living assessment.

Differences in acute responses and chronic adaptations according to the exercise intensity reference method in previously inactive individuals

During prolonged continuous exercise, the relationship between external load (e.g., running speed) and internal load [e.g., heart rate (HR)] shifts. This means, for example, that at a given running speed, the HR will continuously increase, whereas if the goal of the exercise is to maintain a constant HR, the running speed will decrease over time. The time dependence of the internal/external load relationship could lead to different acute responses and chronic adaptations depending on the exercise intensity reference method. This hypothesis was tested in the present study. Forty-three previously inactive individuals were randomized into two groups: one group (SPEED-C) trained at a speed midway between the first and second lactate threshold (v ∆ 50LT), whereas the other group (HR-C) trained at a HR midway between the thresholds (HR ∆ 50LT). Both groups performed 30 min of continuous endurance exercise 3 times per week for 8 weeks. Maximal oxygen consumption (V̇O2max) and peak treadmill speed (Vpeak) were determined by an incremental treadmill test followed by a verification test before (PRE) and after (POST) the 8 weeks of training. V̇O2, HR, speed, and rate of perceived exertion (RPE; measured with the Borg CR10) were recorded during the first and last treadmill training sessions performed in the lab. After POST, an additional simulated session was performed with the intensity adjusted to the new training level. Thirty-four participants (9 women and 7 men in SPEED-C; 11 women and 7 men in HR-C) completed the study and were included in the analysis. v ∆ 50LT/HR ∆ 50LT occurred at 74 ± 5% of HRmax, 63 ± 4% of V̇O2max, and 60 ± 4% of V̇peak in SPEED-C and at 74 ± 5 % of HRmax, 63 ± 5% of V̇O2max, and 60 ± 6 % of V̇peak in HR-C. SPEED-C showed higher speed (+1.5 km/h, p < 0.001), V̇O2 (+6.3 mL/kg/min, p < 0.001), HR (+23 bpm, p < 0.001) and RPE (+1.9 points, p = 0.002) than HR-C during the first training session. These initial differences between groups were reduced after 8 weeks of training (speed: by -0.5 km/h, p = 0.006; V̇O2: by -2.6 mL/kg/min, p < 0.001; HR: by -14 bpm, p < 0.001; RPE: (-1.7 points, p = 0.002). However, statistically significant reductions were no longer observed when the intensity was adjusted to the new training level. V̇O2max (+1.0 mL/kg/min, p = 0.021) and Vpeak (+0.8 km/h, p < 0.001) improved more in SPEED-C than in HR-C. Among the secondary physiological characteristics investigated in this study, speed at the second lactate threshold (+1.1 km/h, p < 0.001) and v ∆ 50LT (+0.5 km/h, p = 0.008) improved more in SPEED-C than in HR-C, whereas HR at the second lactate threshold improved more in HR-C than in SPEED-C (-7 bpm, p = 0.008). The exercise intensity reference method (speed vs. HR) affects acute responses and chronic adaptations in previously inactive individuals. However, training conditioning may mitigate these differences if the intensity is not constantly adjusted to the new training level.

Pushing the limit to reach meaningful change: the impact of intensity-driven exercise on clinical outcomes for individuals with Parkinson’s disease. A single-subject design

Purpose Parkinson’s disease creates an inability to perform previous learned autonomic tasks, such as walking, which worsens with disease progression. Recommendations to incorporate exercise at moderate to high intensities for this population has been established but there is limited knowledge about its impact on clinical based outcomes. The purpose of this research is to investigate the effectiveness of a 6-week intensity-driven walking program on clinical-based outcomes in individuals with PD. Materials/Methods Five individuals with PD were recruited for this single-subject withdrawal design (A-B-A-B) study. 6-minute walk performance and other core neurological measures of gait were collected. Intervention phases incorporated a 30-minute individualized intensity-driven treadmill walking program practiced at 65% or more of ones maximum heart rate. Increased treadmill speed, incline, and resistance were manipulated to reach the target heart rate zone. Results 6-minute walk test within condition visual analysis demonstrated a therapeutic change during intervention phases and a countertherapeutic change during withdraw periods for all 5 individuals. An abrupt therapeutic effect was demonstrated for all individuals between conditions with the percent of nonoverlapping data ranging from 70-90%. Band method analysis revealed a range of 9-19 sessions two standard deviations above baseline mean performances for all individuals. Conclusion To achieve sufficient walking performance, gait practiced at higher intensity levels may provide the optimal solution as an adjunct to standard care for individuals with PD who want to improve their walking.

Design and development of a feedback system for automatic treadmill speed adaptation

Treadmills with automatic speed adjustment offer a unique advantage: they can mimic outdoor conditions for specific training or testing protocols. This versatility makes them highly applicable in both sports and rehabilitation settings. This study presents a novel framework based on a feedback control loop system, conceived to control a treadmill belt speed using a non-invasive and low-cost sensor (Microsoft Kinect) to detect the users’ position and avoid object obstruction issues. The speed of the treadmill belt is regulated according to the user’s speed, by means of a proportional-integrative-derivative (PID) controller and a parabolic gain function. By tuning the gain function parameters, the user can customize the response of the treadmill. Position data collected during exercise using the Microsoft Kinect sensor was compared with that collected with a stereophotogrammetric motion capture system, showing promising results in terms of accuracy in position assessment. The comparison highlighted a 0.9 degree of correlation between the two systems during the running and cross-country indoor skiing tests performed. In addition, upon considering the relationship between the differences and averages of the two measures, no systematic bias was identified. The system proved to be functional for running and cross-country skiing, and it can therefore re-create similar typical characteristics of outdoor environments (e.g., speed and slope) thanks to the non-invasive user’s position detection and the customizable gain function.

Energy management in gyms microgrid: Nonlinear control of stationary bikes and treadmills with parallel rectifiers and AC/DC conversion

This article presents the complete design of a nonlinear control system for multiple stationary bikes connected to a mechanical energy conversion system equipped with squirrel cage induction generators (SIGs) linked to AC/DC converters. The primary objective of this study is to investigate the feasibility of powering multiple treadmills using the DC bus via DC/AC converters. The novelty of our approach lies in the integration of a new strategy of control system to achieve multiple control objectives within a gym microgrid environment, and an energy management algorithm to ensure the energy flow between intermittent generation and the considered, somewhat random, demand. The system is composed of several subsystems: i) stationary bikes connected to the DC bus via inverters acting as intermittent power sources; ii) a Li-ion battery-based energy storage system interfaced through a Buck-Boost converter; iii) electromechanical loads, including treadmills, powered by DC/AC converters, in addition to other DC loads. The main control objectives are as follows: a) each stationary bike extracts energy from the DC network by regulating the torque applied by the athlete, ensuring that the torque follows the reference torque; b) the treadmill’s speed must follow the reference generated based on the athlete’s condition; c) ensuring the protection of the energy storage system by monitoring its current and voltage; d) all mentioned objectives are achieved while maintaining the DC bus voltage at a reference value. To achieve these objectives, a nonlinear control approach based on Lyapunov theory is used to design the controllers. A formal analysis is conducted to assess the performance of the studied system. The system’s performance is demonstrated using the MATLAB/Simulink environment. Numerous simulations demonstrate that every control objective is achieved. Specifically, the system maintained the DC bus voltage at 500 V with a maximum deviation of 1 V, and the treadmill speed followed the reference within a margin of 0.1 m/s.

Differential expression of genes in the RhoA/ROCK pathway in the hippocampus and cortex following intermittent hypoxia and high-intensity interval training.

Structural neuroplasticity such as neurite extension and dendritic spine dynamics is enhanced by brain-derived neurotrophic factor (BDNF) and impaired by types of inhibitory molecules that induce growth cone collapse and actin depolymerization, for example, myelin-associated inhibitors, chondroitin sulfate proteoglycans, and negative guidance molecules. These inhibitory molecules can activate RhoA/rho-associated coiled-coil containing protein kinase (ROCK) signaling (known to restrict structural plasticity). Intermittent hypoxia (IH) and high-intensity interval training (HIIT) are known to upregulate BDNF that is associated with improvements in learning and memory and greater functional recovery following neural insults. We investigated whether the RhoA/ROCK signaling pathway is also modulated by IH and HIIT in the hippocampus, cortex, and lumbar spinal cord of male Wistar rats. The gene expression of 25 RhoA/ROCK signaling pathway components was determined following IH, HIIT, or IH combined with HIIT (30 min/day, 5 days/wk, 6 wk). IH included 10 3-min bouts that alternated between hypoxia (15% O2) and normoxia. HIIT included 10 3-min bouts alternating between treadmill speeds of 50 cm·s-1 and 15 cm·s-1. In the hippocampus, IH and HIIT significantly downregulated Acan and NgR2 mRNA that are involved in the inhibition of neuroplasticity. However, IH and IH + HIIT significantly upregulated Lingo-1 and NgR3 in the cortex. This is the first time IH and HIIT have been linked to the modulation of plasticity-inhibiting pathways. These results provide a fundamental step toward elucidating the interplay between the neurotrophic and inhibitory mechanisms involved in experience-driven neural plasticity that will aid in optimizing physiological interventions for the treatment of cognitive decline or neurorehabilitation.NEW & NOTEWORTHY Intermittent hypoxia (IH) and high-intensity interval training (HIIT) enhance neuroplasticity and upregulate neurotrophic factors in the central nervous system (CNS). We provide evidence that IH and IH + HIIT also have the capacity to regulate genes involved in the RhoA/ROCK signaling pathway that is known to restrict structural plasticity in the CNS. This provides a new mechanistic insight into how these interventions may enhance hippocampal-related plasticity and facilitate learning, memory, and neuroregeneration.

Exploring the impact of hyperlipidemia on cardio-motor function and exercise adaptability in Hispanic-Latinos living with HIV

HIV may precipitate a myriad of health-related complications, potentially culminating in disabilities that detrimentally affect the quality of life. Certain conditions, such as hyperlipidemia (LP), which are exacerbated by HIV, can pose additional difficulties for this particular demographic. The aim of this study is to investigate the influence of LP on the cardio-motor profile of Hispanic Latinos living with HIV. The methodology of this study consisted of a submaximal cardiovascular assessment (Ross Test) to collect relevant cardio-motor data for this research. These data were sourced from the records of individuals registered at La Perla de Gran Precio Community Centre for HIV in San Juan, Puerto Rico. The motor profile captured included treadmill speed and incline. Cardiovascular parameters recorded were blood pressure and heart rate at the cessation of the Ross Test. A total of 291 participants were classified into 229 in the non-LP group and 62 in the LP group. The findings of this study showed similar average CD4 counts. An ANOVA analysis revealed significant differences (P < 0.05) in the LP group, including decreased cardio time and treadmill incline compared to their counterparts. Hispanic Latinos living with HIV and LP exhibit notable deficits in motor gait. Gait parameters are particularly compromised in individuals affected by both conditions. The practical implication is to alert healthcare providers to integrate the specific cardio-motor assessments discussed in this study to address the factors influencing gait, which in turn may impact the quality of life of those with HIV.

A modified step-ramp-step protocol to prescribe constant-speed exercise in treadmill running.

This study investigated whether a running-adapted version of the cycling-based "step-ramp-step" (SRS) protocol would improve prediction of O2 in treadmill exercise compared to the traditional prescriptive approach. Fourteen healthy individuals (6 females; 25 ± 6years; 66.1 ± 12.7kg) performed a treadmill-based SRS protocol including a ramp-incremental test to task failure followed by two constant-speed bouts within the moderate-(MODstep-below estimated lactate threshold; θLT), and heavy-intensity domains (HVYstep-between θLT and respiratory compensation point; RCP). Using the uncorrected O2-to-speed relationship from the ramp exercise, three constant-speed bouts were performed at 40-50% between: baseline and θLT (CSEMOD); θLT and RCP (CSEHVY); and RCP and peak (CSESEV). For CSEMOD, CSEHVY, and CSESEV measured end-exercise O2 was compared to predicted O2 based on the: (i) "SRS-corrected" O2-to-speed relationship (where MODstep and HVYstep were used to adjust the O2 relative to speed); and (ii) linear "uncorrected" data. Average treadmill speeds for CSEMOD and CSEHVY were 7.8 ± 0.8 and 11.0 ± 1.4km·h-1, respectively, eliciting end-exercise O2 of 1979 ± 390 and 2574 ± 540mL·min-1. End-exercise O2 values were not different compared to SRS-predicted O2 at CSEMOD (mean difference: 5 ± 166mL·min-1; p = 0.912) and CSEHVY (20 ± 128mL·min-1; p = 0.568). The linear "uncorrected" estimates were not different for CSEMOD (-91 ± 172mL·min-1; p = 0.068) but lower for CSEHVY (-195 ± 146mL·min-1; p < 0.001). For CSESEV (running speed: 13.8 ± 1.7km·h-1), the end-exercise O2 was not different from peak O2 achieved during the ramp (3027 ± 682 vs. 2979 ± 655mL·min-1; p = 0.231). In healthy individuals, the SRS protocol more accurately predicts speeds for a target O2 compared to traditional approaches.

Acute Intermittent Hypoxia With High-Intensity Gait Training in Chronic Stroke: A Phase II Randomized Crossover Trial.

Studies in individuals with chronic stroke indicate high-intensity training (HIT) focused on walking improves locomotor function, which may be due to repeated activation of locomotor circuits and serotonin-dependent modulation of motor output. Separate studies in animals and individuals with spinal cord injury suggest acute intermittent hypoxia (AIH) can augment the effects of locomotor interventions through similar serotonin-dependent mechanisms, although no studies have coupled AIH with HIT in individuals poststroke. The goal of this study was to evaluate the safety and efficacy of AIH+HIT versus HIT alone in individuals with chronic stroke. This phase II double-blind randomized, crossover trial recruited individuals between 18 and 85 years old, >6 months poststroke, and self-selected speeds <1.0 m/s. Participants received up to 15 sessions of AIH for 30 minutes using 15 cycles of hypoxia (60-90 seconds; 8%-9% O2) and normoxia (30-60 seconds; 21% O2), followed by 1 hour of HIT targeting >75% heart rate reserve. The control condition received normoxia for 30 minutes before HIT. Following the first training phase, participants performed the second phase >1 month later. The primary outcomes were self-selected speed and fastest speed, a 6-minute walk test, and peak treadmill speed. A 3-way mixed-model ANOVA assessed the effects of time, training, and order of interventions. Of 55 individuals screened, 35 were randomized to AIH+HIT or normoxia+HIT first, and 28 individuals completed both interventions, revealing greater gains in self-selected speeds (0.14 [0.08-0.18] versus 0.05 [0.01-0.10] m/s), fastest speed (0.16 [0.10-0.21] versus 0.06 [0.02-0.10] m/s), and peak treadmill speed (0.21 [0.14-0.29] versus 0.11 [0.06-0.16] m/s) following AIH+HIT versus normoxia+HIT (P<0.01) with no order effects. Greater gains in spatiotemporal symmetry were observed with AIH+HIT, with worse outcomes for those prescribed serotonin-mediated antidepressant medications. AIH+HIT resulted in greater gains in locomotor function than normoxia+HIT. Subsequent phase III trials should further evaluate the efficacy of this intervention. URL: https://clinicaltrials.gov/; Unique identifier: NCT04472442.

Development of a Stress-Free Algorithm for Control of Running Platforms Based on Neural Network Technologies

The article discusses the task of predicting human speed using neural network technologies and computer vision to minimize lags in treadmill control systems, which pose a health risk to the user. To solve this problem, a stress-free algorithm has been developed, including: predicting the position and speed of the user on the treadmill; calculating the treadmill speed based on the analysis of the user's position and movement characteristics; data collection and processing schemes for training neural network methods; and determining the necessary number of predicted frames to eliminate lags. The scientific novelty of the research lies in the development of a treadmill control algorithm that combines: computer vision technologies for recognizing the user's body model on the platform; neural networks; and machine learning methods to determine the final human speed based on combining data on the person's position in the frame and the current and predicted speed of the person. The proposed algorithm is implemented using Python libraries, and its validation was conducted during experimental studies analyzing the preceding 10 and 15 frames to predict the next 10 and 15 frames. Comparing machine learning algorithms (linear regression, decision tree, random forest, multilayer, convolutional, and recurrent neural networks) at different lengths of analyzed and predicted frames, the RandomForestRegressor algorithm showed the best accuracy in predicting position, while dense multilayer neural networks performed best in determining current speed. Experimental research has been conducted on applying the developed algorithm and models to determine human speed (achieving accuracy when forecasting in the range of 10-15 frames) as well as integrating them into treadmill control systems. Trials have shown the effectiveness of the proposed approach and the correctness of system operation under real conditions. The developed algorithm allows for not using noise-sensitive sensors that require attachment to the user's body but rather forecasting user actions through analyzing all points of the person's body to reduce lags in various human-machine systems.

Impact of Exercise Intensity on Cardiovascular Disease in a Rat Model of Hypertension: A Systematic Review and Meta-Analysis

Objective: Hypertension increases the risk of morbidity and mortality including stroke, myocardial infarction, and other serious complications. To prevent these events, regular exercise has been recommended as a nonpharmacological intervention for hypertensive patients, but the optimal exercise intensity, in response to the variation of the condition, remains a subject of investigation. Therefore, our study investigates the impact of exercise training on the disease progression in spontaneously hypertensive rats (SHR), a well-established rat model of hypertension. Specifically, we aim to perform a meta-analysis that measures the effects of low, moderate, and high-intensity exercise on at least one of the following cardiovascular variables: systolic blood pressure (SBP), mean arterial pressure (MAP), and resting heart rate (RHR). Hypothesis: We hypothesize that the meta-analysis findings will determine that treadmill training at low and moderate intensities will significantly improve SBP, MAP, and RHR in SHRs. We also anticipate that we will find that high intensity will produce less benefit due to its stress-inducing effects. Methods: We performed a meta-analysis adhering to the PRISMA guidelines. A systematic search for scientific studies was conducted in the CINAHL, EMBASE, SPORTDiscus, and SciFinder databases using the following key words: “spontaneously hypertensive rat,” and “exercise” yielded 900+ research articles. Subsequent selection of articles included studies that comprised of only treadmill running, more than 45 minutes of exercise per day during the training period, at least five days of training per week, and a duration of at least four weeks. Finally, eligible studies included at least one of the three cardiovascular parameters. Each study was categorized into low, moderate, or high intensity based on either treadmill speed or VO2 max, or both. Quantitative SBP, MAP, and RHR data were extracted from the included studies. Results: A total of 90 studies are included in this qualitative analysis, 9.6% of which include female rats. Preliminary data analysis evaluating means for each intensity determined that all levels of intensity significantly benefited the measured cardiovascular parameters. However, the degree of benefit was greater in the low and moderate intensities as compared to the high intensity. Conclusion: All levels of intensity exercise had a beneficial response to lowering cardiovascular parameters in SHR, however, low and moderate levels of intensity produced the greatest effects. The failure of high-intensity exercise to improve cardiovascular outcomes may suggest a role played by oxidative stress and merits further investigation. Further subgroup analysis based on sex, age, and duration of exercise will be conducted to determine if these confounding variables play role in modulating these benefits. This research was supported by the MJ Murdock charitable trust. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Estimating metabolic rate from ISO heart rate method and two walking equations.

Assigning a value for metabolic rate is central to heat stress assessment. ISO 8996 describes a predictive method for walking based on the American College of Sports Medicine (ACSM) method and another generalized method based on average heart rate. In addition, the US Army uses the load carriage decision aid (LCDA) predictive equation to estimate metabolic rate. The purpose of this study was to assess the accuracy/bias and precision of the ISO heart rate method and the ACSM and LCDA equations. The laboratory database included metabolic rate, heart rate, treadmill speed, and grade during a progressive heat stress protocol. Treadmill speed and grade were set to represent one of three metabolic rates. Accuracy and precision were assessed with Bland-Altman plots. All three methods had good accuracy (low bias). For precision, the ISO heart rate method had a root mean square error (RMSE) of 34 W and 11% when adjusted for repeated measures. The RMSE for two equations was 20 W and 7%. Although the heart method had less accuracy, its application is more generalizable. The heart rate method should be used below the occupational exposure limit for heat stress to avoid a bias toward higher predicted values due to heat strain.

Physiological and muscle histochemical assessment of men and women 10 km runners matched for race performance or training volume.

Women have a disadvantage for performance in long-distance running compared with men. To elaborate on inherent characteristics, 12 subelite women were matched with 12 men for training volume (M-Tm) (56.6 ± 18 vs. 55.7 ± 17 km/wk). The women were also matched to other men for a 10 km staged outdoor time trial (M-Pm) (42:36 min:s) to determine which factors could explain equal running performance. Anthropometry and treadmill tests were done. Fiber type (% Type I and Type IIA) and citrate synthase activities were analyzed in muscle biopsy samples. Consistent sex differences for both comparisons included height, weight, % body fat (P < 0.01), and hematocrit (P < 0.05). Women had lower V̇o2max and peak treadmill speed (PTS) compared with both M-Tm and M-Pm (P < 0.01). Training matched pairs had no sex difference in % PTS at race pace but compared with M-Pm women ran at a higher % PTS (P < 0.05) and %HRmax (P < 0.01) at race pace. On average, the women trained 22.9 km/wk more than M-Pm (+67.5%, P < 0.01). This training was not associated with higher V̇o2max or better running economy. Muscle morphology and oxidative capacity did not differ between groups. Percentage body fat remained significantly higher in women. In conclusion, women matched to men for training volume had slower 10 km performance (-10.5% P < 0.05). Higher training volume, more high-intensity sessions/wk, and time spent training in the 95%-100% HRmax zone may explain the higher % PTS and %HRmax at race pace in women compared with performance-matched men.NEW & NOTEWORTHY When subelite women 10 km runners were matched with male counterparts for 10 km race performance, inherent differences in % body fat, V̇o2max, Hct, and peak treadmill speed were counteracted by significantly higher training volume, more time training at higher %HRmax and consequently, higher %HRmax and %PTS at race pace. Citrate synthase activity and muscle fiber types did not differ. When women and men matched for training, 10 km performance of men was 10.5% faster.

ASSESSMENT OF A SELF-PACED PROTOCOL FOR TESTING AEROBIC CAPACITY IN SCI INDIVIDUALS

https://youtu.be/u89x4ivgoIc BACKGROUND Underwater treadmill (UT) exercise is a recent and sparsely tested modality that may be beneficial for those with incomplete spinal cord injury (iSCI). Currently, VO2max and HRmax have not been assessed during UT exercise among those with iSCI. This study's purpose was to determine if a rating of perceived exertion (RPE) based max exertion protocol used with a motorized UT can elicit criterion-based max physiological responses among those with and without iSCI. METHODS Healthy adult males with iSCI (n=4; Age=49.8 +/- 3.9 yrs) and without iSCI (n=4; Age=50.0 +/- 7.2 yrs) participated. Borg OMNI RPE scale was used by participants to estimate intensity of exercise. Each participant reported to the lab on two occasions. On visit one, they completed informed consent papers and familiarization with the RPE scale and UT exercise. On visit two, they completed a speed-based, self-regulated incremental exercise test on the UT. Prior to all testing, the UT was filled and set to 92°F. Upon arrival, HR monitor and mask for gas collection were donned. Water height was modified to the xiphoid process. The test consisted of rest, warm-up, incremental exercise, and active recovery phases. For warm-up, treadmill speed was adjusted to 0.5 mph for 3 minutes. After walking 3 minutes, speed was increased to 0.75 mph for another 3 minutes. The incremental exercise phase consisted of four stages, 3 minutes in duration, totaling 12 minutes. For each stage, participants self-selected a speed perceived to correspond to RPE levels: 3, 5, 7, and 10. Treadmill speed was hidden from participants. At each stage's start, speed was only adjusted during the first minute until reaching the proper RPE. During the final stage, treadmill speed could be changed freely until volitional exhaustion. The test ended when volitional exhaustion was reached, at which point the speed was lowered for an active recovery. An independent samples t-test was used to compare time (minutes) until volitional exhaustion. Separate independent samples t-tests were used to compare the highest achieved HR and VO2 values. RESULTS All iSCI participants achieved a VO2peak. Only 1 participant without iSCI achieved a VO2max. Mean VO2 was significantly lower, t(6)=3.81, p=.027, for those with iSCI (13.88 +/- 10.57 mL/kg/min) than those without iSCI (34.50 +/- 2.38 mL/kg/min). CONCLUSION This study shows that the UT is a safe modality for graded exercise testing for those with and without iSCI. An RPE-regulated protocol may not be effective for eliciting criterion-based maximal aerobic results with the UT, but was well tolerated by those with iSCI. Those with iSCI may have lacked lower limb strength to achieve max workloads. Being able to use the UT to test peak aerobic fitness allows clinicians to track improvements in economy following UT training. More research of this modality is encouraged with larger samples to further evaluate potential testing protocols among this population.

Performance-Determining Variables of a Simulated Sprint Cross-Country Skiing Competition.

To investigate performance-determining variables of an on-snow sprint cross-country skiing competition and the evolvement in their relationship with performance as the competition progresses from the individual time trial (TT) to the final. Sixteen national-level male junior skiers (mean [SD] age, 18.6 [0.8]y; peak oxygen uptake [VO2peak], 67.6 [5.5]mL·min-1·kg-1) performed a simulated sprint competition (1.3km) in the skating style, comprising a TT followed by 3 finals (quarterfinals, semifinals, and final) completed by all skiers. In addition, submaximal and incremental roller-ski treadmill tests, on-snow maximal speed tests, and strength/power tests were performed. VO2peak and peak treadmill speed during incremental testing and relative heart rate, rating of perceived exertion, blood lactate concentrations, and gross efficiency during submaximal testing were all significantly correlated with performance in the TT and subsequent finals (mean [range] r values: .67 [.53-.86], all P < .05). Relative VO2peak and submaximal relative heart rate and blood lactate concentration were more strongly correlated with performance in the semifinals and final compared with the TT (r values: .74 [.60-.83] vs 0.55 [.51-.60], all P < .05). Maximal speed in uphill and flat terrain was significantly correlated with performance in the TT and subsequent finals (r values: .63 [.38-.70], all P < .05), while strength/power tests did not correlate significantly with sprint performance. VO2peak and high-speed abilities were the most important determinants of sprint cross-country skiing performance, with an increased importance of VO2peak as the competition format progressed toward the final.

MAXIMAL EXERCISE CAPACITY IS INVERSELY RELATED TO INCIDENT PERIPHERAL ARTERY DISEASE

https://youtu.be/wLtxZn3XafA BACKGROUND Maximal exercise capacity (EC) is a strong, independent predictor of incident coronary and cerebrovascular disease. However, less is known about the relationship between EC and incident peripheral artery disease (PAD). Using data from the Henry Ford Exercise Testing (FIT) Project, we evaluated the relationship between EC and incident PAD. We hypothesized that EC, measured in metabolic equivalents of task (METs), is inversely related to incident PAD. METHODS We assessed 41,268 patients (age = 55±12 yrs, 49% female, and 64% white) who completed a clinically indicated exercise stress test between January 1991 and June 2009 at a Henry Ford Health facility. Patients with established PAD at the time of testing were excluded. METs were estimated from peak treadmill speed and grade and standardized to the equivalent of a 50-year-old male to account for differences in absolute risk for a given MET level by age and sex. METs were categorized as &amp;lt;6, 6-9, 10-11, and &amp;gt;12. ICD9 codes 440.XX and 443.9 were used to identify first incidence of PAD from the test date through June 2010. Multivariable Cox regression was used to relate METs to incident PAD. Patients were censored at the date of death or last clinic visit. RESULTS During a median follow-up of 7.1 years (IQR 4.2-11.1 yrs) there were 2,596 (6%) incident diagnoses of PAD. In the adjusted analysis, each 1 MET increase in maximal EC was associated with a 7% lower risk of PAD (aHR=0.93 [0.91, 0.94]). There was a graded, inverse risk of incident PAD by MET category (see Table). A significant interaction was noted for race (overall p=.04; white [HR=0.93 (0.92, 0.95)] vs black [HR=0.91 (0.88, 0.93)], p=.02; white vs other [HR=0.97 (0.87, 1.07)], p=0.47), but not for sex (p=.79). CONCLUSION In a diverse cohort that completed a clinically indicated exercise stress test, higher EC measured in METs, is independently and inversely associated with a lower risk of incident PAD.

Metabolic Costs of Walking with Weighted Vests.

The US Army Load Carriage Decision Aid (LCDA) metabolic model is used by militaries across the globe and is intended to predict physiological responses, specifically metabolic costs, in a wide range of dismounted warfighter operations. However, the LCDA has yet to be adapted for vest-borne load carriage, which is commonplace in tactical populations, and differs in energetic costs to backpacking and other forms of load carriage. The purpose of this study is to develop and validate a metabolic model term that accurately estimates the effect of weighted vest loads on standing and walking metabolic rate for military mission-planning and general applications. Twenty healthy, physically active military-age adults (4 women, 16 men; age, 26 ± 8 yr old; height, 1.74 ± 0.09 m; body mass, 81 ± 16 kg) walked for 6 to 21 min with four levels of weighted vest loading (0 to 66% body mass) at up to 11 treadmill speeds (0.45 to 1.97 m·s -1 ). Using indirect calorimetry measurements, we derived a new model term for estimating metabolic rate when carrying vest-borne loads. Model estimates were evaluated internally by k -fold cross-validation and externally against 12 reference datasets (264 total participants). We tested if the 90% confidence interval of the mean paired difference was within equivalence limits equal to 10% of the measured walking metabolic rate. Estimation accuracy, precision, and level of agreement were also evaluated by the bias, standard deviation of paired differences, and concordance correlation coefficient (CCC), respectively. Metabolic rate estimates using the new weighted vest term were statistically equivalent ( P < 0.01) to measured values in the current study (bias, -0.01 ± 0.54 W·kg -1 ; CCC, 0.973) as well as from the 12 reference datasets (bias, -0.16 ± 0.59 W·kg -1 ; CCC, 0.963). The updated LCDA metabolic model calculates accurate predictions of metabolic rate when carrying heavy backpack and vest-borne loads. Tactical populations and recreational athletes that train with weighted vests can confidently use the simplified LCDA metabolic calculator provided as Supplemental Digital Content to estimate metabolic rates for work/rest guidance, training periodization, and nutritional interventions.

Factors affecting the efficiency of walking independence in patients with subacute stroke following robot-assisted gait training with conventional rehabilitation.

Factors affecting the efficiency of walking independence in patients with subacute stroke following robot-assisted gait training (RAGT) and conventional treatment (RAGT-CT) were examined. This retrospective cohort study included 37 patients with stroke [ n = 11 ischemic; n = 26 hemorrhagic; median poststroke interval, 28 days (interquartile range, IQR, 24-42)] who underwent RAGT using Welwalk for a median of 3 weeks (IQR, 2-4) followed by conventional training (median, 129 days; IQR, 114-146). The primary outcome was the change in functional independence measure (FIM)-walk item score from before to after RAGT (FIM-walk efficiency). The secondary outcome was the FIM-walk score at discharge. The independent variables included sensorimotor function [lower extremity (LE) motor and sensory scores and trunk function from the Stroke Impairment Assessment Set (SIAS) and Berg Balance Scale (BBS)] and cognitive function (FIM-cognitive, MMSE and Cognitive-related Behavioral Assessment) before RAGT-CT and RAGT dose duration per session, total steps and average treadmill speed at week 1, and number of sessions). We first determined the bivariate associations of each independent variable with the FIM-walk efficiency at the end of the RAGT period as decided by the therapists and with the FIM-walk score at discharge. Hierarchical multiple regression revealed that only the FIM-cognitive score was a significant predictor of the FIM-walk efficiency at the end of the RAGT period ( β = 0.47; P < 0.01, adjusted R2 = 0.21) after accounting for age, days post-stroke, SIAS-total lower extremity (SIAS-LE) motor score, and number of RAGT sessions (all nonsignificant). Furthermore, only the SIAS-trunk score was a significant predictor of the FIM-walk score at discharge ( β = 0.52; P < 0.01; adjusted R2 = 0.65) after accounting for age, days post-stroke, FIM-cognitive score, SIAS-LE motor score, and average treadmill speed at week 1 (all nonsignificant). Although patients with better cognition at the start of locomotor training achieved the pragmatic targets for terminating RAGT and proceeding with conventional therapy at a faster rate, the outcome at discharge is mainly dependent on early trunk function.