Step Rate Research Articles

Evidence of spontaneous cardiac-locomotor coupling during daily activities in healthy adults.

One way to improve exercise performance and protect heart health is the extended synchronization of the stepping with the diastolic phase of the cardiac cycle. Cardiac-locomotor coupling (CLC) happens when the step rate (SR) equals the heart rate (HR). The extent of CLC in daily life is unknown. This study aims to analyze spontaneous occurrences of CLC during daily activities. A retrospective analysis of daily life recordings from a wrist-worn sensor was undertaken (PMData, N = 16, 5months duration). The deviation between HR and SR was used to define CLC (deviation ≤ 1%) and weak CLC (1%< deviation ≤ 10%). The occurrence and the probability of CLC during everyday life were computed from the recordings. The CLC occurrences were stratified depending on the duration and intensity of the physical activity. Finally, a Monte Carlo simulation was run to evaluate the probability of random occurrences of CLC vs. the observed recordings. Participants couple for 5% and weakly couple for 35% of the observational period. The ratio of 1:1 between HR and SR is the dominating occurrence across the study population and this overrepresentation is significant. CLC occurs mostly for long activities. The extent of CLC for various intensities of activity is subject-dependent. The results suggest that CLC is feasible for most people. CLC occurs spontaneously during unsupervised daily activity in everyone in our cohort, which suggests a mechanistic interaction between the cardiac and the locomotor systems. This interaction should be investigated for medical rehabilitation and sports applications in the future.

Determination of moderate walking intensity using step rate and VO2 reserve in healthy men

ObjectiveThis study investigated step rates (SR) during overground walking to estimate the relative aerobic capacity that corresponds to a moderate intensity.MethodsThe present study utilized a repeated measure, within-subjects design incorporating a counterbalanced order. A total of twenty-three healthy men walked on a 119-meter oval track with artificial turf at self-selected pace (FP), 100, 120, and 140 steps/min for 6 min each while oxygen uptake (VO2), speed (in km/h), distance (in m), and steps (in steps/min) were measured.ResultsDuring FP, participants walked an average cadence of 117 ± 9.3 steps/minclose to 120 steps/min, which corresponds to 4.7 metabolic equivalents (METs). The estimated VO2 reserve was 30.5% of VO2 reserve at the FP and was close to the 120 steps/min of 33.3%. At the 100 and 140 steps/min, the VO2 reserve were 24.1% and 45.2%, respectively. The regression analysis revealed that an SR of 88.2 elicited 3METs and 17.1% of VO2reserve. Additionally, an SR of 129 elicited 5.9METs and 40% of VO2 reserve.ConclusionsThis study demonstrated that a moderate walking intensity for young, healthy men corresponded to 128.9 steps per minute. A range of 120 ~ 140 steps/min for walking could be recommended as a general guideline for moderate-intensity exercise. However, concerning providing public guidelines, caution should be taken regarding determining the moderate walking intensity due to the individual’s fitness level.

The Impact of Training Load on Running Gait Variability: A Pilot Study

Purpose: Running gait variability appears to be a new metric related to fatigue in long-distance runners. However, no study has verified the changes in gait variability over a longitudinal study involving well-experienced runners. Therefore, the aim of this study was to investigate the changes in gait variability in distance runner before and after a 9-week endurance training program. Methods: A male runner (age 23 years; body mass 58 kg; stature 1.70 m, BMI 20 kg·m−2) completed two critical speed (CS) test and six trial at different speeds (calculated by CS) with 9-week of training in-between. At the same time heart rate (HR) was continuously recorded and normalized as a percentage of the maximal heart rate (220 - age) %HRmax, serving as a proxy for metabolic expenditure. Additionally, kinematic (contact time (CT), flight time (FT), step length (SL), step rate (SR)) and kinetic measurements (leg (kvert) and vertical (kleg) stiffness), were recorded. While the running gait variability was calculated as phase coordination index (PCI). Results: CS and HR were 16.40/18.00 km·h-1 and 93.19±1.23/93.81±2.38 %HRmax in baseline and after the training, respectively. The kinematic and kinetic variables studied at different speeds (13.80-14.40-15.00-15.70-16.40-17.10 km·h-1) showed a significative training effect vs baseline conditions for CT (P= .010), FT (P= .010), SL (P= .002), SR (P= .002), kvert (P=.003), kleg (P= .0001). At the same way the metabolic demand and PCI changed significantly after the training compared to the baseline condition for average/maximum HR (P= .009 – 0.024, respectively) and PCI (P= .009). Conclusions: These results suggest that gait variability is one mechanical determinant that demonstrates the adaptation of training load when neuromuscular output related to physiological efforts is under stress conditions, such as running training. Therefore, PCI could be a useful tool for monitoring the impact of running training load on bilateral running coordination. Keywords: human locomotion; footstep pattern coordination; running performance; endurance runners.

ACUTE EFFECTS OF DYNAMIC AND PNF STRETCHING ON LEG AND VERTICAL STIFFNESS ON FEMALE GYMNASTS

The purpose of the study was to investigate the acute effect of Dynamic (DS) and PNF stretching on leg (Kleg) and vertical stiffness (Kvert) on female gymnasts. Thirty-one female athletes from various types of gymnastics (artistic, rhythmic, team gymnastics) participated in this study ([Mean ± SD] age: 22.32 ± 3.35 years, height: 164.87 ± 4.96 cm, body mass: 57.20 ± 6.54 kg) performed 30 sec running bouts at 4.44 m *s-1, under 3 different stretching protocols (PNF, DS, and no stretching [NS]). The total duration in each stretching condition was 6 minutes, and each of the 4 muscle groups was stretched for 40 seconds. Leg and vertical stiffness values were calculated using the “sine wave” method. No significant influence of stretching type on Kleg and Kvert were found after DS and PNF stretching. However, significant changes were found in Fmax, Dy, flight time (tf), step rate (SR), and step length (SL) after DS and PNF stretching protocol, indicating that DS produced greater changes compared to PNF protocol.

Physiological Capacity During Simulated Stair Climbing Evacuation at Maximum Speed Until Exhaustion

Stair-ascending at maximum ability is required during emergency evacuations to reach a safe refuge from deep underground structures. We hypothesized that an ascent can last maximum 5 min at the individual’s maximum step rate (SR), and oxygen uptake ( {dot{V}}{text{O}}_{2} ) would not reach a stable state. This study explored stair-ascending endurance and some physiological constraints of performance. Eighteen healthy volunteers with mean (standard deviation, SD) age 26.7 (4.0) years, height 172.2 (10.7) cm, weight 68.0 (11.3) kg, BSA 1.8 (0.2) m−2, {dot{V}}{text{O}}_{rm 2max} 48.5 (5.4) mL min−1 kg−1, and HRmax 192 (9) b min−1 ascended on a stair machine at a SR equivalent to their 100% {dot{V}}{text{O}}_{rm 2max} . The mean (SD) ascending duration was 3.47 (1.18) min, supporting the hypothesis. The calculated vertical height covered was 85.5 (32.1) m. The {dot{V}}{text{O}}_{rm 2highest} reached 44.8 (7.3) mL min−1 kg−1, which was 92.3 (9.7)% of {dot{V}}{text{O}}_{rm 2max} when the HRhighest peaked at 174 (11) b min−1. However, the mean ( {dot{V}}{text{O}}_{2} ) reached a relatively steady state after the sharp rise. The post-ascent blood lactate, respiratory exchange ratio, and perceived exertion values recorded were high, 14.4 (4.0) mmol l−1, 1.20 (0.09), and 18.2 (0.7), respectively, indicated that exhaustion was reached. The ascending SR rate was above the lactate threshold; therefore, the attainment of {dot{V}}{text{O}}_{rm 2} steady state was slowly reached. EMG amplitudes of four major leg muscles increased and the median frequencies of two muscles decreased significantly (p < .01) indicating local muscle fatigue (LMF). Leg LMF and hyperventilation resulted in speedy exhaustion leading to termination. These results infer that stair ascending at maximum ability (122 steps min−1) is possible to sustain 2–6 min. These overall results offer useful and vital information to consider when designing underground emergency evacuation facilities.

Physiological and Biomechanical Differences Between a Traditional Treadmill and a 360 Degree Virtual Reality Treadmill

Virtual reality opportunities are booming as technology has advanced to provide a truly immersive experience. Soon virtual reality exercise experiences may be readily available to the public; thus, the exercise equipment that companies produce need to be assessed for use and safety. PURPOSE: Fifteen college students (8 women, 8 men; 20 &#177; 1 years old) walked for 5 minutes on a traditional treadmill (TT) and a 360-degree virtual reality treadmill (VR) with no headset to determine the physiological [heart rate (HR), oxygen consumption (VO2), rate of perceived exertion (RPE), respiratory exchange ratio (RER)] and biomechanical [step rate (SR), step length (SL), knee angle (KA), tilt] differences at self-selected paces as well as to a pace of 97 steps per minute set by a metronome (TTM vs VRM). RESULTS: VO2 (TT:11.6 &#177 1.2 vs VR:16.8 &#177; 3.5 ml/kg/min, p &lt; 0.005), RER (TT:0.81 &#177; 0.5 vs VR:0.89 &#177; 0.5, p &lt; 0.005), HR (TT:91.3 &#177; 16.3 vs VR:113.1 &#177; 22.3 bpm, p &lt; 0.005) and RPE (TT:2.1 &#177; 0.8 vs VR:4.7 &#177; 1.5, p &lt; 0.005) were all significantly lower while walking on a traditional treadmill (TT) compared with a VR360 treadmill (VR) at a self-selected pace. This same pattern was observed when asked to walk at a specific cadence (97 steps/min) except RER was not different between the traditional treadmill and the VR360 treadmill (TTM: 0.89 &#177; 0.05 vs VRM: 0.94 &#177; 0.06, p=0.146). SR was significantly higher on the traditional treadmill (TT:107.1 &#177; 6.0 vs VR:76.9 &#177; 14.8 steps/min, p &lt; 0.005), as well as SL (TT:0.42 &#177; 0.07 vs VR:0.22 &#177; 0.14 m, p &lt; 0.005). KA was significantly lower on the VR360 treadmill, forcing a more knock-kneed walking position (TT:174.2 &#177; 3.9 vs VR:139.9 degrees, p &lt; 0.005) The 360 treadmill induced a bent over position, causing a significantly greater tilt (TT:175.8 &#177; 3.0 vs VR:156.5, p &lt; 0.005). CONCLUSION: Walking on a virtual reality treadmill is more strenuous from a physiological and biomechanical perspective than a traditional treadmill, at a self-selected and forced pace. Shorter exercise bouts using virtual reality treadmills may be a more practical use of this exercise modality.

A Reliability Comparison of Different Methods for Detecting Step Rate and Foot Strike Pattern in Runners Using Two-dimensional Video

Two-dimensional (2D) video is often used to evaluate running gait. Cost effective and clinically applicable methods have not been validated. The objective of this study was to evaluate the concurrent validity and agreement of methods used to determine step rate (SR) and foot strike pattern (FSP) during running using 2D video. We observed excellent agreement assessing SR from a 30 Hertz (Hz) video for 10 seconds (s) and multiplying it by 6. We observed excellent interrater agreement assessing FSP for 10s at 240 Hz. These 10s methods for assessing running may be used to inform clinical decision making when evaluating running gait. Key point's Two-dimensional video assessment at 30 Hz demonstrated high intra- and interrater reliability for detecting step rate; the 10-second method is valid and reliable for detecting step rate when compared to the 60-second method; Detecting foot strike using a 2-point scale is more reliable at 240Hz rather than 30Hz.

Oxygen uptake and muscle activity limitations during stepping on a stair machine at three different climbing speeds

This laboratory study examined human stair ascending capacity and constraining factors including legs’ local muscle fatigue (LMF) and cardiorespiratory capacity. Twenty-five healthy volunteers, with mean age 35.3 years, maximal oxygen uptake (VO2max) of 46.7 mL·min−1·kg−1 and maximal heart rate (HR) of 190 bpm, ascended on a stair machine at 60 and 75% (3 min each) and 90% of VO2max (5 min or until exhaustion). The VO2, maximal heart rate (HRmax) and electromyography (EMG) of the leg muscles were measured. The average VO2highest reached 43.9 mL·min−1·kg−1, and HRhighest peaked at 185 bpm at 90% of VO2max step rate (SR). EMG amplitudes significantly increased at all three levels, p < .05, and median frequencies decreased mostly at 90% of VO2max SR evidencing leg LMF. Muscle activity interpretation squares were developed and effectively used to observe changes over time, confirming LMF. The combined effects of LMF and cardiorespiratory constraints reduced ascending tolerance and constrained the duration to 4.32 min.Practitioner Summary: To expedite ascending evacuation from high-rise buildings and deep underground structures, it is necessary to consider human physical load. This study investigated the limiting physiological factors and muscle activity rate changes (MARC) used in the muscle activity interpretation squares (MAIS) to evaluate leg local muscle fatigue (LMF). LMF and cardiorespiratory capacity significantly constrain human stair ascending capacities at high, constant step rates.

Synchronizing Foot Strike and Cardiac Cycle Phase Affects Heart Rate and Metabolic Responses to Running

The interplay between physiological factors such as muscle perfusion and venous return to the heart has a major role in cardiovascular and peripheral responses during running. Timing cardiac contraction (i.e. systole) to occur in synchrony with skeletal muscle relaxation (swing phase of the gait cycle) may reduce cardiac afterload and promote coronary and skeletal muscle perfusion. In turn, this should manifest in a reduced HR response at a constant running velocity, secondary to an increased stroke volume. PURPOSE: To assess HR and metabolic responses associated with running when foot strikes are timed to occur during 1) the systolic phase of the cardiac cycle, or 2) the diastolic phase. METHODS: Ten elite male distance runners performed a testing session on the treadmill at 4.72 m/s (5:40 min/mile) pace while matching their steps to an auditory tone and wearing a chest strap that generated accelerometer and ECG signals. Testing began with a 3-min control stage (no tone), immediately followed by 2 or 3 pairs of “toned” stepping phases (pair = 2 x 3-min), where the signal to step was given either at 100% of the subject’s R-R interval (systolic stepping; SS) or 45% of R-R (diastolic stepping; DS). The order of DS and SS within each pair was randomized and double blinded. VO2, VE and RER were measured continuously. RESULTS: Twenty-eight pairs of DS + SS were used for HR, step rate (SR) and length (SL) comparisons and 24 pairs were included in metabolic data analyses. All subjects accurately timed their steps with the auditory tones (DS: 45.0 ± 4.3 %; SS: 100.1 ± 5.0 % of R-R interval). While VO2 was similar, HR, SR, VE and RER were significantly (p < 0.001) lower during DS compared to SS (HR: 172 ± 6 vs 175 ± 7 beats·min-1; SR: 172 ± 6 vs 175 ± 7 steps·min-1; VE: 100.0 ± 10.8 vs 103.7 ± 11.8 l·min-1; RER: 0.93 ± 0.03 vs 0.95 ± 0.03, for DS & SS, respectively) despite subjects having to lengthen their steps more during DS compared to SS (p < 0.001; 2.5 ± 3.1 vs 0.9 ± 3.2 % of control SL, respectively) to match HR. CONCLUSION: Synchronizing foot strike to occur during diastole, as opposed to systole, reduces HR during running, presumably as a result of an increase in stroke volume and/or enhanced muscle perfusion. The cardiac advantage with DS may be beneficial to distance running performance. Supported by a grant from Pulson Inc.

Effect Of Step Rate On Foot Strike Pattern And Running Economy In Novice Runners

Purpose—The objective was to examine if step rates ±5% or ±10% of a novice runner's preferred step rate (SR) is sufficient enough to shift a novice runner’s foot strike pattern (FSP) (rear-foot, mid-foot, forefoot) and whether these SR changes produce changes in the rate of submaximal oxygen consumption (VO2). Methods—Foot strike angle (FSA) was recorded using sagittal plane video images and VO2 was measured for novice runners while running on a treadmill at a constant speed during increased and decreased (±5% and ±10%) SR conditions. Foot strike angle was used to predict strike index (SI) (predicted strike index = [FSA – 27.4]/-0.39) and quantify FSP in each SR condition. Results—Predicted SI was significantly different between preferred SR and the -5% (p = .014), -10% (p = .001), and the +10% (p = .007) SR conditions. There was a shift to higher predicted SI measures in the increased SR conditions and lower predicted SI measures in the decreased SR conditions. Oxygen consumption was significantly increased in the -5% and -10% SR conditions (p =.000 and p = .003, respectively). Conclusion-Manipulations of SR produce shifts in FSP in novice runners and these changes cause small changes in submaximal VO2. EFFECTS OF STEP RATE ON FOOT STRIKE PATTERN 3

The impact of a long training run on muscle damage and running economy in runners training for a marathon

The purposes of this study were to evaluate whether there were changes in markers of cardiovascular and muscle damage and then to determine whether running economy (RE) was adversely affected due to those changes in a group of runners training for a marathon following a 26-km moderately paced outdoor long training run (LTR). Fifteen, healthy male participants (age: 35.2 ± 11.1 years; height = 171.2 ± 14.5 cm; body mass = 73.6 ± 11.9 kg; and VO2max = 63.6 ± 12.7 mL/kg/minute) completed the protocol. The LTR consisted of a 26-km run on a marked outdoor course with water stops and heart rate (HR) and rating of perceived exertion checkpoints every 5 km. Muscle damage [serum creatine kinase (CK)], delayed onset muscle soreness (DOMS), cardiorespiratory measures (HR, pulmonary ventilation, respiratory exchange ratio), muscle power, step rate (SR), and RE (oxygen consumption during treadmill running at 3.1, 3.6, and 4.0 m/second) were assessed before and 24, 48, and 72 hours after exercise. A repeated-measures analysis of variance showed that serum CK levels were significantly elevated at 24, 48, and 72 hours (145%, 112%, and 72% increase above baseline, respectively; p < 0.05). However, these significant increases in serum CK were not associated with an increase in DOMS. In addition, none of the RE measures or other dependent variables showed changes during the study. It was concluded that the muscle damage caused by a 26-km LTR was not reflected by changes in RE at submaximal speeds. Therefore, an LTR of this duration and intensity can be well tolerated in participants training for a marathon and routine training can be followed in the days after this run with few adverse consequences.

Sensitivity investigation of high resolution capillary zone electrophoresis for serum proteins (CZE-HR SPE) for slight monoclonal bands as compared to Hevylite™

The purposes of this study were to evaluate whether there were changes in markers of cardiovascular and muscle damage and then to determine whether running economy (RE) was adversely affected due to those changes in a group of runners training for a marathon following a 26-km moderately paced outdoor long training run (LTR). Fifteen, healthy male participants (age: 35.2 ± 11.1 years; height = 171.2 ± 14.5 cm; body mass = 73.6 ± 11.9 kg; and VO2max = 63.6 ± 12.7 mL/kg/minute) completed the protocol. The LTR consisted of a 26-km run on a marked outdoor course with water stops and heart rate (HR) and rating of perceived exertion checkpoints every 5 km. Muscle damage [serum creatine kinase (CK)], delayed onset muscle soreness (DOMS), cardiorespiratory measures (HR, pulmonary ventilation, respiratory exchange ratio), muscle power, step rate (SR), and RE (oxygen consumption during treadmill running at 3.1, 3.6, and 4.0 m/second) were assessed before and 24, 48, and 72 hours after exercise. A repeated-measures analysis of variance showed that serum CK levels were significantly elevated at 24, 48, and 72 hours (145%, 112%, and 72% increase above baseline, respectively; p < 0.05). However, these significant increases in serum CK were not associated with an increase in DOMS. In addition, none of the RE measures or other dependent variables showed changes during the study. It was concluded that the muscle damage caused by a 26-km LTR was not reflected by changes in RE at submaximal speeds. Therefore, an LTR of this duration and intensity can be well tolerated in participants training for a marathon and routine training can be followed in the days after this run with few adverse consequences.

THE EFFECTS OF COMBINED UPHILL-DOWNHILL SPRINT TRAINING ON BIOMECHANICAL VARIABLES

1467 The aims of the present study were to assess the efficacy of a novel combined uphill-horizontal-downhill sprint training method and its effects on the kinematic characteristics of sprinting running and on a battery of vertical jumps. Twenty-seven male physical education students comprised the two experimental (A and B) and one control (C) groups of the study. Groups A and B sprinted maximally with the same intensity and volume of exercise (3 times a week) over an 8-week period. The training programme consisted of 6 repetitions of 80 m sprints until the 4th week after which 1 repetition was added for each of the remaining weeks where the recovery periods between the repetitions were 4-6 min. Group A was trained on a uphill-downhill platform,(80 m long, 10 m flat, 20 m uphill at 3 ° slope, 10 m flat, 20 m downhill at 3 ° slope and 20 m flat) and Group B was trained on the horizontal. Pre and post training tests were employed to measure the effects of training on maximal step velocity (MSV), step rate (SR) and step length (SL), contact time(CT) and flight time (FT), as well as to a battery of vertical jumps. Only Group A increased MSV, significantly with training by 4.6% (8.05 ± 0.68 to 8.43 ± 0.69 m.s-1P<0.01), which was mainly due to an increase of SR by 4.6% (3.90 ± 0.29 to 4.09 ± 0.30 Hz, P<0.05). For the battery of vertical jumps the only noteworthy change was that for the 50 cm drop jump which was improved by 2.2% but not statistically significant. The findings of the present study suggest that this novel combined uphill-horizontal-downhill training method produced a significant improvement in performance compared to the same running performed on horizontal.