Dr.Biol., Professor  S.I. Loginov¹
PhD A.S. Kintyukhin¹
PhD, Associate Professor M.Ya. Braginsky¹
PhD, Associate Professor A.S. Snigirev^1
1Surgut State University, Surgut

Keywords: walking cadence, walking index, oxygen consumption, students.

Background. Walking is ranked high in the modern health physical education toolkit [2, 4] with its intensity classifiable as low (health-prioritizing practices) under 3 MET; moderate (physical fitness) 3 to 6 MET; and high (physical progress focused) above 6 MET [5]. However, the walking technique aspects including stride, rhythm and frequency – are not always clear enough. The latter two parameters are referred to herein as the walking cadence (steps/min) [6] that is automatically developed by every individual on a preferential basis.

Objective of the study was to profile the energy cost versus walking cadence ratios in the young population groups of the urbanized Yugra North.

Methods and structure of the study. We sampled for the study the Surgut State University students (n=37, aged 19.8±1.95 years, including 19 males and 18 females), each of them having no contraindications for the physical fitness tests, conditional on an informed written consent for the experiment. The sample was tested by a 30min stepped treadmill test rated at 2-7km/h on Matrix Treadmill system, with 5min work at every speed step to obtain the oxygen consumption (ml/min), respiration rate (RR, breaths/ min), specific oxygen consumption (SOC, ml/min/kg) and heart rate (HR, bpm); with the oxygen consumption and HR data averaged on a 15s basis and stored for analyses. The respiration, oxygen consumption and metabolic performance were rated by Fit mate Pro (COSMED, Italy) system. Steps were rated by GoPro Hero 6 Black video-camera at 120 frames/s to obtain the full step time (FST, s), mode amplitude ((MА, %), walking index (WI, points), stride (S, mm); plus we metered the leg length (m) and the body mass and length (kg, m). WI was computed using the formula WI = MA/(2 × Мо × dX), where Мо is the mode class, s; MA is the mode amplitude, %; dX is the variation range (minimal to maximal point interval), s. The test data were statistically processed using Statistica, v.10 (StatSoft, USA) software toolkit, with a prior rating of the distribution normality; followed by computations of a mean arithmetic value (X), standard deviation (SD), 0.95 confidence interval (± 0.95 CI), with the correlation and regression analyzes. Significance of the differences were rated by a two-sided t-test for related/ unrelated groups plus nonparametric Wilcoxon-Mann-Whitney test with the threshold rate of p≤0.05.

Results and discussion. The male subgroup was tested with the significantly higher body length, body mass and leg length rates than the peer female group (1.77±6.3m, 72.3±13.8kg, 0.90±0.06m versus 1.67±5.8 m, 59.2±7.9 kg, 0.83±0.03 m, respectively, p<0.05), with virtually no differences in ages (19.5±2.4 versus 20.1±1.5 years) and body mass indices (22.9±3.9kg/m2 versus 21.2±2.6kg/m2, respectively). We found significant growth of the oxygen consumption, HR and RR with the walking speed growth in the 5-plus km/h range: see Table 1.

Table 1. Varied-walking-speed treadmill tests: cardio-respiratory system functionality test rates

Note: ▲ gender difference significance rate for WS=2km/h; * gender difference significance rate of p≤0,05; (X±SD) – mean arithmetic value and standard deviation; RR – respiratory rate, breath/ min, HR heart rate, beats/ min, OC - oxygen consumption, ml/min; SOC - specific oxygen consumption, ml/kg/min

The stride timing and biomechanics were tested to change with the WS growth; with the full step time, step time mode, ground contact time and areal time tested to fall; and the mode amplitude, stride and walking index (WI)  tested to grow at 3 km/h and above (p<0.05): see Table 2. It should be emphasized that the WI further grows at walking speeds of 5-plus km/h as a result of the neuro-motor walking pace control mechanisms being activated, particularly in the female group.

Table 2. Varied-WS treadmill tests: walking technique test rates of the sample (X±SD), n=37

Note: FST full step time, s; WI walking index, points; MA mode amplitude, %; S stride, mm; GCT ground contact time, s; AT aerial time, s; * difference significance rate of p≤0,05 for 2 to 3-7 km/h WS range

Metabolic cost rates of a walking cadence were tested virtually gender-unspecific, with the men and women tested to make 92 and 96 steps/min at 3 МЕТ, and 142 and 143 steps/ min at 6 MET, respectively: see Figure. Note that the line crossing points indicate the 3 MET and 6 МЕТ levels; and the dashed lines indicate the 0.95 confidence interval.

Figure 1. Gender-specific energy cost (МЕТ) correlation with the walking cadence: A males, B females

The above test data may be analyzed by the following two procedures.

Analysis 1: We used metabolic equivalent (МЕТ) units to rate the energy costs of the walking cadence models recommended for the young Northern population, since MET is traditionally applied by the Western rehabilitation specialists, physicians and fitness trainers for the physical load rating purposes. Note that 1 MET equals 1 kcal per hour per 1 kg of body mass, an equivalent of the oxygen consumption of 3.5 ml/ minute per 1 kg of body mass. This means that the walking cadence of 3 or 6 MET claims 3 or 6 times higher basic metabolism, respectively. These units are convenient for the health-prioritizing physical trainings, particularly for the walking intensity rating purposes in the special health group trainings. As demonstrated by the Figure, the walking cadence may be rated at 96 and 92 steps/min to keep energy cost at 3 MET in the women and men group trainings, respectively.

Correlation of walking cadence with the energy cost may be expressed as follows: E = 3.31 - 0.044K + 0.004 К², where E is the energy cost (MET), K is the walking cadence (steps/ min); and 0.044 and 0.004 are the empirical coefficients. The equation may be used to convert the energy costs of 4/ 5 MET into the walking cadence (steps/ min) when necessary for the physical trainings of healthy students or for clinical rehabilitation purposes. It may be pertinent to mention that the health-prioritizing walking cadence of 142-143 steps/ min (6 MET) may unlikely be applicable to the Yugra North population – despite the fact that the energy costs of 3 to 6 MET are commonly ranked as medium-intense. A similar study of the 18-20 year-old group found that the walking cadence of 95.9 and 119.3 steps/ min claimed the energy costs of 3 and 6 MET, respectively [6]. We are going to analyze the walking energy costs versus the leg lengths, body masses and walking cadences in our upcoming study report.

Analysis 2: In addition to the optimal walking cadence rating in the metabolic equivalent units, we analyzed the stride variability versus the waking speeds using the integrated walking index (WI) that may be beneficial for analyses of the full stride timing parameters. Modal class may be defined as the class including the widest range of the recorded step intervals, with its mean value referred to as the mode (Mo, s) for the subject section of the video capture. Mode amplitude (MA) is found as the modal class intervals (in percentage terms) to the total intervals ratio.

The WI calculated by the above formula was found to grow with the walking speed growth from 2 to 7 km/h by 15.3 and 19.4 times in the men and women groups, respectively (see Table 2) that may be indicative of the significant stress of the control mechanisms. Walking controls appear to use the movement coordination, balancing and walking style adjusting nervous channels. A main locomotor pattern is known to be designed by the central patterns of the spinal cord [1] which are modulated by a sensory feedback in the spinal cord and, in case of severe disorders, corrected by motor cortical controls with additional muscle synergies being formed [3]. It is also not improbable that the WI generally refers to these complex neuro-motor control mechanisms regardless of their scenarios.

Conclusion. Based on the study data, we offer a population-group-specific physical activity index i.e. the walking cadence of 95/ 120 steps per min claiming the energy costs of 3/ 4 MET for men/ women groups, respectively. Walking indices of  609-1280 and 795-1381 points may be applied on the Yugra North to rate the individual responses to the walking-dominated physical trainings of the healthy men and women groups, respectively.

The study was sponsored by the Education and Youth Policy Department of the Khanty-Mansi Autonomous Yugra Territory under the State Project ‘New varied-intensity physical training and health technologies with the physical progress tests for the KMAT Yugra’.

References

1. McCrea D.A., Rybak I.A. Organization of mammalian locomotor rhythm and pattern generation. Brain Res. Rev. 2008. V. 57. P. 134–146.
2. Pearson M., Dieberg G., Smart N. Exercise as a therapy for improvement of walking ability in adults with multiple sclerosis: a meta-analysis. Arch. Phys. Med. Rehabil. 2015. V. 96. N 7. P. 1339-1348.e7. doi: 10.1016/j.apmr.2015.02.011.
3. Safavynia S.A., Ting L.H. Sensorimotor feedback based on task-relevant error robustly predicts temporal recruitment and multidirectional tuning of muscle synergies.  Neurophysiol. 2013. V.  109. N1. P. 31-45. doi: 10.1152/jn.00684.2012.
4. Tudor-Locke C., Han H., Aguiar E.J., Barreira T.V., Schuna J.M., Kang M., Rowe D.A. How fast is fast enough? Walking cadence (steps/min) as a practical estimate of intensity in adults: a narrative review.  Br. J. Sports. Med. 2018. V. 52. N 12. P. 776-788. doi: 10.1136/bjsports-2017-097628.
5. Tudor-Locke C., Schuna J.M., Han H., Aguiar E.J., Larrivee S., Hsia D.S., Ducharme S.W., Barreira T.V., Johnson W.D. Cadence (steps/min) and intensity during ambulation in 6-20 year olds: the CADENCE-kids study. Int. J. Behav. Nutr. Phys. Act. 2018. V. 15. N 1. 20. doi: 10.1186/s12966-018-0651-y.

Corresponding author: logsi@list.ru

Abstract

Walking is ranked high in the modern health physical education toolkit, with its intensity classifiable as low (health practices) under 3 MET; moderate 3 to 6 MET (physical fitness); and high above 6 MET (for physical progress). However, the walking technique aspects including the stride length, rhythm and frequency – are not always clear enough. The latter two parameters are referred to herein as the walking cadence (steps/min) [5] that is automatically developed by every individual depending on the preference. We sampled for the study the Surgut State University students (n=37, aged 19.8±1.95 years, including 18 females) to rate the walking cadence versus the metabolic cost within 3-6 MET range. The sample was tested by a stepped treadmill test at 2-7km/h, with 5min work at every speed step to obtain the oxygen consumption, respiration rate, heart rate, and pace parameters (full step time, mode amplitude, walking index, specific step time, support contact time and aerial time); plus anthropometric rates including the leg length, body length and body mass. The test rates were found to grow with the walking speed (t test, p <0.05). The energy demand (E, MET) to walking cadence (WC, step/min) ratio was found gender-unspecific as described by the following equation: E = 3.31-0.044WC + 0.004WC2, where E is the energy demand in MET, walking cadence is the walking cadence in steps/min; 0.044 and 0.004 are the empirical ratios (note: metabolic equivalent of physical activity, where 1 MET = 1.0 kcal/h/kg or 3.5 ml O2 /min/kg). The walking index was found to grow with the walking speed growth from 2 to 7 km/h 15.3 and 19.4 times for men and women, respectively – that is presumably indicative of the significant stress on the neuro-locomotor regulatory mechanisms. Based on the study data, we offer a population-group-specific physical activity index i.e. the walking cadence of 95/ 120 steps per min claiming the energy costs of 3/ 4 MET for men/ women groups, respectively. The walking cadence may be effectively used to rate physical progress in the walking practices of the Northern population groups.