Energetics of human locomotion near the walk-run transition speed.

Energetics of human locomotion near the walk-run transition speed.

 

This dataset includes the raw metabolic and mechanical  data of 28 young subjects during locomotion at variable speed, walking and running on a treadmill at different speeds and gaits.

Characteristics of the experimental group:

- Sex: 28 Males - Age: 32. 53 (10.99SD)- height: 175.0 cm (0.008 SD)- weight: 72.96 kg (9.51 SD)

Equipment:

- Cosmed K5 portable metabolic analyzer- Cosmed Omnia Software v.1.6.5

- Vicon Nexus 2.14 (Vicon Motion Systems Ltd, Oxford, UK)

Experimental Design: The walking stroke transition speed (W-R Ts) was determined experimentally. Each subject was asked to perform 3 trials on a treadmill (GE T2100, General Electric, USA), with an escalating speed ladder protocol. The ramp was designed to start with a comfortable ride (3.0 km h-1), and to increase speed by 0.5 km.h-1 every 15 s. When the subject began to run, the ramp stopped and the speed was marked on a worksheet. The mean or modal transition speed was taken as the T of the subject. All treadmill tests were performed at the Biomechanics and Motion Analysis Research Laboratory (LIBiAM) of the University of the Republic in Paysandú (Uruguay), at a controlled temperature of 25ºC.

The theoretical transition velocity tTs was calculated according to the Froude number equation (Alexander. 1976): v = (nFr g LL) 0.5, where v is the theoretical velocity, g is gravity, LL is the leg length, and nFr the Froude number, which was set to the constant value of 0.5,  corresponding to the W-R transition (Alexander & Jayes, 1983; Alejandro, 2003; Bona et al., 2019).

Experimental speed ramp:

-A custom ascending and descending speed ramp was designed, focused on the transition speed and varied from (Ts = Transition Speed) Ts-20% to Ts+20%, each step with a duration of 5 s. Each ramp cycle lasted 50 s, and was repeated 5 times, for a total test time of 250 s. The trial was repeated twice.

 

Mechanical Work (Mechanical cost of transport)

The time course of the trajectory by BcoM was used to infer changes in the mechanical energies (potential and kinetics) involved. The horizontal work (W_h) was defined as the sum of the increments of the kinetic energy of the BcoM along the forward and mediolateral axes; the vertical work (W_v) was determined by the sum of the increments of gravitational potential energy and kinetic energy along the vertical axis; the external work (W_ext ), the mechanical work done to lift and accelerate the BcoM, was computed as the sum of the increments of the total mechanical energy of the BcoM (potential plus kinetic) (Cavagna et al., 1976; Willems et al., 1995). The internal work (W_int), the work necessary to accelerate the body segments with respects to the BcoM, was estimated with the methodology proposed by Cavagna & Kaneko (1977).  W_int and W_ext were summed to give the total mechanical work (W_tot) (Cavagna & Kaneko, 1977; Willems et al., 1995). 

During locomotion cycles, especially in W, part of the potential energy of the BcoM is converted into kinetic energy, and vice versa, so that the sum of W_h and W_v is greater than the actual work done (W_ext). The difference, expressed as percentage, corresponds to the energy recovery R% (Cavagna et al., 1976), which formula is:

R% = (W_h + Wv - W_ext) (W_h + Wv)

 Cost of transport (Metabolic transport cost)

Oxygen uptake and respiratory quotient were measured breath-by-breath by a portable metabolimeter (K5, Cosmed, Italy). Reference resting values were measured during 5 min in orthostatic quiet position. Each trial was started when the metabolic parameters were near the reference resting values.

The ₂ (mlO₂.kg^-1.min^-1) and RQ of the last 50 s of each recorded trial, corresponding to the last complete ramp, were averaged. The reference resting ₂ was subtracted to the measured one to obtain the net oxygen uptake. VO_2NET was then converted to mass-specific metabolic rate (W kg^-1) using a RQ based energetic equivalent(P. E. Di Prampero et al., 2015). The C (J kg^-1 m^-1) was finally obtained by dividing the metabolic rate for the average speed:  

 

             (2)

 

Apparent Mechanical Efficiency (AE)

The AE was calculated as proposed by Cavagna and Kaneko, ie,

AE = W_to C

where W_tot is the total mechanical work and C the cost of transport (G. A. Cavagna & Kaneko, 1977).

 

Data processing and calculation

Image preprocessing was performed in Vicon Nexus 2.14 (Vicon Motion Systems Ltd, Oxford, UK), kinematic variable calculation performed with Python 2.7 and ProCalc 1.6 (Vicon Motion Systems Ltd, Oxford, UK), the calculation of mechanical variables was implemented in MatLab  (The MathWorks, Inc., California, USA). The calculation of C was performed in Microsoft Excel (Microsoft Office 365).

 

Note: Not all subjects performed the entire protocol. In particular, some data lack follow-up.

Analysis of the cost of transportation:

All participants signed an informed consent. The protocol was approved by the University's Ethics Committee (#311170-000921-19).
 

The legend of the dataset.

There are 3 excel sheets  where each row is associated with subjects from 1 to 28.

Energy sheet:

Subject: Subject

Age

Weigth

Heigth(m)

IMC

Km x week: kilometers per week

Background: history of injuries

INT1 km/h: attempt 1

INT2 km/h: attempt 2

INT3 km/h: Attempt 3

Average transition (km/h): average walk-race transition speed

Froude estimated PST(m/s)

Froude Estimated PST(km/h)

Basal Vo2: Basal oxygen consumption  in orthostasis

VO2/kg/min: Oxygen consumption in the test

RQ: RQ in the test

VO2 Net VO2kg/min): VO2 net in the test

VO2/kg/s

J/kg/s = W/kg

C (J/kg/m): transport cost obtained in the test

 

Test: test performed

Gait: type of gait that has been evaluated

ASC/DESC: place on the ramp (ascending or descending)

Stride: stride identification  for each type of gait

Duty Factor_tr: duty factor

Stride Frequency_tr: stride frequency

Stride Time_tr: stride time

Time: time in the stride

Speed in treadmill : speed that occurs in treadmill

Distance: distance traveled by the stride

Step frequency: frequency of passage

Wext: External Work

Rec: recovery

Wv: trabajo vertical

Wh: horizontal work

WintTOT: Total internal work