Abstract
INTRODUCTION
Many subjective factors can affect energy cost (V’O2max, [7]; maximal strength and flexibility, [3]) and
mechanical work (stride frequency, [6]) of walking. To our knowledge, no studies have been conducted to
investigate if the level of daily physical activity (PAL) can affect external mechanical work (WEXT) and net
energy cost (NetEC) of treadmill walking. The aim of the study was to analyse the relation between NetEC and
WEXT with PAL.
2. MATERIALS AND METHODS
20 healthy adults were recruited in the study and were classified as inactive (INACT) and active (ACT)
according to the amount of daily moderate and vigorous physical activity (MVPA). Main characteristics are
summarized in Table 1.
NetEC (obtained from GrossEC– Standing metabolic rate) was analysed with indirect calorimetry (K4b2,
Cosmed, Italy) and simultaneously, a kinematic analysis was performed with an optoelectronic system
(SMART-E, BTS, Italy) to calculate WEXT during 3 bouts of treadmill walking of 10 min each at 0.97/1.25/1.53
m/s. To assess PAL, subjects wore an activity monitor (Actiheart, CamNtech, UK) for a whole week, inferring
time spent in sedentary (SED, <1.5 METs), or moderate to vigorous (MVPA, >3 METs) physical activity.
Statistical Analysis: One-way ANOVA was performed to evaluate differences between ACT and INACT. A
repeated measure ANOVA (2x3) was used to determine differences between velocities. An ANCOVA
analysis was made to find out associations between NetEC and WEXT with PAL. The correlation analysis was
performed to investigate relationships between variables. Significance was set at p<0.05.
3. RESULTS
When compared with INACT, ACT had a significantly higher amount of MVPA (P<0,0001). No group
differences were observed for SED behaviour (Table 2).NetEC increased significantly at all velocities, except for speed from 0.97 to 1.25 m/s. On the contrary, WEXT
decreased significantly when velocities grow up, excluding speed from 1.25 to 1.53 m/s (Fig.1-2).No significant associations were found between MVPA or SED with neither NetEC nor WEXT. Significant
correlations between NetEC or WEXT calculated at the different speeds were found (r>0.583; p<0.01; Table 3).DISCUSSION
Our data indicate that ACT and INACT adults differ for MVPA but not for SED patterns. For both groups it is
extremely important to reduce SED behaviour regardless of performed activities in order to prevent
cardiovascular diseases [1]. It is well established that a U-shaped relationship between NetEC and walking
speed exists [4]. Our values are substantially in agreement with literature [5;8], even if the U-shaped trend is
not visible, probably due to the different number of tested speeds (we have only 3 speeds vs. 4-6 of literature).
In addition, different treadmills, metabolic charts and ways to calculate resting metabolic rate may partially
explain the variability in the trends. Reference [2] showed that WEXT reaches a minimum at a speed near the
preferred walking speed: before and after this threshold, WEXT increases. The absence of significance between
1.25 and 1.53 m/s indicates that our minimum value may be positioned around these speeds. Probably, adding a
higher velocity, closer to the preferred walking speed of our subjects, an increase in the values will appear. The
absence of associations may be explained by a small sample size and speeds eliciting a V’O2 corresponding to
very light/ light activity intensities [1]. Significant correlations between NetEC or WEXT at the three different
speeds suggest that subjects motor patterns during walking persist even with increasing speeds.
In conclusion, neither SED nor MVPA seem to influence NetEC and WEXT of light intensity treadmill walking
in a healthy adult population.
5. REFERENCES
[1] American College of Sports Medicine, 2011. Quantity and quality of exercise for developing and
maintaining cardiorespiratory, musculoskele
Lingua originale | English |
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Titolo della pubblicazione ospite | Book of Abstracts |
Pagine | 210-212 |
Numero di pagine | 3 |
Stato di pubblicazione | Pubblicato - 2012 |
Evento | XII International Symposium
on 3D Analysis of Human Movement
Technology & Treatment - Bologna Durata: 18 lug 2012 → 20 lug 2012 |
Convegno
Convegno | XII International Symposium on 3D Analysis of Human Movement Technology & Treatment |
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Città | Bologna |
Periodo | 18/7/12 → 20/7/12 |
Keywords
- Treadmill Walking
- energy cost
- external mechanical work
- physical activity level