Mechanical determinants of gradient walking energetics in man.

Minetti, Alberto E.; Ardigò, Luca Paolo; Saibene, F.

doi:10.1113/jphysiol.1993.sp019969

Cited by 147 publications

(208 citation statements)

References 18 publications

(17 reference statements)

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“…As mentioned earlier, the trajectory of the centre of mass is monotonically ascending (or descending) at that steepness (Minetti et al 1993). Thus, potential energy change is the predominant component of the external work and is likely to be the same in both groups.…”

Section: K1mentioning

confidence: 73%

“…Five porters and five Caucasians (71.2G11.1 kg, 1.73G0.05 m, 31.2G5.8 years, four of which were professional/expert mountaineers) were asked to ascend and descend 22% steep paths (482 and 325 m long, respectively, in the two locations) loaded with 25, 45 and 60 kg in their doko/rucksack, at a speed they could maintain for several hours. The paths were chosen in order to make sure that the trajectory of the body centre of mass was monotonically increasing or decreasing and no pendulum-like strategy could be adopted within the step (Minetti et al 1993). In this way, the mechanical power is prevalently determined by the rate of change of potential energy (see §1).…”

Section: Methodsmentioning

confidence: 99%

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Himalayan porter's specialization: metabolic power, economy, efficiency and skill

2006

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Carrying heavy loads in the Himalayan region is a real challenge. Porters face extreme ranges in terrain condition, path steepness, altitude hypoxia and climate for 6-8 h a day, many months a year, since they were boys. It has been previously shown that, when carrying loads on level terrain, porters' metabolic economy is higher than in Caucasians but the reasons are still unknown. We monitored Nepalese porters both during 90 km trekking in Khumbu Valley and at two different altitudes (3490 and 5050 m above sealevel), where they were compared to Caucasian mountaineers during (22%) gradient walking. Both subject groups carried a load of up to 90% body mass. The remarkably higher performance of porters during uphill locomotion (C60% in speed, C39% mechanical power) is only partly explained by the lower cost of loaded walking (K20%), being also the result of a better cardio-circulatory adaptation to altitude, which generates a higher mass-specific metabolic power (C30%). Consequently, Nepalese porters show higher efficiency, both during uphill and downhill loaded walking. Their higher economy on steep paths cannot be ascribed to a better exchange between potential and kinetic energy, as in our experiments the body centre of mass travelled monotonically uphill (or downhill). A different oscillation pattern of the loaded head-trunk segment, together with the analysis of the different components of the mechanical work during load carrying, suggests that achieved motor skills in balancing the loaded body segment above the hip could play a role in determining the better economy of porters.

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Section: K1mentioning

confidence: 73%

Section: Methodsmentioning

confidence: 99%

Himalayan porter's specialization: metabolic power, economy, efficiency and skill

2006

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“…It is well known that the metabolic cost of eccentric muscle actions is much less than that of concentric contractions (Asmussen 1953;BiglandRitchie and Woods 1976;Rall 1985). As Minetti et al (1993) showed, a change in the relative contribution of concentric and eccentric muscle actions, combined with the difference in metabolic costs between both muscle actions will lead to very small increases in the metabolic cost for running up shallow inclines. Consequently, for running up shallow inclines, as used in the present study, the D efficiency will be much greater than the concentric muscle efficiency.…”

Section: Discussionmentioning

confidence: 99%

Differences in leg muscle activity during running and cycling in humans

Bijker

Groot

Hollander

2002

European Journal of Applied Physiology

116

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Delta (D) efficiency is defined as the ratio of an increment in the external mechanical power output to the increase in metabolic power required to produce it. The purpose of the present study was to investigate whether differences in leg muscle activity between running and cycling can explain the observed difference in D efficiency between the two activities. A group of 11 subjects performed incremental submaximal running and cycling tests on successive days. The D efficiencies during running and cycling were based on five exercise stages. Electromyograph (EMG) measurements were made of three leg muscles (gastrocnemius, vastus lateralis and biceps femoris). Kendall's correlation coefficients between the mean EMG activity and the load applied were calculated for each muscle, for both running and cycling. As expected, the mean D efficiency during running (42%) was significantly greater than that during cycling (25%). For cycling, all muscles showed a significant correlation between mean EMG activity and the load applied. For running, however, only the gastrocnemius muscle showed a significant, but low correlation (r=0.33). The correlation coefficients of the vastus lateralis and biceps femoris muscles were not significantly different from 0. The results were interpreted as follows. In contrast to cycling, which includes only concentric contractions, during running up inclines eccentric muscle actions play an important role. With steeper inclines, more concentric contractions must be produced to overcome the external force, whereas the amount of eccentric muscle actions decreases. This change in the relative contribution of concentric and eccentric muscle actions, in combination with the fact that eccentric muscle actions require much less metabolic energy than concentric contractions, can explain the difference between the running and cycling D efficiency.

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“…Surface compliance and damping can affect locomotion energetics and dynamics (Ferris et al, 1998;Ferris et al, 1999;Kerdok et al, 2002), as do surface inclines or declines (Margaria, 1976;Minetti et al, 1993). However, few studies have characterized the biomechanics and energetics of walking on uneven surfaces.…”

Section: Discussionmentioning

confidence: 99%

Biomechanics and energetics of walking on uneven terrain

Voloshina

Kuo

Daley

et al. 2013

Journal of Experimental Biology

204

186

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Summary Walking on uneven terrain is more energetically costly than walking on smooth ground, but the biomechanical factors that contribute to this increase are unknown. To identify possible factors, we constructed an uneven terrain treadmill that allowed us to record biomechanical, electromyographic, and metabolic energetics data from human subjects. We hypothesized that walking on uneven terrain would increase step width and length variability, joint mechanical work, and muscle co-activation compared to walking on smooth terrain. We tested healthy subjects (N=11) walking at 1.0 m/s, and found that, when walking on uneven terrain with up to 2.5 cm variation, subjects decreased their step length by 4% and did not significantly change their step width, while both step length and width variability increased significantly (22% and 36%, respectively; p<0.05). Uneven terrain walking caused a 28% and 62% increase in positive knee and hip work, and a 26% greater magnitude of negative knee work (0.0106, 0.1078, and 0.0425 J/kg, respectively; p<0.05). Mean muscle activity increased in seven muscles in the lower leg and thigh (p<0.05). These changes caused overall net metabolic energy expenditure to increase by 0.73 W/kg (28%; p<0.0001). Much of that increase could be explained by the increased mechanical work observed at the knee and hip. Greater muscle co-activation could also contribute to increased energetic cost but to unknown degree. The findings provide insight into how lower limb muscles are used differently for natural terrain compared to laboratory conditions.

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Mechanical determinants of gradient walking energetics in man.

Cited by 147 publications

References 18 publications

Himalayan porter's specialization: metabolic power, economy, efficiency and skill

Himalayan porter's specialization: metabolic power, economy, efficiency and skill

Differences in leg muscle activity during running and cycling in humans

Biomechanics and energetics of walking on uneven terrain

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