Luca P. Ardigò

Metabolic cost, mechanical work, and efficiency during walking in young and older men

Aim:u2002 To investigate mechanical work, efficiency, and antagonist muscle co‐activation with a view to better understand the cause of the elevated metabolic cost of walking (CW) in older adults.

Gastrocnemius muscle–tendon behaviour during walking in young and older adults

Aim:u2002 Age‐related differences in muscle architectural and tendon mechanical properties have been observed in vivo under static conditions and during single joint contractions. The aim of this study was to determine if there are age‐related differences in gastrocnemius fascicle–tendon interactions during a fundamental locomotor task – walking.

Effect of a 12-month physical conditioning programme on the metabolic cost of walking in healthy older adults.

The metabolic cost of walking (CW) is increased in healthy older adults. Previously, this has been suggested to be associated with age-related decline in physiological/functional factors such as stability and muscle size and strength. Physical training can improve such factors as well as aspects of gait performance in older adults. The aim of this investigation was to determine if it also has a beneficial impact on (lowers) CW. Thirty-eight community dwelling older adults (aged 70–82xa0years) assigned to a training group (TRA, n=25) or a control group (CON, n=13) participated in a 12-month intervention. TRA followed a multi-component physical conditioning programme involving supervised resistance, aerobic, and balance exercises twice per week. They also undertook home based exercises once per week. CON carried on with their normal daily activities. CW and indicators of functional capacity (knee extensor isometric strength, single leg balance time, sit and reach, stand and reach, and 6xa0min walk distance) were assessed prior to and following the intervention. Significant improvements in knee extensor isometric strength (+21%), single leg balance time (+30%), and 6xa0min walk distance (+6%) were observed in TRA (P<0.05) but not in CON. However, no change in CW was observed. In conclusion, this investigation has shown that a multi-component physical conditioning programme had a beneficial impact on functional capacity but did not lower CW in healthy community dwelling older adults.

The optimal locomotion on gradients: walking, running or cycling?

On level ground, cycling is more economical than running, which in turn is more economical than walking in the high speed range. This paper investigates whether this ranking still holds when moving on a gradient, where the three modes are expected to be mainly facing the same burden, i.e. to counter gravity. By using data from the literature we have built a theoretical framework to predict the optimal mode as a function of the gradient. Cycling was found to be the mode of choice only below 10–15% gradient, while above it walking was the least expensive locomotion type. Seven amateur bikers were then asked to walk, run and ride on a treadmill at different gradients. The speed was set so as to maintain almost constant the metabolic demand across the different gradients. The results indicate that the critical slope, i.e. the one above which walking is less expensive than cycling (and running), is about 13–15%. One subject was loaded during bipedal gaits with a bicycle-equivalent mass, to simulate to cross-country cycling situation. The critical slope was close to 20%, due to the higher metabolic cost of loaded walking and running. Part of the findings can be explained by the mechanically different paradigms of the three locomotion types.

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

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 6–8u200ah 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 90u200akm trekking in Khumbu Valley and at two different altitudes (3490 and 5050u200am above sea-level), 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 (+60% in speed, +39% mechanical power) is only partly explained by the lower cost of loaded walking (−20%), being also the result of a better cardio-circulatory adaptation to altitude, which generates a higher mass-specific metabolic power (+30%). 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.

Biomechanics: Halteres used in ancient Olympic long jump

Halteres (αλτηρεζ) are hand-held weights that were first used in the standing long jump in the eighteenth ancient Olympiad in 708 bc, and may have been introduced either to make the challenge more difficult or to extend the jumping distance. Here we use computer and experimental simulations to determine the optimal mass of halteres that would be needed to maximally extend a standing long jump, and find that this corresponds closely to the size range of actual archaeological specimens. These halteres were made of stone or lead and weighed 2–9 kg, which we calculate would increase a 3-metre jump by at least 17 cm, indicating that their purpose was to boost the performance of pentathletes. Halteres may therefore be the earliest passive tool that was devised to enhance human-powered locomotion.

Human locomotion on snow: determinants of economy and speed of skiing across the ages

We explore here the evolution of skiing locomotion in the last few thousand years by investigating how humans adapted to move effectively in lands where a cover of snow, for several months every year, prevented them from travelling as on dry ground. Following historical research, we identified the sets of skis corresponding to the ‘milestones’ of skiing evolution in terms of ingenuity and technology, built replicas of them and measured the metabolic energy associated to their use in a climate-controlled ski tunnel. Six sets of skis were tested, covering a span from 542 AD to date. Our results show that: (i) the history of skiing is associated with a progressive decrease in the metabolic cost of transport, (ii) it is possible today to travel at twice the speed of ancient times using the same amount of metabolic power and (iii) the cost of transport is speed-independent for each ski model, as during running. By combining this finding with the relationship between time of exhaustion and the sustainable fraction of metabolic power, a prediction of the maximum skiing speed according to the distance travelled is provided for all past epochs, including two legendary historical journeys (1206 and 1520 AD) on snow. Our research shows that the performances in races originating from them (Birkebeiner and Vasaloppet) and those of other modern competitions (skating versus classical techniques) are well predicted by the evolution of skiing economy. Mechanical determinants of the measured progression in economy are also discussed in the paper.

The transmission efficiency of backward walking at different gradients.

Abstract. The specialized design of the bipedal system towards forward locomotion has been assessed by measuring the metabolic cost and the mechanical work of both forward and backward walking on a treadmill at seven gradients from 0 to +32%. With respect to forward locomotion, backward walking implies: (1) a higher metabolic cost particularly at level gradient, while at steeper inclines the difference decreases, (2) the same mechanical internal work despite an increased stride frequency, (3) higher mechanical external work within a gradient range from 0 to +15%, (4) lower energy recovery, i.e. the ability to save mechanical energy by moving as an inverted pendulum, mainly in level walking, and (5) as a consequence of the above results, a decrease of the efficiency of locomotion particularly at the 0% gradient. The transmission efficiency of backward walking, relative to the forward progression, was found to be about 65% in level locomotion, while at higher gradients it increased to and was maintained at a value of about 93%. The poorer economy of level backward walking could also be explained by an impaired elastic contribution in the last part of the double contact phase, while the similarity of the two gaits on higher gradients is caused by disruption of the pendulum-like paradigm due to the trajectory geometry of the bodys centre of mass progressively losing its downward portion.