rmiller
11-17-2011, 04:35 PM
Hi everyone,
I was talking with some colleagues lately about a topic that I thought might be of interest to the board, and would love to hear the thoughts / opinions of others.
The metabolic cost ("cost of transport", CoT, the metabolic energy consumed per unit distance traveled) for human running was classically reported by Margaria et al. (1963) as being invariant with respect to the speed of progression. That study had a grand total of two subjects, but it seems to me that there's a general belief that unlike walking, running has no "energetically optimal" speed. The CoT is clearly less sensitive to speed for running than for walking, but later and more recent studies have suggested that the CoT is probably not entirely independent of running speed (e.g. Mayhew, 1977; Steudel-Numbers & Wall-Scheffler, 2009). Sometimes the CoT even appears to decrease slightly with increasing speed (e.g. see recent data from Ferris & Sawicki, 2011). It seems that large amounts of data, perhaps collected over multiple repeated sessions on different days, are needed to detect nonlinearity in the CoT-speed relationship for running (Steudel-Numbers & Wall-Scheffler, 2009).
My question is whether the measurements we take for calculating the CoT are really capturing the full metabolic energy consumption for a movement like running. As speed increases, I would expect that anaerobic metabolism starts to come into play, which the pulmonary gas-exchange-based measurements that we typically take to calculate energy expenditure in locomotion don't account for. It seems like the true CoT-speed relationship for running could be more nonlinear than we give it credit for, if we aren't accurately measuring the energy cost at faster speeds. I'm not aware of any energy-speed studies for running that have addressed this issue.
Is it well known (or even vaguely known) what the proportional contributions of aerobic and anaerobic metabolism are to the total energy expenditure as speed increases? Are there ways of accurately measuring anaerobic energy expenditure that can be reconciled with the typical cart-based measurements for aerobic energy expenditure (i.e. producing the joules of metabolic energy consumed anaerobically)? I found some studies using the "accumulated oxygen deficit" method to quantify the anaerobic contribution. Is this a generally accepted and valid metric for anaerobic energy expenditure?
Ross
I was talking with some colleagues lately about a topic that I thought might be of interest to the board, and would love to hear the thoughts / opinions of others.
The metabolic cost ("cost of transport", CoT, the metabolic energy consumed per unit distance traveled) for human running was classically reported by Margaria et al. (1963) as being invariant with respect to the speed of progression. That study had a grand total of two subjects, but it seems to me that there's a general belief that unlike walking, running has no "energetically optimal" speed. The CoT is clearly less sensitive to speed for running than for walking, but later and more recent studies have suggested that the CoT is probably not entirely independent of running speed (e.g. Mayhew, 1977; Steudel-Numbers & Wall-Scheffler, 2009). Sometimes the CoT even appears to decrease slightly with increasing speed (e.g. see recent data from Ferris & Sawicki, 2011). It seems that large amounts of data, perhaps collected over multiple repeated sessions on different days, are needed to detect nonlinearity in the CoT-speed relationship for running (Steudel-Numbers & Wall-Scheffler, 2009).
My question is whether the measurements we take for calculating the CoT are really capturing the full metabolic energy consumption for a movement like running. As speed increases, I would expect that anaerobic metabolism starts to come into play, which the pulmonary gas-exchange-based measurements that we typically take to calculate energy expenditure in locomotion don't account for. It seems like the true CoT-speed relationship for running could be more nonlinear than we give it credit for, if we aren't accurately measuring the energy cost at faster speeds. I'm not aware of any energy-speed studies for running that have addressed this issue.
Is it well known (or even vaguely known) what the proportional contributions of aerobic and anaerobic metabolism are to the total energy expenditure as speed increases? Are there ways of accurately measuring anaerobic energy expenditure that can be reconciled with the typical cart-based measurements for aerobic energy expenditure (i.e. producing the joules of metabolic energy consumed anaerobically)? I found some studies using the "accumulated oxygen deficit" method to quantify the anaerobic contribution. Is this a generally accepted and valid metric for anaerobic energy expenditure?
Ross