Skiing across the Greenland icecap: divergent effects on limb muscle adaptations and substrate oxidation

Abstract

This study investigates the adaptive response of the lower limb muscles and substrate oxidation during submaximal arm or leg exercise after a crossing of the Greenland icecap on cross-country skies. Before and after the 42-day expedition, four male subjects performed cycle ergometer and arm-cranking exercise on two separate days. On each occasion, the subjects exercised at two submaximal loads (arm exercise, 45 W and 100 W; leg exercise, 100 W and 200 W). In addition, peak oxygen uptake (V . O∑max) was determined for both leg and arm exercise. Before and after the crossing, a muscle biopsy was obtained from the vastus lateralis and the triceps brachii muscles prior to exercise (N=3). After the crossing, body mass decreased by 5.7±0.5 kg (in four of four subjects), whereas V . O∑max was unchanged in the arm (3.1±0.2 l min -1 ) and leg (4.0±0.1 l min -1 ). Before the crossing, respiratory exchange ratio (RER) values were 0.84±0.02 and 0.96±0.02 during submaximal arm exercise and 0.82±0.02 and 0.91±0.01 during submaximal leg exercise at the low and high workloads, respectively. After the crossing, RER was lower (in three of four subjects) during arm exercise (0.74±0.02 and 0.81±0.01) but was higher (in three of four subjects) during leg exercise (0.92±0.02 and 0.96±0.01) at the low and high workloads, respectively. Citrate synthase and β-hydroxy-acyl-CoAdehydrogenase activity was decreased by approximately 29% in vastus lateralis muscle and was unchanged in triceps brachii muscle. Fat oxidation during submaximal arm exercise was enhanced without a concomitant increase in the oxidative capacity of the triceps brachii muscle after the crossing. This contrasted with decreased fat oxidation during leg exercise, which occurred parallel to a decreased oxidative capacity in vastus lateralis muscle. Although the number of subjects is limited, these results imply that the adaptation pattern after long-term, prolonged, low-intensity, whole body exercise may vary dramatically among muscles.

Are substrate use during exercise and mitochondrial respiratory capacity decreased in arm and leg muscle in type 2 diabetes?

“…To the best of our knowledge, we are the first to report similar MFO determined during progressive arm exercise in patients with type 2 diabetes, and in obese and lean controls. In a prior study it was demonstrated that fat oxidation during arm-cranking was increased after 42 days of prolonged low-intensity training without changes in V Á O 2max [34]. In this study V Á O 2max was lower during upperbody exercise in patients with type 2 diabetes and obese control individuals compared with lean controls, but this did not lead to a decreased fat oxidation during upper-body exercise in patients with type 2 diabetes and obese controls.…”

XP-Antarctik Expedition: The Effect of a Month-Long Expedition in Antarctica on Physiological Performance

“…This change can favor the improvement of the maximal aerobic tests, as observed in the present study. However, previous studies do not corroborate this improvement in the aerobic capacity (Helge et al, 2003;Stroud, 2001), where the VO 2 max decreases after the expedition. The previous studies used treadmill running progressive tests where VO 2 max was analyzed, but not measured during a progressive specific test.…”

“…A similar finding was observed in previous studies, where ski-trekkers slightly increased their lean mass (Frykman et al, 2003), promoting an increase in physical capacity. However, many other ski-trekkers decreased their lean mass after a similar expedition (Frykman et al, 2003;Halsey & Stroud, 2012;Helge et al, 2003;Paulin, Roberts, Roberts, & Davis, 2015). Furthermore, a previous study explained that a sledge-pulling expedition induced vigorous physical activity, promoting gains in lean mass if the energy deficit is minor (Frykman et al, 2003).…”

Field studies of exercise and food deprivation

“…Prolonged exercise alone does not appear to produce this effect [28]. This reduction in fast-twitch muscle fibers is probably a consequence of a decline in activity in the thyroid axis [29], as has been noted in field studies of prolonged work with inadequate dietary intakes [8,30].…”