In summary, our data showed that both the warm exposure and the diurnal increase in body temperature influence muscle contractility and consequently muscle strength. However, the improvement in muscle contractility after these two passive warm-ups cannot be combined in order to improve force to a greater level.

No abstract

Functional imaging studies in normal humans have shown that the supplementary motor area (SMA) and the primary motor cortex (PMC) are coactivated during various breathing tasks. It is not known whether a direct pathway from the SMA to the diaphragm exists, and if so what properties it has. Using transcranial magnetic stimulation (TMS) a site at the vertex, representing the diaphragm primary motor cortex, has been identified. TMS mapping revealed a second area 3 cm anterior to the vertex overlying the SMA, which had a rapidly conducting pathway to the diaphragm (mean latency 16.7 ± 2.4 ms). In comparison to the vertex, the anterior position was characterized by a higher diaphragm motor threshold, a greater proportional increase in motor-evoked potential (MEP) amplitude with voluntary facilitation and a shorter silent period. Stimulus-response curves did not differ significantly between the vertex and anterior positions. Using paired TMS, we also compared intracortical inhibition/facilitation (ICI/ICF) curves. In comparison to the vertex, the MEP elicited from the anterior position was not inhibited at short interstimulus intervals (1-5 ms) and was more facilitated at long interstimulus intervals (9-20 ms). The patterns of response were identical for the costal and crural diaphragms. We conclude that the two coil positions represent discrete areas that are likely to be the PMC and SMA, with the latter wielding a more excitatory effect on the diaphragm.

A reliable submaximal test for assessing cardiorespiratory function would be of interest in clinical practice. Baba et al. (1996) proposed the oxygen uptake efficiency slope (OUES) derived from the relation between oxygen uptake (VO2 [ml x min (-1) x kg (-1)]) and minute ventilation (VE [L x min (-1)]) during incremental exercise. We evaluated the validity of OUES by comparing maximal oxygen uptake (VO2MAX) predicted from OUES to measured VO2MAX in 50 healthy males who performed a maximal treadmill test. They had widely differing physical fitness levels (VO2MAX range, 32.7 to 80.2 mlO2 x min(-1) x kg(-1). Predicted VO2MAX was not significantly different (p > 0.99) from measured VO2MAX (56.8 7.0 vs. 56.8 8.8 mlO2 x min 1 kg(-1). The limits of agreement (Bland Altman, 1986) were plus or minus 10.5 mlO2 x min(-1) x kg(-1). Although OUES and VO2MAX were significantly correlated (r = 0.79), the wide interindividual variations in the difference between these two parameters may limit the usefulness of OUES in clinical practice.