Table 3.
Cerebral metabolic variables during cycling
 (%) |
0.21 | 0.21 | 0.10 | 0.21 | 0.21 |
|---|---|---|---|---|---|
| Workload (W) | Rest | 124 ± 21 | 124 ± 21 | 226 ± 38 | 279 ± 75 |
| Workload (% of max) | Rest | 44 ± 8% | 44 ± 8% | 81 ± 13% | 100% |
| O2 a-v diff. (mmol) | 3.5 ± 0.3 | 3.1 ± 0.4* | 2.0 ± 0.3*** | 3.8 ± 0.4 | 4.1 ± 0.4*** |
| Oxygen delivery (μmol (100 g)−1 min−1) | 401 ± 28 | 486 ± 41*** | 386 ± 41 | 465 ± 48*** | 435 ± 26* |
 (%) |
40 ± 4 | 34 ± 4*** | 39 ± 5 | 42 ± 4 | 46 ± 3*** |
 (mmHg) |
39 ± 2 | 43 ± 2** | 25 ± 2*** | 39 ± 3 | 40 ± 3 |
 (μmol 100 g−1 min−1) |
158 ± 11 | 156 ± 15 | 136 ± 15** | 189 ± 20*** | 185 ± 19*** |
| CMRCHO (μmol 100 g−1 min−1) | 26 ± 6 | 26 ± 5 | 32 ± 12 | 38 ± 7** | 51 ± 10*** |
 (mmHg) |
0 ± 0 | 3.6 ± 3 | -10.6 ± 4.4*** | -3.6 ± 5.2 | -8.0 ± 4.5* |
| Glca (mmol l−1) | 5.8 ± 0.3 | 5.5 ± 0.3 | 6.8 ± 0.6*** | 5.1 ± 0.3*** | 5.7 ± 0.4 |
| Laca (mmol l−1) | 1.2 ± 0.3 | 1.7 ± 0.8 | 8.8 ± 1.7*** | 4.9 ± 1.5*** | 10.8 ± 1.7*** |
| Glc av diff. (mmol) | 0.6 ± 0.1 | 0.6 ± 0.1 | 0.5 ± 0.1 | 0.7 ± 0.1 | 0.8 ± 0.1** |
| Lac av diff. (mmol) | -0.1 ± 0.1 | -0.1 ± 0.1 | 0.0 ± 0.2* | 0.2 ± 0.2*** | 0.8 ± 0.2*** |
| OGI | 5.8 ± 0.9 | 5.4 ± 1,2 | 4.7 ± 1.3 * | 5.9 ± 1.6 | 5.4 ± 0.9 |
| OCI | 6.2 ± 0.7 | 6.1 ± 0.6 | 4.8 ± 0.5*** | 4.9 ± 0.5*** | 3.8 ± 0.5*** |
, inspiratory oxygen fraction; a-v diff, arterio-venous differences, 
and CMRCHO, cerebral metabolic rate of oxygen and carbohydrate [glucose +½ lactate], respectively; 
, oxygen extraction fraction; 
, cerebral mean capillary oxygen tension; Δ
, changes in cerebral mitochondrial oxygen tension; OCI, oxygen/glucose index; OGI, oxygen/carbohydrate index; *, ** and ***, different from rest, P < 0.05, P < 0.01 and P < 0.001, respectively. Values are mean ±s.d.