Setor de Fisiologia Clínica do Exercício, Disciplina de Pneumologia, Departamento de Medicina, Universidade Federal de São Paulo, SP, Brasil.
Braz J Med Biol Res. 2011 Apr;44(4):354-60. doi: 10.1590/s0100-879x2011007500023. Epub 2011 Mar 4.
We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ) of oxygen consumption (VO(2)) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the VO(2) on-exercise mean response time (MRT) and the gas exchange threshold (GET). The ΔVO(2)/ΔWR slope was calculated up to GET (S(1)), above GET (S(2)) and over the entire linear portion of the response (S(T)). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak VO(2) and muscle performance were lower in patients than controls (P < 0.05). Patients had significantly lower ΔVO(2)/ΔWR than controls, especially the S(2) component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min(-1)·W(-1), respectively; P < 0.001). There were significant relationships between ΔVO(2)/ΔWR (S(T)) and muscle endurance, MRT-VO(2), GET and peak VO(2) in MM patients (P < 0.05). In fact, all patients with ΔVO(2)/ΔWR below 8 mL·min(-1)·W(-1) had severely reduced peak VO(2) values (<60% predicted). Moreover, patients with higher cardiopulmonary stresses during exercise (e.g., higher Δ ventilation/carbon dioxide output and Δ heart rate/ΔVO(2)) had lower ΔVO(2)/ΔWR (P < 0.05). In conclusion, a readily available, effort-independent index of aerobic dysfunction during dynamic exercise (ΔVO(2)/ΔWR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress.
我们确定了在递增负荷运动中，线粒体肌病（MM）患者 VO₂ 消耗率（Δ）与应用功率输出（工作率=WR）之间的动态关系的反应特征和功能相关性。14 名经活检证实的 MM 患者（7 名男性，年龄 35.4±10.8 岁）和 10 名久坐对照组（6 名男性，年龄 29.0±7.8 岁）进行了递增负荷踏车测试，以确定 VO₂ 运动中平均反应时间（MRT）和气体交换阈值（GET）。计算 ΔVO₂/ΔWR 斜率直至 GET（S1）、高于 GET（S2）以及整个反应线性部分（S T）。通过等速测功计测量膝关节肌肉耐力。正如预期的那样，患者的峰值 VO₂ 和肌肉表现均低于对照组（P<0.05）。与对照组相比，患者的 ΔVO₂/ΔWR 明显较低，尤其是 S2 成分（6.8±1.5 与 10.3±0.6 mL·min⁻¹·W⁻¹，分别；P<0.001）。在 MM 患者中，ΔVO₂/ΔWR（S T）与肌肉耐力、MRT-VO₂、GET 和峰值 VO₂ 之间存在显著关系（P<0.05）。实际上，所有 ΔVO₂/ΔWR 低于 8 mL·min⁻¹·W⁻¹ 的患者的峰值 VO₂ 值均严重降低（<60%预测值）。此外，运动中心肺压力较高的患者（例如，较高的 Δ通气/二氧化碳输出和 Δ心率/ΔVO₂）的 ΔVO₂/ΔWR 较低（P<0.05）。总之，在动态运动中，一种易于获得、与努力无关的有氧功能障碍指标（ΔVO₂/ΔWR）在 MM 患者中通常降低，与功能损害增加和心肺压力增加有关。
