Adeguamento cardiorespiratorio all'esercizio fisico nel paraplegico. Effetto dell'allenamento e del livello di lesione

This paper is aimed A) to extend the data base on the cardiorespiratory adjustments and on the level of physical fitness of spinal cord injury (SCI) subjects living in Italy, a country where participation in social and community activities is still quite difficult to wheelchair dependent individuals, and b) to evaluate the role played by training condition in respect to the role of injury levels in determining the maximal attainable performance capacity. A total of 24 male SCI were selected as follows: elite marathon racers with T1-T4 (n=4; 23-28 yrs; 49-65 kg BW) and T7-L2 (n=4, 22- 30 yrs, 59-67 kg BW) injury levels; T7-L2 moderately trained SCI basketball (n=16; 27±1 (SE) yrs, 70±3.4 kg BW). A group of age-and-gender matched sedentary able body individuals acted as controls. Oxygen consumption (V̇O2), pulmonary ventilation (V̇E) and heart rate (HR) were measured at the last min of 3-5 submaximal exercises of increasing intensities, each lasting 7 min, and at exhaustion (peak values, p), during wheelchair roller ergometer locomotion. Blood lactate concentration [LA] was also detected at the 5(th) min of recovery. During submaximal exercise HR/VO2, relationship increased linearly in all individuals with quite difference slopes: in marathon racers at a V̇O2=1500 ml·min-1 HR was almost maximal in T1-T4, and reached 120-140 b·min-1 in T7-L2. In T7-L2 moderately trained SCI a V̇O2=800 ml·min-1 was accompanied by a HR ranging between 90 and 140 b·min-1 (in controls between 95 and 120 b·min-1). V̇E was considerably different among subjects for a given V̇O2. At exhaustion V̇O2p and V̇Ep per kg and [LA]p were extraordinarily high for the small muscle mass activated. In T1-T4 marathon racers V̇O2 was 31±4 ml·min-1, V̇E 1184±102 ml·min-1 and [LA] 7.2±2 mmol·l-1, and, respectively, 43±2 ml·min-1, 1735±161 ml·min-1 and [LA] 13±1 mmol·l-1 in T7-L2. On the contrary, in the moderately trained basketball SCI and controls, 50% lower values were observed. When V̇O2 p values were evaluated as a function of the injury level in SCI with similar training condition, and the data from the literature were also taken into account, practically no changes occurred from L2 to T6. On the contrary from T6 to C6 a dramatic V̇O2p decrease was observed, reaching at C6 injury level a value about 50% lower. In conclusion, intense aerobic training increases the maximal capacity to perform exercise up to the double of the value of untrained SCI subjects with the same injury level. The level of injury impairs the maximal performance mainly above T6 where certain autonomic reflexes required for normal responses to exercise are disrupted.