# HAL Training in Spinal Cord Injured Patients: A Narrative Review of 10 Years Experience
## 3 Results
### Clinical Trials
Thus, according to the authors, this study was the first to demonstrate improved gait physiology after HAL training in SCI patients. In addition to the frequently addressed ability to walk in patients with SCI, the ability to maintain a seated position for an extended period of time also plays an important role. To evaluate the effect of HAL training on trunk muscle strength, [PERSON] et al. [18] conducted a study in nine chronic (1-10 years since SCI) patients. The HAL intervention consisted of 20 training sessions of approximately 40 min net HAL training time each. Trunk muscle strength was defined as the ability to maintain a seated posture in four directions (anterior, posterior, left lateral, and right lateral) and measured pre- and post-training [18]. An examiner pushed the participant's torso using a dynamometer until the participant could no longer maintain the seated posture. The patients were part of the collective from [PERSON] et al. [15] where the functional recovery results have already been published. Trunk muscle strengths from baseline to after 20 training sessions improved in all directions, however, statistical significance was only shown in the change of lateral trunk muscle strength. Surprisingly for the authors, the changes in anterior, posterior, and lateral trunk muscle strength showed significant positive correlations with age at baseline, indicating that older adult subjects with chronic SCI experienced greater improvements in trunk muscle strength [18]. This contrasts somewhat with the results of [PERSON] et al. [12] who induced a lower level of improvement in gait function (10 MWT-speed) in older adult patients than in younger patients during the chronic phase of SCI. A study by [PERSON] et al. [19], which is based on the same study population as [PERSON] et al. [15], deals with the influence of HAL training on quality of life (QOL). Since paraplegia affects one's entire life, QOL suffers from it and requires follow-up in the course of rehabilitation. Patients performed the already known 20 sessions HAL protocol and were assessed by short Form\(-\)36 questionnaire Japanese version (SF-36v2), WiscI II, FIM motor score, and the Neuropathatic Pain Symptom Inventory (NPSI) self-questionnaire. As with [PERSON] et al. [15] patients were divided into a low walking ability group and a high walking ability group. Baseline values in SF-36v2 of the participants were lower compared to healthy individuals and were not improved in the course of the training. Likewise, WISCI II, FIM motor score, and NPSI did not show significant differences, irrespective of baseline walking abilities. However, a correlation analysis showed positive correlation between FIM motor score and some subscales of SF-36v2 and a negative correlation between NPSI and the change in subscale Vitality and Mental Health, leading the authors to conclude that in their protocol those with higher functional independence and lower pain at pre intervention were more likely to improve [19]. The authors see an explanation for the generally low improvement in QOL in the unchanged pain score, which in turn can be explained by an already low pain prevalence at baseline. The largest study population in a clinical trial with HAL to date is provided by the study of [PERSON] et al. [20]. This involved 121 patients with acute (\(n=47\)) and chronic (\(n=74\)) SCI. Partial results of this collective have been published previously [9; 10; 11; 12; 13; 16; 17]. The aim was to assess whether HAL training is advantageous for acute and chronic participants and if length of time post injury affects the outcome. Significant improvements in treadmill-related parameters (time, distance) and all functional parameters (10 MWT, 6 MWT, WISCI II, LEMS) were reported for the whole group as well as for the subgroups of acute and chronic patients. However, significant differences between acute and chronic participants' outcomes were found in 6 MWT, LEMS, and WISCI II, showing that chronic participants improved significantly less than acute participants did.