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Figure 21.4. Relationship between cardiovascular and neuromuscular adaptations to exercise. Training enhances metabolic and mechanical efficiencies, resulting in increased exercise capacity and reduced energy expenditure, respectively. Fractional utilization is the percentage of peak exercise capacity required to exercise at a fixed submaximal workload. When the numerator (energy expenditure) decreases and the denominator (exercise capacity) increases, fractional utilization is reduced, resulting in greater resistance to fatigue and exercise tolerance.

Figure 21.4. Relationship between cardiovascular and neuromuscular adaptations to exercise. Training enhances metabolic and mechanical efficiencies, resulting in increased exercise capacity and reduced energy expenditure, respectively. Fractional utilization is the percentage of peak exercise capacity required to exercise at a fixed submaximal workload. When the numerator (energy expenditure) decreases and the denominator (exercise capacity) increases, fractional utilization is reduced, resulting in greater resistance to fatigue and exercise tolerance.

cardiovascular adaptations enhance metabolic efficiency, which results in increased exercise capacity. Neuromuscular adaptations (e.g., changes in motor unit recruitment and timing resulting from training and motor learning) improve mechanical efficiency, which lowers the energy costs of physical activity. Improvements in metabolic and neuromuscular efficiencies together contribute to reduced fractional utilization - the percentage of peak exercise capacity required to exercise at a fixed submaximal workload. As a consequence, the cardiac reserves available for other activities are greater, thereby enhancing resistance to fatigue and exercise tolerance.

Changes in energy expenditure with neurorehabilitation

To achieve immediate reductions in the energy cost of hemiparetic gait, Hesse et al. (2001) recommended that patients increase locomotor efficiency by walking at speeds higher than their preferred speeds. Also, use of ankle-foot orthoses has been shown to reduce energy costs of hemiparetic gait from 10% (Dasco et al., 1963; Corcoran and Brengelmann, 1970) to 35% (Franceschini et al., 2003). In contrast, paraplegic gait with support from crutches requires 43% greater energy expenditure than does wheelchair propulsion (Waters and Lunsford, 1985).

Few investigators have studied training-induced changes in the energy cost of neurologic gait. An exercise training program designed to improve ambulatory efficiency of patients with traumatic brain injury failed to reduce energy costs despite a 15% improvement in VO2peak (Jankowski and Sullivan, 1990). In contrast, a pilot study involving subjects with incomplete spinal cord injuries reported a 32% reduction in the energy cost of walking after 12 weeks of body weight-supported treadmill training (Protas et al., 2001). Two early studies on the effects of stroke rehabilitation reported mean reductions in energy expenditure of walking of 30% (Dasco et al., 1963) and 23% (Hash, 1978). In the first clinical trial of aerobic training after stroke, the magnitude of improvements in peak workload (43%) and exercise time (40%) exceeded that of VO2max (13%), intimating that muscular efficiency improved to a greater extent than aerobic capacity (Potempa et al., 1995). In a subsequent training study of patients poststroke, Macko and associates (2001) interpreted gains observed in ambulatory workload capacity as a reflection of both improved exercise capacity and greater gross motor efficiency. The investigators postulated that central neural motor plasticity, mediated by the repetitive, stereotypic training, underlie these adaptations.

21.4 Recommendations for conditioning programs in neurorehabilitation

Specific guidelines for training neurologic populations are lacking. However, the general principles of exercise training outlined by the American College of Sports Medicine (2000) appear to be applicable to aerobic conditioning programs for individuals with upper motor neuron damage. The recommendations outlined in Table 21.3 are derived mainly from the clinical and research experiences of the author.

21.5 Conclusions

Primary and secondary neuromuscular and car-diorespiratory impairments associated with most neurologic conditions adversely affect both exercise capacity and muscular efficiency, giving rise to unfavorable consequences on mobility, energy costs, and quality of life. Despite the pervasive decondi-tioned state in individuals with neurologic patients and the unequivocal benefits of exercise on health status, details regarding effective strategies to improve endurance and efficiency of movement are lacking. Research, albeit limited, suggests that patients with neurologic impairments respond to exercise training in essentially the same manner as individuals without impairments. These findings have been a catalyst for the introduction of more aggressive, multisystem approaches to neurorehabilitation designed to interrupt the cycle of debilitation and enhance neurologic recovery.

Table 21.3. Recommendations for exercise training of individuals with neurologic impairments.

Screening. Thorough review of the health record of potential participants is critical to identify cardiorespiratory and musculoskeletal problems that may limit participation in a training program. Cardiac screening, including an exercise stress test with continuous ECG and periodic blood pressure monitoring, is essential for those with cardiac co-morbidities. Preparation of participants: Participants should be advised to avoid eating 2 h before training and to empty bowel and bladder prior to training. Comfortable clothing and supportive footwear, conducive to dynamic exercise, prepare the participant both physically and psychologically for training.

Program design

• Setting. When training high-risk individuals, such as patients in the early phases of neurologic recovery or with significant cardiac co-morbidities, an adverse event protocol and emergency medical equipment and trained personnel during training sessions must be available. For lower-risk individuals, supervised community (Eng et al., 2003) or home-based (Duncan et al., 2003) aerobic exercise programs may be a safe option. Since thermal dysregulation is common in patients with neurologic impairment - particularly multiple sclerosis (Ponichtera-Mulcare, 1993) and spinal cord injuries (Price and Campbell, 1999) - careful control of ambient temperature and provision of fans, spray bottles, towels, and a water cooler are recommended. A water bottle with volumetric indicators is useful to monitor hydration prior to exercise and rehydration following exercise. The training environment should be wheelchair accessible, with adequate space to permit transfer to/from exercise equipment.

• Scheduling. Many patients with neurologic involvement report a decline in energy level in the afternoon. If fatigue is a concern, training should be scheduled for morning hours, when circadian body temperature is at its lowest. For certain patient groups, including people with Parkinson disease, timing of medication use to optimize performance during training is an important consideration.

• Frequency. Although fitness can improve with twice-weekly sessions, optimal training requires 3-5 sessions per week (American College of Sports Medicine, 2000). Very deconditioned individuals may benefit from multiple brief daily exercise sessions.

• Duration: A minimum of 20 min of exercise within the target zone for training per session is required to elicit a training effect (American College of Sports Medicine, 2000). For those with low fitness levels, training may be initiated with 5-min exercise "bouts" with rest periods between bouts. Two additional 5-min periods are required for warm-up and cool-down; hence, the minimal time required to complete a training session is 30 min.

• Mode of training. Training modes include treadmill walking with or without body weight support, bicycle ergometer with toe clips and heel-straps, arm-leg ergometer, wheelchair ergometer, stepping machine. Although arm ergometry activates a small portion of total muscle mass, its effectiveness in the aerobic training of patients with quadriplegia has been demonstrated (DiCarlo, 1988). Muscle strengthening exercises should also be prescribed since the combination of physical conditioning and muscle strengthening (e.g., abdominals, hip and knee flexors and extensors, hip abductors, ankle dorsiflexors and plantarflexors) improves outcome (Teixeira-Salmela et al., 1999).

• Intensity. Initial exercise intensity and progression must be individualized. Deconditioned individuals can benefit from intensities as low as 55-64% of maximal HR (American College of Sports Medicine, 2000). Continuous HR monitoring and periodic blood pressure readings are recommended. Rating of perceived exertion can serve as a valid proxy to more physiologic measures (Borg, 1982). Evidence suggests that music, properly timed to rhythmic motor events such as walking or cycling, potentiates muscle activation and may be beneficial in pacing movement (Rossignol and Jones, 1976, Mcintosh et al., 1997).

• Adherence to program. Benefits of training are reversible unless some form of training stimulus is maintained. Strategies to enhance long-term exercise adherence include gradually progressing the exercise intensity, establishing regularity of training sessions, minimizing the risk of muscular soreness, exercising in groups, emphasizing enjoyment in the program, providing on-going positive reinforcement, and using activity logs and charts to record participation and progress. Training sessions should be scheduled at a convenient time and in an accessible location, and if feasible, assistance with transportation and childcare should be offered.

Outcome measures. Walking speed over 10 m and the 6-min walk are clinical measures used to determine functional capacity and are reliable, valid, and easily executed. Blood pressure and HR should be recorded at initiation and termination of the 6-min walk (Eng et al., 2002).

Lifestyle modifications. To sustain improvements in fitness level, education and counseling regarding the daily physical activity, nutrition, energy conservation techniques, and coping strategies are essential.

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Run for Your Life The Health Benefits Of Treadmills

Run for Your Life The Health Benefits Of Treadmills

Improve your hearts health? Lose a few pounds? Or simply become more active? If that is your goal, then maybe its time for you to do some exercise. But where do you start?

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