Extremely Short–Duration High‐Intensity Training Substantially Improves the Physical Function and Self‐Reported Health Status of Elderly Adults

To the Editor: Aging is characterized by a gradual reduction in skeletal muscle mass, a loss of physical function, and a reduction in quality of life,1 but traditional exercise can be used to attenuate these age-related declines,2, 3 increasing perceptions of physical capabilities, which in turn increases the adoption of physical activity.4 The UK Chief Medical Officer's physical activity guidelines for elderly adults recommend moderate- to vigorous-intensity physical activity several days per week, but a large proportion of the elderly population does not participate in the recommended amounts, with time being reported as the most common barrier to participation.5 High-intensity training (HIT) has been shown to improve health and performance measures substantially,6, 7 but the potential of using HIT in an elderly population is still to be investigated. It is also unknown whether HIT can be used to improve individuals' perceptions of their health and physical ability. The goal of the current study was to determine whether a HIT protocol consisting of progressive, 6-second sprints performed twice per week for 6 weeks could substantially improve the physical function, cardiovascular health, and self-reported health status of an elderly population. Participants were randomly allocated to a control (n = 6; five female, one male; aged 64 ± 2) or HIT (n = 6; four female, two male; aged 65 ± 4) group before baseline measurements were made. Self-reported health status was measured using the Medical Outcomes Study 36-item Short-Form Survey version 2 questionnaire and the Exercise-Induced Feeling Inventory. Physical function was determined using the get up and go test, the sit to stand test, and the 50-m loaded walk test. Participants performed a 12-minute single-stage walking test to determine maximum oxygen uptake (VO2 max), and blood pressure was determined using an automated blood pressure monitor. The HIT intervention was similar to one used previously.8 Upon arrival, participants were fitted with a heart rate monitor. Each session consisted of 6-second all-out cycling efforts. Male participants sprinted against 7% body weight and female participants against 6.5% body weight. The number of sprints in each session was progressively increased throughout the intervention, ranging from six 6-second sprints to ten 6-second sprints. A minimum of 1 minute of recovery was given between sprints, with subsequent sprints not starting until heart rate was below 120 beats per minute. All preexperimental protocols were then repeated in the same order as at baseline. A paired-sample t-test was used to compare the within-group effects and an unpaired t-test to compare the between-group effects. Psychometric data were analyzed using the Wilcoxon test for within-group differences, and between-group differences were analyzed using the Mann–Whitney test. Table 1 shows the values for all variables for both groups at both time points. After the intervention, systolic blood pressure was 9% lower, VO2 max was 8% greater, and the get up and go was 11% better (all P > .05). There was a nonsignificant difference in sit to stand between groups but a significant reduction (14%) within groups. There was also a nonsignificant between-group difference in 50-m loaded walk but a significant within-group reduction (7%). Positive engagement, revitalization, and comparative health were nonsignificantly increased by 16%, 32%, and 18%, respectively. Physical functioning was significantly increased by 14%. Age-related muscular mitochondrial dysfunction may partly explain the exact mechanism by which HIT improves physical function. Traditional exercise and HIT have been shown to improve skeletal muscle mitochondrial function,8 so it is likely that the improvements seen in physical function were related to improvement in skeletal muscle mitochondrial function. Central cardiovascular adaptations to HIT have been shown after 8 to 16 weeks of training.9, 10 Similar adaptations may explain the reduction in systolic blood pressure observed here, whereas increased VO2 max is likely to be due to central adaptations and improved mitochondrial function, as described above. Traditional aerobic and strength interventions have been found to increase self-rated physical functioning by 2% to 4% after 12 months.4 This study suggests that HIT may be used as a time-efficient intervention to increase perceived control over ability to engage in physical activity and a direct means of improving physical health. These data strongly suggests that performing 2 minutes of exercise per week for 6 weeks may be an effective strategy for counteracting age-related functional decline, reducing cardiovascular disease risk and promoting further engagement in physical activity within the elderly population. The authors would like to thank all of the subjects for their participation in the study. Conflict of Interest: None. Author Contributions: Adamson, Babraj: study design, subject recruitment, data collection, analysis, preparation of letter. Lorimer, Cobley: data collection, preparation of letter. Sponsor's Role: None.