There are currently scientific discussions regarding the utility of stretching exercises which are regularly recommended and conducted as a part of preexercise protocols to reduce injury and increase performance. Earlier reviews of stretching and flexibility have questioned their value in terms of injury prevention, delayed onset of muscle soreness, and improvement of performance [31
]. In fact, what occurs physiologically with stretching remains unknown [32
]. Due to equivocal evidence thus far, the current American College of Sports Medicine's guidelines for exercise testing and prescription [33
] recommended the removal of static stretching as part of a warm-up routine for strength and power activities. Additionally, based on available evidence, the 2011 ACSM position statement for guidance on prescribing exercise suggests performing flexibility after cardiorespiratory endurance or resistance exercise for general fitness programs. This position stand highlighted the need for further research to ascertain the effects of various flexibility prescriptions for various activities and performance goals. From the present review, there is not enough consistent evidence to make recommendations for any specific prescriptions of type, frequency, duration, or length of program related to flexibility training; particularly no specific recommendations can be made regarding the program or dose response of flexibility training to the focus of the present study, the transfer of flexibility gains to functions of daily life, or ability to live independently. A recent systematic review of 106 articles relating the effects of pre-exercise acute-passive static stretching on maximal muscle performance provided 74 methodologically sound studies providing 104 findings [34
]. This paper showed that 50% of the 104 findings reported significant reductions in task performances, and the authors concluded that static muscle stretches totaling less than 45
s can be used in pre-exercise protocols without significant decrement to strength, power or speed type tasks; thus a conclusion was to recommend stretches held for at maximum 45
s to avoid loss of strength. Shrier [35
] had also previously reported the potential negative acute effects of stretching on performance, but additionally reviewed the literature regarding regular stretching on performance which indicates that regular stretching improves force, jump height, and speed performance. Both reviews recommend further synthesis of the literature with respect to the effects of other forms of stretching on various performance measures.
The difficulties of the ability of this paper to provide a consensus on flexibility training prescription for healthy older adults include the lack of well-conducted studies focused on flexibility in older adults and the lack of consistency in the flexibility protocols employed, functional outcomes measured, and functional results observed. As such, according to the criteria used to assess level of evidence, to recommend stretching/flexibility exercises as a routine component of an exercise program for older adults to enhance health or functional abilities is Level 4, Grade C. The more influential studies in this paper (based on focused flexibility protocols with clear functional outcomes and relatively large sample sizes) [11
] showed very comparable effects to the overall outcomes of the 26 studies, namely, an ambivalence in the value of flexibility training on functional outcomes that may be related to maintenance of independence in daily activities of older adults. Of these six studies, 5 were RCTs with an average quality assessment score of 18 out of 24. Only two of the six showed improvement in flexibility and functional outcomes ([14
] 16/24; [16
In the sub-group (≥80 years), frail, and assisted-living populations there were significant improvements seen in functional reach, sit-to-stand, and 30
m walk times, but no changes in the PPT, and mixed results were observed for flexibility, strength, balance, and TUG tests. This sub-group was similarly ambivalent in the role of flexibility training with functional outcomes to the rest of the study populations, although this group had less consistency in the flexibility-related outcome measures. Frequency and duration differences between studies showed no noticeable differences in outcomes. When different muscle groups were targeted, the flexibility outcomes were expectedly fairly body-part specific. Regarding the different flexibility training methods, active-assisted (AA) stretching had positive and sometimes significant improvements in several outcome measures as compared to the inactive control group, but less significant than the improvements seen with the PNF techniques. Weighted flexibility exercises were similar to nonweighted exercises in one study, but significantly better than nonweighted exercises in another. One study showed ACR-PNF to be much more effective than CR-PNF and static stretching for both ROM and EMG activity. The overall results point to PNF stretching being more effective than non-PNF techniques for improving flexibility outcomes, but not necessarily functional outcome measures.
While flexibility training interventions synthesized in the present paper have been shown to increase flexibility and joint ROM, no consistent increases in functional outcomes have been observed. Therefore, future studies should consider the relationship that increased flexibility and joint ROM have with functional outcomes to determine if the increased flexibility is beneficial and worthwhile in terms of maintaining or increasing functional capacity for healthy older adults. More research is also needed regarding the relationships between outcome variables (i.e., how one variable such as functional reach would relate to another variable such as the timed up-and-go) and on the relationships between outcome measures and quality of life through self-reported functioning/quality of life questionnaires to best determine the applicability of the outcome measures.
Older adults are less concerned with high performance benefits from increased flexibility and more focused on being safely active and safely performing activities of daily living [36
]. Injury and fall prevention are also common motives for recommending flexibility programs to older adults. The 2011 ACSM position statement notes that flexibility training may enhance postural stability and balance when combined with resistance training; however, no consistent link has been shown between regular flexibility exercise and a reduction of musculoskeletal injuries or delayed onset of muscle soreness [4
]. However, despite the growing literature describing the relationship of flexibility to injury risk in younger populations [31
], there is little research regarding older adults.