Sit to stand test (STS)

The use of other sub maximal physical performance tests such as the sit to stand test (STS) has been suggested as an appropriate indicator of physical fitness in older adults (Schaubert & Bohannon, 2005). It is commonly used with older adults to determine a person’s level of transfer function and the test has been shown to be

an indicator of lower extremity strength (Bohannon, 2002; Janssen et al., 2002c;

Ritchie et al., 2005; Nordin et al., 2008). As it is a measure of lower limb strength it provides added value to measurements obtained from HGD. It is a reliable and valid measure in an ageing population and has been generally accepted as an indicator of functional status in older adults (Ritchie et al., 2005). Indeed it has been demonstrated to be a useful tool in both research and within the practice setting as it is considered a measure of not only functional ability but also an indicator or proxy of lower limb strength, balance and mobility (Lord et al., 2002). The motion of standing from a seated position is a key component of many daily activities e.g.

rising from a chair and walking, getting out of a car or bath etc. and as such is a particularly useful measure in older adults (Janssen et al.. 2002c). Indeed as the number of sit to stand motions performed each day by an older adult may be as many as 50 (Bohannon et al., 2008) it is seen as a critical determinant of a person’s ability to live independently and it is a particularly important skill to maintain in ageing populations. An inability to perform the sit to stand motion leads to impaired function, mobility and impairment in ADL and in extreme cases even death (Guralnik et al., 1995). The STS clearly provides important information about a person’s functional ability and it has the advantage of being a quick and inexpensive measure which does not require either a skilled practitioner or any specific training (Sterky &

Stegmayr, 2005). Due to the positioning of the person undertaking the test, the test itself includes components of both upper and lower limb function and the test is considered to have both convergent construct (the extent to which the same trait is measured by different methods (Carmines & Zeller (1979)) and discriminate validity (the extent to which traits are distinct (Carmines & Zeller 1979)) as a result of its association with knee extension force and leg press force (Whitney et al., 2005).

The use of STS in an older population has the potential to highlight those people who may have a greater need for assistance as lower STS scores have been reported in older individuals who report a greater need for assistance with ADL (Bohannon, 2002; Ritchie et al., 2005). It is therefore a key measurement although there are a number of different STS tests available for use. All the tests are based on the quantification of the number of repetitions completed in either a given period of time or the time taken to perform a set number of repetitions (Bohannon, 2002).

The variations in the tests include the sit to stand 5 (STS5), where the time to complete 5 repetitions is recorded, the sit to stand 10 (STS10), where the time to complete 10 repetitions is recorded, and the sit to stand 60 (STS60) where the number of repetitions completed in 60 seconds is recorded. Each test has a slightly different purpose with the STS5 and STS10 being considered in part indicators of muscle strength, and the STS60 an indicator of muscle endurance and fatigability (Bohannon, 2002).

The STS5 test has been shown to accurately reflect lower limb strength (Lord et al., 2002) and is therefore widely used particularly among older adults due to its shorter duration and thus enabling the majority of older adults to complete the test (Ganacher et al., 2012). As a one off measurement STS5 can be applied easily in many settings and provides an objective measure of lower limb muscle strength which is also a reflection of lower limb function and overall functional ability (Guralnik et al., 1994).

The time taken to perform the test can then be compared with normative values for the population. As there have been a number of studies which have used the STS5 in older adults Bohannon (2006) has reviewed the data and produced a meta-analysis of normative values for people aged 60 years and over. Data has been

categorised by age group but not by gender as there was no apparent differences in performance between men and women. Normative values are shown in table 1.4 with the upper 95% CI being used as the cut-off time for worse than average performance (Bohannon, 2006).

Table 1.4 Meta-analysis of sit to stand performance times in older adults (adapted from Bohannon, 2006)

sit to stand time (s)

age (years) n mean time (s) 95% CI

60 - 99 20617 12.1 12.1,12.1

60 - 69 4184 11.4 11.4,11.4

70 - 79 8450 12.6 12.6,12.6

80 - 89 344 12.7 10.7,14.8

STS5 will be used within this study and unless otherwise stated STS will refer to the STS5 test. This test is clearly simple to perform and provides detail of lower limb function but due to its short duration does not reflect endurance. Endurance is also important in terms of functional ability as whilst it is important that a person can rise from a chair to enable them to function around their own homes a level of endurance will enable them to engage in additional activities and may enable them to leave their home and walk to the shops etc. Additional measures to complement the STS and HGD can therefore provide greater depth of information about a person’s functional ability.