Design Recommendations for Nordic Pole & Cane Combination Hannah Nolte DfHV Individual Project October 28, 2019 Introduction: The percentage of older adults in the current population of the United States is increasing at an unprecedented rate and this increase has led to an intensified focus on “successful ageing” techniques [1]. There are many components to “successful ageing” and the design being proposed here will assist with the goal of high physical function (one of the three main components of the original successful ageing theory) [2,3]. Ageing contributes to a wide array of physical, cognitive, and perceptual changes throughout the lifespan, many of which become noticeable during middle or late stage adulthood [4]. The rate of physical function decline due to ageing can be reduced by exercise intervention [5,6]. Exercise intervention can also reduce the prominence and severity of ageing effects [5]. A commonly recommended exercise intervention is walking because it has been shown to improve physical and cognitive function [6–8]. It is recommended that healthy older adults get 7,000-10,000 steps a day [9]. A more full-body workout, , is growing in popularity in the United States [10] and has many health benefits for older adults [11,12]. Nordic walking involves using two sticks or poles that are similar to ski poles (ski poles are longer in length) while walking. Walkers apply force to the ground through the poles. Greater improvement in shoulder, arm, and trunk strength can be seen from Nordic walking compared to free walking (i.e., regular walking) [11]. Health benefits in older adults observed while participating in regular Nordic walking include improved indicators of aerobic fitness, more lumbar flexibility (compared to inactive older adults), lower mass, and smaller hip to waist ratio [12]. This proposal suggests a product design that combines Nordic walking poles with a cane because both can serve as mobility aids for older adults. Almost a quarter of older adults (65+ years) reported the use of a mobility aid (e.g. canes, walkers, wheelchairs) within the last month when surveyed [13]. Walking with Nordic walking poles has many health benefits [12], but canes are the preferred walking aid of older adults [14]. A cane and Nordic walking pole combination would allow older adults the flexibility of using a cane when they prefer but the chance to use walking poles when it is convenient, without having to replace one device for the other. Thus, allowing them the opportunity to moderate the effects of ageing and stay healthy through Nordic walking while having the cane option when the cane is more ideal for the situation. Existing Products: Nordic walking sticks come in two broad categories, one-piece or adjustable. One-piece Nordic walking poles come in varying lengths. They are usually stronger and lighter, but each person must be custom fit with the correct walking pole length. Decathlon sells their NW Nordic Walking Poles P100 ($24.99) in six sizes including 102.62cm, 106.68cm, 109.22cm, 114.30cm, 124.46cm, and 127.00cm (Fig. 1) [15]. Ski Walking: American Nordic Walking System sells their SWIX Carbon Nordic Walking poles (Fig. 2) by stature with their options ranging 4’0”- 6’10” (121.92cm-208.28cm) but their poles are much more expensive ($149.99) [16]. Another company, LEKI, sells their Flash Carbon poles ($119.95) in lengths 100cm-130cm at 5cm intervals (e.g. 100, 105, 110… 130) (Fig. 3) [17].

Figure 2. Ski Walking: American Nordic Walking Figure 1. Decathlon NW System SWIX Carbon Nordic Figure 3. LEKI Flash Nordic Walking Poles Walking Poles [16]. Carbon Nordic walking P100 [15]. poles [17].

Adjustable Nordic walking poles are commonly one-size-fits-all and they usually collapse for easy travel. Some are telescoping in design while others have a twist and lock mechanism, usually 2-3 segments. Montem, who claims to sell the #1 rated Nordic walking poles, sells three types of adjustable walking poles (Fig. 4) [18]. The Pro Nordic Fitness pole ($69.99) has two twist and lock segments and the adjustability ranges from 81cm-137cm [18]. The 3K Carbon Fiber Trekking Pole ($119.99) has three telescoping segments and the adjustability ranges from 61cm-135cm [18]. Montem’s Ultra Z Folding Trekking Poles ($79.99) folds/collapses into three segments and the range of accommodation is only 113cm-135cm. Leader Accessories sells their trekking poles ($29.99) with three telescoping segments and an adjustability range of 66.04cm-34.62cm (Fig. 5) [19]. The Alpenstock trekking poles ($24.99) have three telescoping segments and an adjustability range of 63.5cm-135.89cm (Fig. 6) [20].

Figure 4: Montem adjustable Nordic walking poles [18].

Figure 6: Alpenstock trekking Figure 5: Leader Accessories poles [20]. Trekking Poles [19].

There are many more options for canes (e.g., more sizes, types, grips) compared to Nordic walking poles. Custom canes can be bought easily on the internet but there are also more standard, mass-produced cane options, as well. The Sky Med Stand Alone Cane ($27.00) and has adjustability of 76.2cm-99.06cm (Fig. 7) [21]. The Days Steel Bariatric Offset Handle Adjustable Cane comes in two sizes, standard ($89.99) and tall ($52.99), with adjustability ranges 72.39cm-95.25cm (2.54 cm increments) and 95.89cm– 118.75cm (Fig. 8) [22]. The AliMed Stable Base Quad Cane ($29.00) and has an adjustability of 73.66cm-96.52cm (2.54 cm increments) (Fig. 9) [23].

Figure 8. Days Steel Bariatric Offset Figure 7. Sky Med Stand Alone Handle Adjustable Cane [22]. Cane [21].

Figure 9. AliMed Stable Base Quad Cane [23].

The existing product most similar to the product this design proposes is the Trolax Nordic walking stick and cane combination ($35.99) [24]. The Trolax combination (Fig. 10) has an adjustability of 51cm– 110cm by utilizing a four segment telescoping design [24]. It has both a cane and a walking stick grip, but the product does not have the ability to become two walking sticks, it can only extend into one walking stick.

Figure 10. Trolax Nordic walking stick and can combo [24].

Target Population: The target population for this design proposal is persons of 60+ years of age in the United States (58.8% female and 41.2% male according to the 2010 census for 65+ years of age [25,26]). 60 years of age was selected as the minimum age because that is when functioning motor units in the muscles start to deteriorate at a noticeable rate causing muscle wasting and weakness (a key point in which Nordic walking could be beneficial) [27]. No maximum age was chosen because all adults age at different rates and maintain different levels of physical activity. Realistically there may be an age at which free walking is better suited for older adults than Nordic walking, but it is unlikely to be consistent for all individuals. Also, all healthy adults 20+ years of age are recommended to get at least 7,000 steps a day and this recommendation is only reduced due to illness, not according to age [9]. Since physical activity recommendations are consistent for all adults, this design did not want to limit the use of this product by limiting the age. In addition, the gender ratio of the entire US 65+ years age group will be used because both genders can benefit from Nordic walking, thus the product should work well for as much of the population as possible. There was no information found regarding whether US men or women are more likely to participate in Nordic walking. The product will be designed with older adults generally in mind. This design will be based on a model created using the ANSUR II data and applied to the NHANES data of the appropriate ages. The NHANES data does have a maximum age of 80 years. NHANES data is still reasonable to use because it is the most representative set of data for adults in the US and Nordic walking would logically become less suitable for many individuals older than 80 years of age due to the effects of ageing (muscle weakness, decreased bone density, loss of flexibility- see primer for more details on the effects of ageing). Using ANSUR II to create a model is reasonable because the greatest anthropological measurement difference for older adults is stature [28], which will be used as a predictor in the model. Relevant Anthropometry: There are a few suggested ways to make sure that a person’s Nordic walking poles are the correct length. Nordic Walking suggests two methods for adjusting the lengths of adjustable Nordic walking poles, either eye-ball or measure [29]. Eye-balling involves adjusting the pole heights until they touch the ground when you hold them comfortably with your elbows at 90 degrees [29]. Measuring includes adjusting the pole until it is 0.68 times your height [29]. Total Nordic Walking [30] and Nordic Academy [31] both suggest multiplying stature by 0.68 and rounding down to the nearest size. This design will use 0.68 times the stature as the correct length of a Nordic walking pole as seen in the following equation, 푃ₗ = 퐻 ∗ 0.68 eq. 1 where 푃ₗ is the pole length and H is stature. The length of the pole can also be adjusted by up to ±10 cm when going up/down hill or to change the intensity of the activity [17]. The design will include a margin for this [29]. The Canadian Family Physician recommends that the cane should be roughly the height of the greater trochanter/wrist crease when the patient is standing with their arms at their side (measured from the ground) or the cane should be long enough to reach the ground when the elbow is at a 20-30 degree flexion [32]. This design will use the height of the trochanter to estimate the correct length of the cane. Analysis Summary: A subset of the 2013-2016 NHANES data was used, which only included individuals equal to or above the age of 60 years. Then the weights for the individuals in the older adults subset were modified to give a gender ratio of 58.8% female and 41.2% male (according to the 2010 US census for persons of +65 years of age [26]). Statures from the older adult subset were used in eq.1 to find the distribution of pole lengths needed by the older adult US population. The dimensions of existing Nordic walking poles in the market were then compared to this distribution to assess their accommodation (graphically and quantitatively using percentiles). Then a linear model for male and female (individually) trochanter height was created using the ANSUR II data set. Stature was the only predictor of the model because BMI was not highly correlated with trochanter height and no other length measurements were available in the NHANES data. Residual variance was incorporated into the regression to get a more accurate estimate of older US adults trochanter heights (Fig.11) using the following equation, 푇 = 퐻 ∗ 푎ₗ + 푐 + 푁(0, 푆2) eq. 2 where T is the trochanter height, H is the stature (predictor), 푎ₗ is a coefficient, c is a constant and the last term is the residual variance incorporated randomly N number of times from a normal distribution with a mean of 0.

Figure 11. Older US adult trochanter heights. A linear model for both male and female trochanter heights was based off data from male and female data from ANSUR II. Stature was used as a predictor in the regressions to estimate the trochanter heights of older US adults. Residual variance incorporated.

Bench Marking for Existing Products: One-piece Nordic walking poles did a fairly good job covering the distribution of pole lengths required for a US population of 60+ years (Fig. 12). The six sizes for the Decathlon poles occur at the 7, 24, 36, 62, 96, and 99 percentiles. This spans most of the distribution, only disaccommodating people below the 7 percentile and some less than ideal fitting around a pole length of ~120cm. Ski walking covers the entire distribution, but they have to offer 32 separate pole lengths. LEKI also covers most of the distribution. People below the 3 percentile may be disaccommodated or have to use a pole that has less than ideal fit. LEKI also assumes that 5 cm is a reasonable margin of error on the fit. This is likely to be true for beginners but not for experienced Nordic walkers. One-piece poles being lighter on average would also make them more ideal for older adults.

Figure 12: Benchmarks for one-piece Nordic walking poles. Sizes are shown for Decathlon and LEKI by vertical lines. Ski walking offers 32 sizes (at intervals of a 2.54 cm) so only the minimum and maximum length are shown here by vertical lines.

Adjustable Nordic poles, on average, did a much better job accommodating the lower tails of the distribution (Fig. 13). Adjustable poles covered the tails of the distribution better because they are normally designed for easy, compact travel. Compact travel requires that the pole be able to collapse far shorter than would be required to cover the 0 percentile of required pole lengths for older US adults. The Montem Ultra Z did not accommodate the lower half of the distribution, it only accommodate the 56-100 percentiles. This is most likely due to the foldable design rather than a telescoping or twist and lock design for adjustability. The Montem Pro and 3K, Leader Accessories, and Alpenstock poles covered the entirety of the distribution. The Trolax walking pole and cane combination only accommodated up to the 40 percentile. This is mostly likely due to its primary focus as a cane rather than a walking stick.

Figure 13. Benchmarks for adjustable Nordic walking poles. Minimum and maximum lengths are shown here for each of the adjustable Nordic poles by vertical lines.

Canes did not cover the distribution of US persons that are 65+ years of age as well (Fig. 14). The Trolax walking stick cane combination did the best. This is presumably due to it having to extend past the distribution to function as a walking stick and the requirement that it must collapse shorter than the distribution for compact travel (similar to the adjustable walking poles). The Days cane also did well. It spanned the distribution due to its two sizes which covered the 2-95 percentiles and 95-100 percentiles. Both the Sky Med and the AliMed canes had lower accommodation, 7-99 percentiles and 2-96 percentiles respectively.

Figure 14. Benchmarks for adjustable canes. The minimum and maximum lengths are shown for each of the adjustable canes by vertical lines. The Days cane comes in two sizes represented by vertical lines of two different colors.

Recommendation: It is recommended that this Nordic walking pole and cane combination design come in two sizes, short and long. Having two sizes for the cane will allow for the required adjustability without making the product overly heavy for older adults. Previous Nordic walking poles and cane designs have accommodated the entire distribution of older adults in the US and this design will do the same to match the accommodation of the market. The short combination will accommodate the 0-50 percentiles of the cane length distribution (trochanter height) and the 0-50 percentiles of the pole length distribution (eq.1). The long combination will accommodate the 51-100 percentiles of the cane length distribution (trochanter height) and the 51-100 percentiles of the pole length distribution (eq.1). Relevant percentiles can be seen in Table 1. Users who are at the very extremes of the distribution (people not represented by the distribution) may not be accommodated by this design. A less than ideal fit for this product will also occur for users who have one measure in the lower distribution and one measure in the higher distribution or vice versa. Percentiles Cane Cane Cane Cane Pole Pole Pole Pole 0 50 51 100 0 50 51 100 (cm) 64.95 84.83 84.98 105.48 88.20 111.93 112.06 132.87

Table 1. Relevant design percentiles. A margin of ±10cm with be added to the design to allow for the user to adjust to their preference and workout intensity [17]. Also, an additional 0.5cm will be added to the length to allow for shoes (a recommended guideline for shoes). A telescoping design of three segments is recommended because it is a common, simple to use, and popular design on the market. It will also easily allow for the necessary adjustability. It is however, recommended that the lever used to lock the segments be modified for easier use by older adults in comparison to existing product levers. These modifications could include making the lever larger (reduce constraints from decreased dexterity in the fingers) and making the lever easier to lock/unlock while still locking safely (reduce constraints due to muscle weakness). It is recommended that the short size product have a minimum length of 55.5 cm, a maximum length of 122.5 cm, and adjustability range of 67 cm. The long size product should have a minimum length of 75.5 cm, a maximum length of 143.5 cm, and a range of 68 cm. Approximately 13.75% of the people in the distribution (Fig. 15) had a mismatch for the two (pole/cane) measures (e.g. one above 50 percentile and one below or vice versa). These people would have a less than ideal fit with the product.

Figure 15. Distribution of design relevant anthropometry. People in the lower left quadrant will be accommodated by the short size and people in the upper right will be accommodated by the long size. People in the top left and lower right quadrants will have a less than ideal fit for either size of the product. Unlike the Trolax combination, this design proposes a cane and Nordic walking combination that can separate into two Nordic walking poles. The health benefits found from Nordic walking were observed when participants were using two poles [12] and using two poles while walking guarantees that increases in shoulder, arm, and trunk strength are seen on both the right and the left side of the body [11]. To form the cane, it is recommended the two poles snap together near the cane handle (near the top of the product) and at the bottom. The poles have to be easily separated by older adults but still secure enough to not come apart when the product is being used as a cane. This design also recommends two types of grips, one for the walking pole function and one for the cane function. The cane grip should be on only one of the poles and should be similar in size to grips seen on canes in the market. Only one pole should have the cane grip to prevent the grip from becoming too wide to use when the poles are snapped together. No cane product descriptions reported grip size for comparison so measurements for grip are not presented here (Cascade Healthcare Solutions sells grip replacements for canes of size 4.5 x 1.25 inches [33]). The cane grip should not be included in the total length measurement recommended above. Each pole should also have grips near the top of the pole for use during the walking function. They should be similar in size to the grips seen for other Nordic walking poles on the market (again, no product descriptions reported grip size for a comparison so measurements for grip are not presented here). The grips for walking should be included in the total length measurement presented above. Grips and segment locks should be distinctly different colors than the rest of product but color combinations of white/yellow, blue/green, dark blue/black, and dark red/purple should be avoided because they are difficult for older adults to distinguish [34]. The end of the pole should have a simple rubber covering for walking easily on any terrain. The covering should be similar to the end of a simple cane because simple canes are the preferred cane design among older US adults [14]. The product should also have a wrist strap for each pole (can wear both on one wrist when using the cane function), this will prevent the adult from having to bend over and retrieve the product if it slips. It is also recommended that this product come with detail fitting instructions or be fitted to the costumer because it is common for older adults to use a cane which does not fit them correctly [35]. Stickers of distinguishable color should be provided to mark the correct cane and walking pole heights on the device for easy transition for one function to the other. Accommodation Improvement: Design recommendations were given for an older adult population (60+ years of age) in mind rather than just an adult population in general. The needs of older adults can vary from those of younger adults due the effects of ageing. In this way, this design does not accommodate people who were not accommodated before, but improves accommodation for a particular population of people, older adults. The accommodation improvement will be assessed in comparison to the Trolax cane and walking pole combination because it is the most similar product on the market to what this design proposes. Firstly, this design is improved because it has the ability to separate into two walking poles, whereas the Trolax can only extend into one walking pole. The Trolax did accommodate the entire cane length distribution but it only accommodated up to the 40 percentile of the pole length distribution. The walking pole and cane combination presented here covers the entirety of the cane and pole length distributions with two sizes, which greatly increases accommodation for the measure of required pole length. The Trolax has an adjustability range of 59 cm which is slightly shorter than the adjustability ranges of the proposed design, 67cm and 68cm. The adjustability ranges of the proposed design are not unreasonable because the Montem 3K trekking poles have an adjustability range of 74cm. For the presented design, about 13.75% of older adults will not ideally fit into either of the proposed sizes (see above) but they should still be able to use the product (it is recommended that these individuals choose a size depending on the function they will use the most). Design recommendations also include a ±10 cm margin for preference adjustability, meaning that the two sizes have 10 cm of overlap near the 50 percentile. This should help users of less than ideal fit still be able to use the product, they will just have less adjustability for preference. This margin of less than ideal fit improves upon the disaccommodation of 60% of older adults pole lengths which occurs with the Trolax combination. Limitations: The biggest limitation of this design is that there were no individuals over the age of 80 in the data set used to estimate design requirements. It would be logical for persons over the age of 80 to use this design but without data on this age group it is unknown whether this design would accommodate them well. Another limitation is the lack of experimental data. It is recommended that ±10 cm is enough for preference adjustability but that is untested. It is also undetermined if individuals with one measure above the 50 percentile and one below (or vice versa) will truly be able to use the product. It may be that a less than ideal fit makes use of the product uncomfortable. This discomfort may cause this group of consumers not to use the device and they would therefore be disaccommodated. This design also focused on the length of the product and its adjustability range. A more complex, multivariate analysis that considers the grip size, usability, and other pertinent measures should be conducted in the future to achieve a more comprehensive assessment of the products accommodation. Summary: A design was proposed for a cane and walking pole combination for US people that are 60+ years of age. It was recommended that two sizes be sold using a 3 segment telescoping design. The short size product should have a minimum length of 55.5 cm, a maximum length of 122.5 cm, and adjustability range of 67 cm and the long size product should have a minimum length of 75.5 cm, a maximum length of 143.5 cm, and a range of 68 cm. Other design considerations relevant to the population were suggested in the recommendation section. This device was primarily compared to the Trolax walking pole and cane combination, but other canes and Nordic walking poles were also benchmarked for comparison. References [1] Kanasi, E., Ayilavarapu, S., and Jones, J., 2016, “The Aging Population: Demographics and the Biology of Aging,” Periodontol. 2000, 72(1), pp. 13–18. [2] Rowe, J. W., and Kahn, R. L., 2015, “Successful Aging 2.0: Conceptual Expansions for the 21st Century,” Journals Gerontol. - Ser. B Psychol. Sci. Soc. Sci., 70(4), pp. 593–596. [3] Rowe, J. W., and Kahn, R. L., 1997, “The Forum Successful Aging,” Gerontologist, 37(4), pp. 433–440. 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