Physical Activity in Adults With Amputation

Up to 48% of adults following a lower-limb amputation will die within the upcoming year. Lack
of physical activity (exercise) contributes to high death rates. It is recommended that
younger (and middle-aged) adults without a health condition walk 10,000 steps/day to reduce
the risk of chronic health conditions, while recommendations are 7,100 steps per day for
older adults and those with chronic health conditions. Adults with a lower-limb amputation
walking about 21-43% of the recommended 7,100 steps/day. Step activity monitors, such as the
StepWatch (a research-grade accelerometer) and the FitBit (a commercially-available monitor)
provide a means of evaluating physical activity, which is important since patients tend to
over-estimate their level of physical activity. Activity monitor use, however, may not be
possible in every healthcare practice setting, as monitors may cost $100-$600 and someone
must remove the data from the monitor, interpret the data, and enter the data into the
patient's medical record. Therefore, physical activity questionnaires, where the patient
self-reports their physical activity, are ideal in a clinical setting. Unfortunately, to
date, there has been little research looking at the accuracy of physical activity
questionnaires in patients with lower-limb amputations and how these questionnaires measure
up to data obtained from step activity monitors.

In addition to 7,100 steps/day, adults with mobility-limiting, chronic conditions (including
individuals with lower-limb amputations) should participate in ≥150 minutes of
moderate-intensity physical activity per week, with activity in ≥10 minutes per bout.
Moderate-intensity activity has been defined as 3 metabolic equivalents (METs). One MET is
equal to the amount of oxygen one consumes at rest, so 3 METs means that one is consuming 3
times the amount of oxygen one would consume at rest. In healthy adults without a medical
condition this equates to walking 2.6-2.7 mph or 100 steps/minute, while for adults with an
amputation of the leg below-the-knee (i.e. a transtibial amputation), 1.47 mph or 86
steps/minute has been reported to equal 3 METs. Maximal walking speeds for adults with
lower-limb amputations, specifically those who have lost their limb due to poor blood
circulation may be ≤1.67 mph, so one must question if walking 1.47 mph for an extended time
is possible for these patients. Investigators believe that 1.47mph is greater than 3 METs for
adults with a lower-limb amputation who have other medical issues, such as diabetes and
peripheral vascular disease, and who are deconditioned and not participating in physical
activity.

It is important to know what speed (mph) and cadence (steps/minute) equals 3 METs in adults
with a lower-limb amputation with other medical conditions who are currently inactive.
Investigators believe that these patients represent the vast majority of patients that
healthcare providers encounter and must council regarding increasing physical activity
levels. Providers need to know what speed and cadence is equal to 3 METs for inactive
patients with limb loss with other medical conditions, so that providers can appropriately
advise their patients and prescribe exercise.

Walking exercise may occur over-ground or on a treadmill. When an individual with a
lower-limb amputation is walking over-ground, their right-to-left side walking pattern will
be more asymmetrical (uneven) when compared to when they are walking on a treadmill. When
walking is more symmetrical side-to-side (even), the patient may have to expend more energy.
Energy expenditure can be assessed as the amount of oxygen consumed, which can be obtained
while wearing a mask that evaluates the participant's breathing while walking. Among adults
with a lower-limb amputation, energy expenditure studies have generally used treadmills to
look at energy expenditure. Over-ground versus treadmill conditions, however, are different,
and as such, what equals 3 METs (speed, cadence) in each walking condition may vary.

Further, no studies have compared the energy cost of walking in adults who are inactive with
a lower-limb amputation to age-, sex-, and body mass index (computed from height and weight)
-matched adults without an amputation. While studies have evaluated the impact of aging and
limb length of the amputated limb on energy expenditure, few have evaluated modifiable
factors that may impact energy expenditure among adults with lower-limb amputation.
Similarly, little research has explored modifiable factors that may impact physical activity
levels.

The project's goal is to provide knowledge that will improve physical activity prescription
for inactive adults with a single, below-the-knee amputation (i.e. transtibial amputation).

Successful completion of the project may provide healthcare providers with (1) a physical
activity self-report measure that can be used in clinical practice for patients with a
lower-limb amputation, (2) gait speed (mph) for prescribing moderate-intensity over-ground
and treadmill walking during the rehabilitation of patients with lower-limb amputations, and
(3) cadence (steps/minute), for evaluating and monitoring moderate-intensity physical
activity via step activity monitors, for inactive adults with a lower-limb amputation.

Investigators will provide the first objective data that looks at the additional energy
expenditure necessary for inactive adults with a lower-limb amputation who are using a
prosthesis to walk short-distances as compared to able-bodied adults; this data may be used
for the development of future prosthetic components that reduce energy expenditure.
Investigators will explore factors that may be linked to energy expenditure and physical
activity among adults with and without a lower-limb amputation.

Inclusion Criteria (all participants):

- Ages 18-60 years

- Able to read and speak English

- Saltin-Grimby Physical Activity Level of I or II

Inclusion Criteria (individuals with unilateral, transtibial amputations):

- Unilateral, transtibial (below-the-knee) amputation

- Currently wearing a prosthesis with use of an assistive device no greater than a cane

- Wearing prosthetic at least 8 hours per day and inside and outside the home: This
criteria will help to ensure that adults are beyond the initial weaning into a
prosthetic period and are prosthetic users rather than nonusers.

Inclusion Criteria (controls):

- Pain-free in the legs and low back regions

- Able to walk without an assistive device

Exclusion Criteria:

- Current infections or illnesses that would affect safe participation in the study

- Past medical history of significant cardiovascular disease (e.g. congestive heart
failure or previous heart attacks), significant neurological disease (e.g.
Parkinson's, Multiple Sclerosis) significant neurological event (e.g. stroke), or
major lung condition (e.g. Chronic obstructive pulmonary disease, emphysema)

- Uncontrolled high blood pressure

- Uncontrolled Diabetes Mellitus