The Effect of Fatigue on the Forward-Step-Down Test

The purpose of this study is to investigate the effects that a volitional maximal
cardiovascular exertion test (the Bruce Treadmill Protocol) has on performance of the
Forward-Step-Down (FSD) test, and to investigate how performance on the FSD test changes at
multiple time points following the fatigue test.

Our hypotheses for this study are as follows:

- Null (H0): Participants will not demonstrate a change in score on the FSD test after
performance of the Bruce test at any time point.

- Alternate (H1): Participants will demonstrate a change in score on the FSD test after
performance of the Bruce test at one or multiple of the repeated measurements.

The FSD test has been shown to correlate with movement quality. Deficits in strength and
flexibility that result in movement impairments are associated with scores on the test
delineating "moderate" movement quality. Fatigue may play a role in increased injury risk,
with fatigued participants in numerous studies showing compromised movement patterns that
increase risk of injury. At this time, many of the screening tools used to determine the
impact of fatigue on a player's ability to continue to play/practice involved dynamic or
explosive movements, and rely on indicators such as femoral internal rotation or hip
adduction angles at initial contact to grade movement patterns. These biomechanical
indicators may be difficult for non-professional personnel to observe, limiting their use
outside a clinic. There is currently no research on the role of the FSD test in assessing for
changes in movement pattern that result from fatigue.

The literature currently acknowledges that fatigue results in altered movement patterns.
Several studies have investigated the impact that fatigue has on performing challenging
movements, such as plyometric drop jumps, cutting, jumping and running, and landing. However,
with higher level assessments such as these, there is an increased risk for injury if
performed while fatigued. Therefore, a lower level test, such as the FSD test, would be ideal
as a safe and effective screening tool to look at the impact of fatigue stimulus (game play)
on a person's movement quality. As stated above, the FSD test has been validated as a measure
of movement quality, with acceptable interrater reliability. In addition, poor movement
quality during the FSD test has been shown to correlate with several impairments such as hip
abductor strength and poor flexibility. Existing literature discusses the impact of the hip
abductors on knee position and risk for knee injury. Therefore, a functional test that
assesses not only movement quality but identifies possible causes of poor movement would be
ideal for preventing injury. Research has shown difference in postural balance following
aerobic fatigue depending on the time since fatigue, with poor performance immediately
following but improved performance 10 minutes after the fatigue stimulus was stopped.
Therefore, this study will examine the FSD test at one, five, and ten minutes following the
cardiovascular fatigue protocol in order to discern performance differences in movement
quality related to time/recovery. These differences may be important because if the FSD test
can be used as a screening tool to examine a person's fatigue level, it is important to also
know the appropriate time to use the test in order to get accurate results.

In this study, the Bruce test is used to achieve cardiovascular fatigue. Clinically it is a
"VO2max" (maximum volume of oxygen consumption) prediction test and is intended to continue
to the point of failure (maximum test). In a true VO2max test, the participant performs the
cardiovascular test until respiratory spirometry measures a plateau of the VO2, or oxygen
consumption, between two workloads. This is indicative of that participant's maximum
cardiovascular physiological limits. During a true VO2max test, respiratory gases are
analyzed as well as heart rate, blood pressure, and sometimes blood lactate samples are
obtained. Together these values determine the success in reaching a true VO2max test,
demonstrate cardiovascular fatigue, and ensure safety of the participant. Often, this point
is not reached in untrained or unhealthy individuals.

Performing a true VO2max test is more expensive and time-consuming for the participant than
performing a maximal or submaximal graded exercise test. Therefore, the Bruce protocol uses
mathematical derivation to predict VO2max from the participant's performance on the Bruce. To
estimate an accurate prediction of the VO2max and ensure cardiovascular fatigue, the target
heart rate is often set at within 10 bpm of the age-predicted maximum heart rate when using a
lower error formula such as the Tanaka formula. Therefore, in this study participants'
age-predicted maximum heart rate will be calculated using the formula derived by Tanaka with
an acceptable variability of within 10 bpm at the maximum heart rate measured during the
Bruce. The Tanaka formula is accurate for a population of healthy men and women. In this
study, "healthy" is defined as being in the "low risk" category for exercise as stated by the
American College of Sports Medicine, and is one of the inclusion criteria for this study.

- Prior to performing the testing, participants will be consented and screened for
inclusion and exclusion criteria at the end of an exercise physiology class during the
summer 2018 semester. This will occur before the students begin their exercise testing
labs in which the Bruce protocol is performed. Following consenting, participants will
proceed to the testing during the four-week data collection period during the summer
2018 semester.

- Each participant will perform the pre-and post-testing in the same day. The pre-fatigue
FSD test occurs just prior to the fatigue (Bruce) protocol, and the post-testing will
occur at one, five, and ten minutes after completion of the fatigue protocol. Initial
resting heart rate will be measured, as will heart rate at 0, 30, and 60 seconds
following completion of the Bruce to ensure appropriate heart rate responses to exercise
for a healthy young adult as per the inclusion criteria of participants being "low risk"
for adverse events during vigorous exercise.

- The expected duration to obtain all necessary participants is up to 4 weeks.

- The estimated time for the researches to perform the primary analysis is 3 months

- The estimated time to prepare the manuscript for publication is 1 year.

This study will be a repeated-measures design, with all participants undergoing both pre- and
post-fatigue FSD test assessments. Two orthopaedic specialist physical therapists will
perform the FSD assessments. The investigators will review scoring guidelines per the Park
article, and will practice scoring the test prior to data collection to ensure good
interrater reliability. Scores on the FSD test from each assessor will be averaged after data
collection and prior to data analysis, with each assessor blinded to the other's score prior
to averaging the scores. Participants will be healthy physical therapy students. Fatigue will
be induced via the Bruce protocol used in assessment of maximum cardiovascular capacity. The
treadmill used is an HP Cosmos Quasar (HP Cosmos, Germany). The heart rate monitors used are
Polar monitors (Polar Electro Inc, Bethpage, NY)

The FSD test grades the participant on movement quality during a repeated step down from a 20
cm step. The weight bearing leg will be the dominant leg (the leg the participant would use
to kick a ball) as used in the Park et al experiment. The FSD test consists of five repeated
movements of the forward step down, with one score given for the whole set of five
repetitions. For each set of five movements, the rater observes and produces one score for
that set of five movements. For data analysis, the investigators will use the average of each
score for each FSD test. For example, on the pre-test for a participant, if one investigator
scored the pre-test FSD a 2/6, and the second investigator scored the pre-test a 1/6, the
"averaged" score for the participant's pre-test is a 1.5/6. This same procedure would be
repeated for the three post-test FSD tests.

The Bruce protocol is self-limited with participants stopping at maximal exertion. Maximal
exertion will be defined as within 10 bpm of the participants predicted maximum heartrate as
calculated by the formula "208-(0.7 x age)" derived by Tanaka from a population of healthy
men and women. The within 10 bpm heart rate cutoff has been used as a benchmark of achieving
maximal exertion in a maximal exercise test based off the calculated maximum heart rate using
the Tanaka formula. The participants' Borg Rating of Perceived Exertion (RPE) will also be
recorded as part of the Bruce protocol; however, since the participants know they will have
to perform the FSD test following the Bruce protocol, the investigators will use heart rate
instead of RPE as a metric for exertion due to its more objective nature and to avoid a
possible threat to validity of the fatigue protocol. During the Bruce protocol, treadmill
speed and incline are increased every three minutes until the subject volitionally stops the
test at maximal exertion. Heart rate and RPE are monitored each minute during the Bruce
protocol, with assessment of blood pressure prior and following the treadmill test as part of
the Exercise Physiology class.

Inclusion Criteria:

- Participants will be recruited from current physical therapy students in the class of
2020 who are enrolled in PHTH 7565. During the consent process, the participants will
be screened using the American College of Sports Medicine's guidelines for safe
participation in vigorous exercise. By meeting the ACSM criteria, the participant is
considered low risk for adverse events while participating in vigorous activity.
Finally, in order for the student to participate, they must achieve within 10 bpm of
their predicted maximum heart rate, as calculated by the Tanaka formula as stated
above.

Exclusion Criteria:

- 3.2 Exclusion criteria are pre-existing cardiovascular conditions or diseases that
prevent participation in a maximal effort test without physician clearance per the
ACSM guidelines. Participants who do not reach their calculated target heart rate by
the end of the Bruce protocol will be withdrawn from the study and will not complete
post-fatigue testing.