IEEE Systems, Man and Cybernetics Magazine - January 2021 - 5

apparatuses and applications used for this purpose. Our
review and discussion are intended to help entrepreneurs
and engineers improve their products to better meet
users' needs and aid researchers in identifying potential
new areas.

artificial agents or real humans to coach users, socialization approaches that support users in communicating
and competing with each other, and gamification and
exergaming approaches intended to promote healthy
lifestyles and fitness activities. Afterward, we explore
the interaction interfaces used in these systems as a subsection of motivational advances.
The latter part of this article lists the challenges and
opportunities that we identified, which can help the
research and the engineering community move forward in
this promising direction, with an
eye toward further advancements.

Indoor Physical Activities
Due to the rapid growth of urbanization, many populations
participate in sports and training in indoor environments,
chiefly gyms. Physical activity fosters well-being and
reduces the risk of various chronic
diseases. As cases of diabetes [1]
and cardiovascular disease [2] are
In particular, there
Existing Systems
on the rise worldwide, the demand
for gyms has continually increased.
are two types of
The U.S. fitness industry is estimatData Collection Tools
equipment used in
ed at a US$30 billion value and has
Most technological advances have
been growing at an annual rate of
focused on data collection. Here,
the gym that apply
3-4% over the past 10 years [3].
we provide a brief overview of the
to weight training:
This demand creates a large martypes and characteristics of senfree weights and
ket for digital apparatuses and
sors used for data collection.
applications that assist users in
fixed resistance.
fitness tracking, coaching, and
Sensor Classification
motivation [4].
The core of data collection devicIndoor activities are usually
es is their sensors, and existing
classified into two types: aerobic and anaerobic exercise.
activity tracking systems can be broadly classified into
Aerobic exercise, often known as cardio, is suitable for
two categories: proximity [7] and mobile/wearable [8]
users who want to lose weight and improve or maintain
sensors. However, there is no clear border between the
their cardiopulmonary condition. Modern gyms and
categories, and it is possible for a single sensor to
homes use equipment such as treadmills, stair mills, rowbelong to both [7]. At the time of writing this article,
ing machines, and spin bikes, which support a variety of
wearable sensors are being commercialized and widely
aerobic exercise. Anaerobic exercise is primarily accomavailable in the consumer market. On the other hand,
plished with weight training activities, which contribute
proximity sensors are in their infancy and not yet wideto training specific muscles. The U.S. Department of
ly in use; we believe that they will soon be commercialHealth and Human Services recommends incorporating
ized by fitness ser vice providers. However, unlike
strength training exercise for all major muscle groups into
wearables, which are personalized, they should be
a fitness routine at least twice per week [3], indicating
shared by a specific group of users. Because wearable
that it is as important as aerobic exercise.
devices are heterogeneous, for example, the recent Wear
In particular, there are two types of equipment used
operating system improves battery use compared to its
in the gym that apply to weight training: free weights
old version [9], and because proximity sensors are not
and fixed resistance. Despite the wide variety of technolyet widely in use, we refrain from providing a quantitaogies related to indoor physical activities, most existing
tive comparison in this research.
technologies are focused on fitness trackers and aerobic
exercise [5], while anaerobic exercise, such as weight
Proximity Sensors
training, is underrepresented [6]. Therefore, we believe it
A proximity (environmental) sensor is fixed and does not
is crucial to outline the latest advancements related to
move with the user [see Figure 1(a)]. In contrast, a mobile
indoor fitness and list the potential areas for further
sensor is wearable and will move with its user [see Figimprovement to contribute to the research and engineerure 1(b)]. An example of a proximity sensor is a pulse
ing communities' work in this area. To have a better
sensor (used to measure heart rate), which is mounted
understanding of the challenges and opportunities in
on the handle of a device-for example, an elliptical-to
this area, the first part of this article introduces existing
read a user's pulse rate. This information will be dissystems. First, we describe data collection tools and
played on the device's ambient screen, which may also
methods, including applications and sensors. Next, we
show some basic coaching advice, such as a recommendpresent different approaches to motivate users to pered maximum heart rate based on the age the user inputs,
form and stay committed to physical exercise. This
or a suggestion of when to decrease the intensity of the
includes a brief review of the coaching tools that employ
exercise. Heart rate sensors and ambient displays have

Ja nu a r y 2021

IEEE SYSTEMS, MAN, & CYBERNETICS MAGAZINE

IEEE Systems, Man and Cybernetics Magazine - January 2021

Table of Contents for the Digital Edition of IEEE Systems, Man and Cybernetics Magazine - January 2021