Designing, coding and validating sport science apps

Designing, coding and validating
#SportScience apps
Dr. Carlos Balsalobre-Fernández (@cbalsalobre)
Autonomous University of Madrid

Number of apps downloaded from the Appstore

Most popular
categories

Number of consumers of ﬁtness apps in the UK

ACSM’s list of ﬁtness trends for 2016

How many are scientiﬁcally validated…?

Fitbit Charge HR case
Users reported values dangerously low (i.e., 92bpm instead of 162)

How to make a validation study
Step #1: Check correlation with gold standard
vs

Step #2: Look for systematic bias
• Different approaches:
• T-Test for independent
measures
• Comparison with the
identity line
• Bland-Altman plots with
regression analysis of
the residuals
• …
Mean difference
p<0.05

Step #3: Reliability analysis
• Different approaches:
• Inter-session
• Intra-session
Intraclass Correlation Coefﬁcient
Cronbach’s alpha
Coefﬁcient of variation
Test-retest reliability

How an app is made
Programming LANGUAGES

How an iOS app is made
XCode and the Swift programming language
Xcode Swift

The very basic stuff: Storyboard

The very basic stuff: Variables
var jumpHeight: Int = 40
var flightTime: Double = takeOff - contact
var userName: String = textField.text!
var hasImproved: Bool = false

The very basic stuff: If-else statements
if jumpHeightPre <= jumpHeightPost {
result = "You have increased your
performance!"
} else {
result = "You still have work to do"
}

The very basic stuff
LIVE DEMO

Where to learn more?

Some validated apps
My Jump

Some validated apps
My Jump
• 100 jumps measured
simultaneously with My Jump
(120fps) and a Kistler force
platform
• r = 0.995
• Same reliability than the force
platform (ICC>0.97)
• 1.2cm mean diff with FP (smaller
in iPhone 6/6s)
• F-V proﬁle integration
• Just a bit cheaper than FP (5.99
vs 10000€)

Some validated apps
PUSH Band

Some validated apps
PUSH Band
• 3-axis accelerometer&gyroscope
• Measures velocity integrating
acceleration
• 150back squat reps measured
simultaneously with PUSH and a LT
• r = 0.91
• Equal intrasession reliability
(ICC>0.97)
• Systematic bias (peak -0.07m/s)
• Really practical iOS&Android app
• 260 vs 2600€

Some validated apps
My Sprint

Some validated apps
My Sprint
• By Pedro Jiménez-Reyes
• 72 sprints measured
simultaneously with My Sprint
(iPhone6), radar and
photocells
• r = 0.996
• Very high validity and reliability
• F0,V0, Pmax, effectiveness of
force application calculation
• 9.99 vs 4000€

Some validated apps
RUNMATIC

Some validated apps
RUNMATIC
• Measure running mechanics:
• Leg asymmetry, leg stiffness,
vertical oscillation, force, ground
contact time, ﬂight time & stride
frequency (using Morin et al. 2005)
• Validated with the Optojump Next
• r = 0.99
• Same reliability than the infrared
system (almost identical CV and α,
i.e.)
• 0.0038s mean difference between
2 observers (1 frame!)
0,2
0,2
0,2
0,3
0,3
0,2 0,2 0,2 0,3 0,3
R² = 0,9747

Some validated apps
RUNMATIC
• AVAILABLE TODAY for
iOS
• More info @Runmatic_
• 3.99 vs 3000€

Some validated apps
LIVE DEMO

The Future of #SportScience Apps
(you know, in my opinion)

The Future of #SportScience Apps
(you know, in my opinion)
• One device to rule them all
• Something you would wear even if
it won’t measure anything
• Most smartwatches has GPS, HR on
the wrist, accelerometers,
gryoscope…
• Future versions could include
sweating rate, blood pressure or
oxygen saturation sensors among
other variables
• With validated apps, a smartwatch
could be all you need

QUESTIONS?

1. 100% current iPhones have high-
speed cameras. Android below 1%
2. I know my apps will work on all
current iPhones. Can’t say the same
for Android
3. For same app on iPhone & Android,
iPhone version much more proﬁtable
4. Android apps are SUPER-EASY to
hack. iOS much more difﬁcult
5. Overall, it won’t worth the resources
and effort needed for independent
developers like me
>18000 different
Android phones
3 iPhones

But if you want it in Android it’s up to you!
All equations are published

Designing, coding and validating sport science apps

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