Can a Fitness Tracker Benefit the Lifter?

Today’s units are still better suited toward aerobic activity

In a society driven to fight the aging process using exercise, nutrition, information and data, fitness trackers satisfy the needs of many fitness enthusiasts. Since they exploded on the consumer market in the early 2000s, technology has continued to advance such that these devices can now calculate, store, and analyze a massive amount of information. Having evolved from the simplicity of tracking steps, heart rate, and calories burned, new devices can analyze sleep patterns and even claim to track alternative activities beyond cardio. Before you buy one, let’s review the pros and cons.

Generally, two types of trackers are on the market. Traditional models utilize a chest strap with a monitoring device that captures your heart rate during activity to calculate calories burned. Newer models, made to look like stylish accessories, can be worn on the wrist and track your heart rate through photoplethysmography (PPG). With PPG, a sensor shines directly on the skin and monitors changes in blood volume using LEDs. With this data, heart rate is determined on the theory that blood flow is inversely related to the amount of light reflected. These devices then plug a user’s heart rate and demographic information (e.g., age, weight, gender) into a formula to provide output data such as calories burned.

WHAT SCIENCE SAYS

Predominately, fitness trackers are marketed and used for cardiovascular activities such as walking and running. Here, studies have found their accuracy to be hit or miss.

One study found wrist-based trackers to accurately measure heart rate during a treadmill protocol, with error percentages ranging from 3.3 to 6.2 percent.¹ On the other hand, another study found much larger error percentages—from 9.3 to 23.5 percent—when it tested various devices.² That can overestimate an additional 250 calories burned in a 60-minute cardio session, an error that can easily lead to frustration as body composition goals aren’t being met.

BEYOND CARDIO

As a MUSCLE INSIDER reader (i.e., a serious weight lifter or someone looking to change your physique), you’re likely indifferent to fitness tracker outputs. Counting calories burned in your training session probably doesn’t matter as much as setting a new PR or building capped delts. But for those of you who are striving for weight loss and/or cardiorespiratory fitness and are tech savvy, such a device may fit your needs.

Such monitors are fairly useless during weight training because it’s vastly different from cardio, from a heart-rate and metabolism standpoint. The number of muscle fibres activated during training is much lower than in cardio, yielding either a lower heart rate output overall or more sporadic spikes because of the start/stop nature of the activity. During training, the increase in heart rate is caused by intrathoracic pressure rather than oxygen uptake—something these devices aren’t built to measure.

That changes if you follow a circuit-style workout; using plyometrics and body-weight exercises, fitness trackers may be more reliable. These sessions are much more cardiovascular-focused, allowing a tracker to gather the data it was created to capture.

For those just starting their fitness journey, a fitness tracker may help keep you accountable and consistent, which is most of the battle. Many people love the data they can collect about themselves, and with some apps you can even share your data. In these cases, trackers may be of great assistance as they can show progress, consistency, and general lifestyle habits.

REFERENCES

1. Stahl SE, An HS, Dinkel DM, Noble JM, Lee JM. How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough? BMJ Open Sport Exerc. Med. 2016 Apr 25;2(1):e000106.

2. Lee JM, Kim Y, Welk GJ. Validity of consumer-based physical activity monitors. Med Sci Sports Exerc. 2014 Sep;46(9):1840-8.