Using Submaximal Fitness Tests in Team Sports: A Practical, Evidence-Informed Approach
- Jo Clubb
- 20 minutes ago
- 6 min read
This post explores how submaximal heart rate responses can be used to monitor aerobic fitness in team sport athletes - without adding testing burden - and how a new Firstbeat Sports feature supports this approach.
In team sport environments, the logistical and physiological demands of maximal fitness testing often outweigh the benefits, particularly in-season. Yet, our athletes' aerobic fitness remains of interest so a more pragmatic approach is required.
Submaximal fitness testing offers a practical, low-burden alternative. And now, thanks to a new feature in Firstbeat Sports, practitioners can automate and visualise results from this approach, making it easier than ever to monitor aerobic fitness with minimal disruption.
This post explains the rationale for using heart rate during submaximal exercise to assess fitness, highlights recent research on its validity and implementation, and explores how the new Firstbeat feature supports practitioners in applied settings.
Submaximal Fitness Testing: Rationale and Application
Quantifying athletes’ responses to training stimuli is a fundamental aspect of performance preparation in team sports. While laboratory-based or field-based maximal aerobic tests remain the gold standard for assessing aerobic capacity, their repeated use during the competitive season is often impractical. Fatigue, fixture congestion, and resource or equipment limitations can make maximal testing unfeasible, particularly for large squads.
This has led to a growing interest in alternative methods that can assess aerobic-oriented training effects with lower burden on athletes and staff. Submaximal Fitness Tests (SMFT) provide one such solution. These tests involve low-to-moderate intensity exercise protocols that can be embedded within routine training, typically during the warm-up, without inducing additional fatigue or disrupting the session plan.
The core principle underpinning submaximal testing is that as an athlete’s aerobic fitness improves, their cardiovascular response to a fixed external workload becomes more efficient. In practical terms, this is most often assessed via heart rate. Exercise heart rate (HRex) reflects the internal physiological cost of a standardised external load and is considered a valid proxy for aerobic capacity during steady-state exercise.
This form of “invisible monitoring” enables the integration of fitness surveillance into the training process itself, providing meaningful insights with minimal disruption. It is not about testing without athlete knowledge, but rather about minimising the burden and logistical costs typically associated with fitness assessments.
What Does the Research Say?
Recent systematic reviews have supported the growing application of SMFT in team sports. Tzlil Shushan and colleagues published two comprehensive reviews that catalogued over 100 submaximal protocols and proposed a useful classification framework. Their taxonomy categorised SMFT based on two key variables:
Exercise regimen: continuous vs. intermittent
Intensity progression: fixed, incremental, or variable
From these dimensions, they categorised five distinct protocol types used across various sports. They also explored the variety of outcomes used with the test and two heart rate–derived indices were among the most common:
Heart Rate Exercise (HRex) – the average heart rate during the final 30–60 seconds of the test
Heart Rate Recovery (HRR) – the rate at which HR declines after exercise cessation, typically the first minute immediately after the test
Both variables are physiologically meaningful. HRex is strongly associated with oxygen uptake during steady-state exercise and is widely used as a surrogate for aerobic capacity. HRR, on the other hand, reflects autonomic nervous system recovery (specifically parasympathetic system reactivation), with an increase representing a positive effect.
A Recommended Submaximal Fitness Test Protocol
Based on their reviews, Shushan et al. (2023) proposed a continuous running protocol over flat terrain, ideally minimising change of direction to reduce neuromuscular demand. The target speed should fall between 10–14 km/h (depending on the population) to elicit a heart rate corresponding to approximately 75–85% of maximum.
The protocol duration should be 3–4 minutes, with HRex taken from the final 60 seconds. If possible, HRR should be recorded in the 60 seconds following the end of the test.
To improve test-retest reliability, consistency is critical. Practitioners should aim to control for time of day, surface type, environmental conditions, and athlete preparation (although admittedly this is difficult in the team sport environment!).
HR traces should also be visually inspected to check for artefacts, dropout, or signal drift that could compromise interpretation. Historically this has been quite burdensome on practitioners but as we'll see below, Firstbeat Sports new testing feature makes this simple and instant.
Automating the Analysis: Firstbeat Sports Fitness Testing
While submaximal tests themselves are simple to administer, collecting and analysing the data can be time-consuming. Without automation, practitioners must manually define time windows, calculate heart rate averages, compare to historical data, and exclude poor-quality samples.
That’s where the new Firstbeat Sports Fitness Testing feature adds real value. As you can see in the video demonstration further above, this tool allows you to:
Define your fixed protocol
Choose whether to include HRR
Select athletes and apply start times individually or in bulk
Automatically extract HRex and HRR values
Compare results to previous tests
Track individual change over time using Z scores or percent change
Visualise and clean the data with heart rate trace overlays
The result is a repeatable workflow that turns raw data into interpretable insights, helping you integrate submaximal testing into your monitoring system without increasing administrative burden. Included as part of a holistic, multivariate athlete load management system, these act as simple alerts or red flags to explore further.
What the Data Tells Us
In general, a downward trend in HRex over time in response to a standardised SMFT suggests improved exercise economy. The athlete is completing the same stimulus at a lower cardiovascular cost - consistent with aerobic adaptation. Conversely, elevated HRex values may indicate a negative response (e.g., detraining) due to central adaptations.
Like all monitoring tools, these interpretations benefit from context. One-off spikes should not prompt overreaction, but sustained increases - especially if accompanied by changes in performance or subjective wellness - may warrant further attention. Submaximal heart rate responses are not diagnostic. But when paired with other data and athlete dialogue, they offer a low-cost, high-frequency snapshot of aerobic status.
Summary
Submaximal fitness testing offers an efficient and evidence-informed way to monitor a simple proxy for aerobic fitness in team sports, particularly when logistical constraints limit traditional testing. By embedding a low-intensity, standardised protocol into the training process, practitioners can monitor key heart rate metrics such as HRex and HRR without adding fatigue, cost, or disruption.
And with the new Firstbeat Sports Fitness Testing feature, this process is now simpler, more automated, and more actionable than ever. Whether you're monitoring pre-season progression, return-to-play readiness, or in-season trends, this approach supports smarter, lower-burden fitness surveillance.
FAQs on Submaximal Fitness Testing
What is submaximal fitness testing (SMFT)?
Submaximal fitness testing refers to the use of low-to-moderate intensity exercise protocols—typically embedded within routine training—to assess an athlete’s physiological response to a standardised workload. These tests avoid the fatigue associated with maximal assessments and provide insight into aerobic-oriented training effects.
How does heart rate reflect aerobic fitness?
During steady-state, submaximal exercise, heart rate is closely related to oxygen uptake. A lower heart rate response to a fixed workload (i.e. reduced HRex) is typically indicative of improved aerobic efficiency or cardiovascular adaptation. Similarly, faster heart rate recovery post-exercise (HRR) suggests enhanced parasympathetic reactivation and fitness.
Is submaximal testing as accurate as maximal testing?
Submaximal tests do not directly measure VO₂max or other maximal physiological capacities. However, they offer a valid and reliable surrogate—especially when repeated consistently over time. The trade-off is improved feasibility, frequency, and athlete compliance, making them particularly valuable for longitudinal monitoring in applied settings.
What are the limitations of SMFT?
The main limitation is sensitivity to confounding variables. Factors such as hydration status, illness, environmental temperature, and sleep can affect heart rate responses independently of fitness. For that reason, interpretation must consider context, and test conditions should be as consistent as possible across sessions.
How does the Firstbeat Sports fitness testing feature help with submaximal fitness testing?
The new feature automates the extraction, calculation, and visualisation of submaximal fitness test data. It enables practitioners to define a standardised protocol, monitor heart rate responses over time, and detect meaningful trends, without adding manual data processing workload.
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