Early changes in HRV relate to eventual fitness changes in collegiate soccer players

Numerous studies have shown that increases in fitness (e.g., VO2max, MAS, Yo-Yo, etc.) are associated with increased cardiac-parasympathetic activity among healthy, athletic and clinical populations. This is one of the reasons why aerobic exercise is considered to be cardio-protective, due to enhanced resting vagal-modulation.

However, there is considerable inter-individual variation in how a given individual responds to an exercise program. Following a standardized endurance training program, some individuals will show significant improvements in aerobic fitness while others will show only small improvements. Some may even regress. Why this occurs is likely due to a variety of potential variables including genetic factors, appropriateness of training stimulus and life style factors (i.e., sufficient recovery, sleep quality, nutrition, stress, etc.). Given the association between fitness changes and HRV changes, monitoring HRV throughout training may be useful in evaluating individual adaptation to a training program.

In our latest study (in press with JSCR), we wanted to determine if changes in HRV mid-way through a training program related to eventual changes in intermittent running performance in a collegiate female soccer team. It would be useful for coaches to be able to identify athletes who may not be coping well with training earlier on rather than waiting until post-testing to realize some athletes didn’t improve much. Coaches can then investigate the potential cause (i.e., fatigue, insufficient sleep, etc.) and intervene accordingly with modifications to training load or life style factors to get athletes back on track.

Before and after a 5-week conditioning program, we tested the team’s intermittent running capacity with the Yo-Yo IRT1. The conditioning program was designed based on the individuals max aerobic speed (MAS) adapted from Dan Baker’s MAS guide (link). Below is a screen shot of the conditioning program (unofficial).

MAS prog. Flatt

During week 1 and week 3, the athletes recorded their resting HRV each morning after waking with their smartphone using the ithlete HRV application which we validated previously (link). The weekly mean and weekly coefficient of variation (CV) for HRV and HR values were calculated. Change variables from week 1 to week 3 of HRV and HR (mean and CV) were correlated with the changes in Yo-Yo IRT1 performance from week 0 to week 5.

We found a very large correlation between the change in HRV CV at week 3 and Yo-Yo IRT1 changes at week 5 (r = -0.74). A large correlation was also found between the change in HRV mean and Yo-Yo IRT1 (r = 0.50). The HR measures showed only moderate correlations with the eventual changes in fitness.

Based on these results, it appears that monitoring HRV throughout training may be useful for evaluating how individual athletes are adapting to training. Specifically, we’re looking for two possible trend changes:

  1. A decrease in day-to-day fluctuation in HRV scores (i.e., decreased HRV CV)
  2. An increase in the weekly mean

Athletes demonstrating the opposite (increased CV and/or decreased weekly mean) may require a little closer attention from coaching personnel  to ensure that the training load is appropriate or that the athlete’s are taking care of the non-training factors that can be effecting their recovery.

Another novel finding of this study was that ultra-short HRV recordings (~1 min) derived from a smartphone app used by the athletes provided meaningful training status information. This indicates that HRV monitoring can be much more affordable and convenient than traditional approaches (i.e., longer recording periods with more expensive HRV tools).

I have plans for a much more elaborate post in the near future on the HRV CV. I’ll cover previous research, post some data and discuss how to interpret changes in the CV with appropriate context.

Link to current study: Evaluating individual training adaptation with Smartphone-derived heart rate variability in a collegiate female soccer team.

3 Month HRV and Wellness trends of two D1 Athletes

Below are the HRV trends of two NCAA D1 athletes from a team we’ve been working with over a 3 month period of virtually the same training schedule.

  • The vertical gray bars represent average perceived wellness (9 point scale)
  • The dotted horizontal black line is daily HRV
  • The thin black horizontal line is the 7-day rolling average
  • The dashed parallel horizontal lines represent the smallest worthwhile change (SWC = 0.5xCV)
  • HRV and wellness was acquired daily by the athletes with the ithlete finger sensor in the seated position.

Interestingly, these two athletes have very similar responses. About 3 weeks into the trend was a very intense training camp that was held out of state before Christmas. One athlete appears to experience more fatigue than the other with nearly the whole week below the SWC and a more pronounced decrease in wellness. HRV and wellness for both athletes improve over Christmas break. Following Christmas there is an intense 2-week training period followed by a reduction in training load. Both athletes frequently fall below the SWC here. Athlete A oscillates up and down while Athlete B remains below the SWC for nearly an entire week along with a decrease in wellness (middle of the trends). Both athletes trend upward after the intense training period and remain steady throughout the last half of the trend.

Athlete A

Athlete B

What makes things interesting is when athletes do not respond as expected. This is when the monitoring becomes invaluable as training intervention becomes extremely important.

HRV Monitoring Podcast Episode

About a month ago I had  the pleasure of being interviewed on the Quantified Body Podcast. In the interview we touch on a variety of topics including:

  • HRV basics
  • HRV recording methodology (duration, position, etc.)
  • Smart Phone Apps
  • Data analysis and interpretation
  • Practical Applications
  • Monitoring athletes
  • Current research projects
  • Misconceptions and common errors
  • Future directions
  • Etc. 

You can listen to the podcast from the Quantified Body website here.

There is a list of the names and resources mentioned within the episode on the Quantified Body web page. 

Your feedback is welcome.


Individual HRV Responses In Professional Soccer Players During A Competitive Season

In a team setting environment, athletes are often exposed to similar training loads during practices, training and competition. Monitoring of only the external training load provides coaches with an incomplete picture of how individual athletes may be responding and adapting to the training schedule. Two athletes can in fact respond entirely differently to the same program. A recently published case study by Bara-Filho et al. (2013) demonstrates how HRV, when measured periodically throughout training, can help distinguish these individual differences in professional soccer players exposed to the same training schedule. The following is a brief summary and review of this case study.

Materials and Methods

Subject 1 was a 26 year old Mid-Fielder with 7 years of professional playing experience. Subject 2 was a 19 year old Right Back with only 1 year of professional playing experience.

Over a 3 week period during a competitive season, both subjects participated in training that consisted of small-sided games, simulated matches, strength training, sprint training, and low-intensity aerobic recovery work. Training took place 1-2 times per day, 5 day’s/week culminating in a competition on the 6th day and rest on the 7th. Both subjects were starters in the 3 matches that occurred over the observation period.

HRV was measured on 5 occasions throughout the 3 week period on each Saturday and Monday morning (excluding the last Monday). This allowed for HRV indices to be evaluated both after the weekly training load was accumulated (Saturday) and after recovery (Monday). This is precisely the protocol that I discussed in a recent post entitled Making HRV More Practical for Athletes: Measurement Frequency.

HRV data was collected in the morning with a Polar RS800 watch while the athletes rested in a supine position.


Total weekly TRIMP values were similar in both athletes. After the first measurement (M1) Subject 1 showed an increasing trend in several HRV values (RMSSD, HF, SDNN, SD1) indicating good adaptation to training and quality recovery from competition. Subject 2 showed a progressively decreasing trend in these same HRV values indicating an accumulation of fatigue and insufficient recovery.


The authors suggest that subject 2, who saw a decreasing trend in his HRV values, may have been experiencing stressors unrelated to sport that may have contributed to his insufficient recovery. Though subjective measure (questionnaires) were not included, the physical training coach reported that athlete 2 would inform him that he was experiencing disturbed sleep, fatigue during training, and poor recovery.

A lower level of playing experience in subject 2 was reported as another possible explanation for his descending HRV trend. The psychological stressors and anxiety experienced by this younger athlete may have also contributed.

The authors briefly discuss the limitations of a supine measurement only when using HRV to monitor training load in athletes. Essentially, individuals with low resting heart rates appear to be subject to “parasympathetic saturation” in the supine position, possibly skewing the data. Therefore, including measurement performed in the standing position may serve as a resolution to this issue. I discussed this topic in a previous post entitled Supine vs. Standing HRV Measurement.

Finally, the authors conclude that HRV values were useful in monitoring the effects of a competitive training schedule in athletes as these values appear to be sensitive to individual characteristics as well as stress and recovery. A stable or increasing HRV trend appears to be favorable as it indicates quality recovery and adaptation to training. In contrast, a decreasing trend in HRV indicates higher stress and impaired recovery which may necessitate recovery interventions and reductions in training load.


Bara-Filho, M.G., et al. (2013) Heart rate variability and soccer training: a case study. Motriz: rev. educ. fis. 19(1): 171-77. Free Full-Text

Updates, free monitoring spread sheet with questionnaire & an HRV video.

1) I was recently contacted by a researcher based out of Australia and asked to beta test his new HRV app. I’ve had the app and hardware for a few days now and it has some really cool features. In a future post I will give my thoughts and review of the app (with the creator’s permission).

2) Last week T-Nation published the “HRV Roundtable Discussion” article. The roundtable contributors were; Craig Weller, James Heathers, Mike T. Nelson, Patrick Ward, Joel Jamieson, Simon Wegerif, Jonathan Pope, Dave Tenney and myself.

This discussion took place earlier in the year and ended up being over 20 pages in length! Many of the pages were adjusted to 8 or 10 point font to reduce the number of pages. A ton of great thoughts and ideas were shared by some very intelligent people. I learned a lot from being a part of this discussion and am very grateful for having been asked to contribute. Craig organized and edited the entire discussion. I can only imagine how long and arduous of a process that was. You can read the discussion HERE.

3) For any strength coaches who are interested in utilizing HRV analysis with your teams, you’ll be interested to know that iThlete has a team app in production. This app will make monitoring RHR, HRV, training load, etc. of each member of your team very easy. I will see if I can get a post up in the near future with some screen shots and more details. I’m very excited for this!

4) Training has been going extremely well for me since moving back to Canada. I can now deadlift without any pain or discomfort in my lower back. I’m considering finally entering a meet again this winter. If I decide to do this I’d like to document my meet prep programming, HRV trends, RPE’s, etc. both for myself (to see what worked and what didn’t) and for my readers because they are training nerds like me.

5) Download a FREE monitoring survey and excel spreadsheet here. This can be very useful to keep track of of your players throughout the season.

6) I came across a very informative video lecture last month that explains the various HRV analysis methods (Time domain, Frequency domain, Poincare plot). The video provides demonstrations of how to use the free Kubios software to analyze data. If you’re interested in learning more about the more technical aspects of HRV analysis, check it out.

Strength and Conditioning vid’s from across the NCAA (Football, Baseball, Softball, Soccer etc)

Here are some college strength and conditioning video’s from across the NCAA that you might enjoy. I’ll try and post some new video’s once a week from now on.

Ole Miss Football


Maryland Football


South Carolina Football


Notre Dame Football


Dayton Football


Notre Dame Hockey


North Texas Football


Florida State Football


Southern Miss Women’s Softball


Merrimack Baseball


Oklahoma State S&C Facility


Army Football

Happy Easter!

Welcome to hrvtraining

My name is Andrew Flatt and I hold a Master’s Degree in Exercise Science and am a CSCS with the NSCA. I currently reside in Montgomery, AL where I am completing several research projects pertaining to HRV and exercise at Auburn University at Montgomery. I recently worked as an assistant strength and conditioning coach at Cal U in PA. I was the strength and conditioning coach at a private high school in Ontario for 3 years prior to pursing a Master’s degree. I have an extensive athletic background including hockey, rugby and collegiate football. I now compete in raw powerlifting and was the 2010 Canadian National Champion (amateur). I am interested in all aspects of strength and conditioning however my research interest pertains to Heart Rate Variability and its application to monitoring the training of athletes.

With this blog I intend to;

  • share anecdotes, research and anything else I can regarding heart rate variability (HRV) as I feel it is a technology that will soon be used by the majority of trainers, strength coaches and individuals to better monitor and manipulate their  training loads.
  • discuss any other aspect of strength and conditioning that happens to be on my mind.
  • make an effort to provide training updates with  HRV scores and relevant information to allow interested readers to see how HRV is effected on a day to day basis in a strength athlete from training and other daily stressors
  •  include book and product reviews as I like to read and buy stuff related to strength and conditioning.
  • share video’s and resources that I feel readers of this blog will find useful