Muscle Damage Affects Your Running Gait

Picture from Aspetar

I was away for my Kinesio Taping recertification for Instructors last week and had to exercise in a new environment. As the gym was much bigger and had equipment that I do not normally have access to, I chose to use mostly those. 

As a result I ended with muscle soreness almost all over. I went for a run a day after I came home and my running stride felt 'off.' Turns out I was not imagining it. That is how our bodies try to protect itself. So is that good or is that a problem?

Turns out it may be both (Markus et al, 2025). The muscle soreness indicate that adaptations are beginning. However, that soreness can also change our running form, increasing injury risk.

To assess how exercise induced muscle damage (EIMD in this study) or delayed onset of muscle soreness (DOMS) affects running biomechanics and recovery, researchers got their subjects to run downhill for 60 minutes. This was done on a treadmill at -10 percent gradient. The runners ran at 65 percent of their max heart rate.

The researchers tracked running gait changes, muscle soreness, blood markers for muscle damage and also did MRI scans of thigh muscles immediately post run, 24, and 48 hours after.

The runners took shorter steps 24 and up to 48 hours after that run, likely as a compensating mechanism since taking a smaller stride is the body's way of reducing impact when muscles are fatigued or damaged. Damaged muscles were verified (significantly elevated) using blood markers (creatine kinase and lactate dehydrogenase) and MRI scans showed thigh muscles damage. 

Take home message? If you just had a hard training session or especially a race, you have to expect some biomechanical changes for at least 48 hours after that if you still want to run. Since you have a reduced stride length, your pace will be slower and you will be running less eficiently. 

Anything else that will help? My personal experience suggests that performing reduced intensity and low volume exercise will increase blood flow to the affected muscles and often reduce pain. Pedaling at low resistance on a stationary bike is ideal as you don't have to worry about traffic (if you ride on the roads). An easy swim or just walking in waist or chest height water works well too.

 Wearing compression garments will help reduce it as well. These above mentioned strategies do have some support in the research.

Or better still, give yourself a few days of well earned rest (especially after a race) before going hard again. 

Reference

Markus I, Arutiunian A, Ohayon E et al (2025). Kinetics Of Recovery And Normalization Of Running Biomechanics Following Aerobic-Based Induced Muscle Damage In Recreational Male Runners. J Sci Med Sport. DOI: 10.1016/j.sams.2025.01.002

Kinesio Taping Instructor Recertification (CKTI) In Bangkok

I have not taught any Kinesio taping courses since 2019 in Malaysia, just before Covid-19 struck. In fact, the last course I taught in Singapore was in August 2018.

Kinesio Taping Association International needs our licence as a CKTI (certified Kinesio Taping Instructor) to be renewed  every 3 years to be able to teach again. There was an online recertification during the Covid years in 2021 which I attended, but due to the many rules in place I did not teach since then.

So I chose to come to the recertification in Bangkok since Alburqurque (held in October 2024) and Barcelona (January 2025) were much further away.

There was a memorial for Dr Kenso Kase (who passed away in August 2024) and Jim Wallis (December 2024) (a very senior instructor) at the event to honour them.

The course has definitely evolved. It is now called the Kinesio Foundations course (over 2 days) and we spent a lot of time (pictured below) over the last 2 days learning how to teach the new syllabus.

Sports Solutions will definitely be teaching the new Kinesio Foundations course. We will announce the dates when they are finalized. Stay tuned!

With Elisa Kase

Race Pace Versus Heart Rate Variability Guided Training

Picture taken from Flowly

A patient came in this week after he raced the Tokyo marathon last weekend. He was not happy as he started cramping in his hamstrings after 'only' 5 km.

I asked about how his training went. He told me he did 4 runs a week, all on a treadmill, mostly easy runs. His longest run was by time, 2:55 hrs (which he thought was equivalent to about 20 km).

He did all his runs with a heart rate monitor, training at "Zone 2" mostly and followed recovery metrics like heart rate variability *(HRV). Zone 2 training is low intensity exercise that involves training at 60-70 percent of maximum heart rate. He did not do any interval training nor any race pace training.

I discussed with him how he can do better since he will be running the Chicago marathon on October 12th this year. He really wants a improvement after his self described disastrous Tokyo race. I shared with him a study that tested 3 different approaches of training (Ranieri et al, 2025).The researchers split the runners into 3 different groups for 6 weeks. 

First, a heart rate based training group where training is prescribed by heart rate zones. Next a race pace training group in which training is prescribed running at percentages of race pace. Lastly a HRV guided training group. The HRV training group did training prescribed by heart rate zones but this was adjusted daily based on HRV readings. Hence their intensity was based on how well they recovered. 

All the runners did lab tests before and after the study. V02 max, running economy, ventilatory thresholds and other key endurance metrics. Participants were assessed by a 7 km time trial after the training period.

Results? Race pace training was the most reliable for improving race performance. Every single runner in that group went faster in the 7 km time trial with an average improvement of 3.8 percent. The runners also had gains in fat loss and maximal aerobic speed. The heart rate training group improved their ventilatory threshold readings but this did not lead to V02 max or time trial improvement. It did not deliver clear performance advantages over race pace training.

The HRV training group led to bigger physiological improvements. They had significant increases in ventilatory thresholds and V02 max, but this did not translate as well to race performance. Some participants also put on weight (fat mass) perhaps due to more frequent easy training days.

The authors concluded that race pace training had the least variablilty in response, meaning it worked reliably across runners. HRV based training showed individual differences, some saw gains, others did not. This is not surprising since HRV itself is highly variable.

I suggested to my patient that he needed to do some race pace training if he wanted to achieve his target timing. He can take his target finishing time and calculate how fast he needs to do his 1 km, 5 km or even 400m repeats. This teaches his body to gauge the pace he needs to run and not go too fast especially at the start. It will also prepare his body for the demands of race day.

I also suggested running more outdoors rather than solely indoors on a treadmill since the treadmill is softer and will not mimic the road conditions that he races on. Specificity is key. The gym environment is temperature controlled unlike outdoors. So if the race location is hotter and more humid then he will be less able to handle it.

Takeaway message? The best approach is not to train solely on a single approach. It is best to know when to use each approach. For example, you cannot train exclusively by race pace. The body will not be able to handle the load, one would likely get injured. 

Heart rate based training can definitely be used but should not be relied on exclusively too. It will improve physiological markers and your lab based testing (V02 max, lactate threshold), but may not result in faster race timings. 

HRV is a useful tool for monitoring stress and how well your body is recovering. Many professional athletes use it. However this study raises an important question of whether better physiological markers lead to better performance.

If you're looking for a fool proof way to inprove your race times, this study suggest that training at your race pace sould be a part of your training routine.

Reference

Ranieri LE, Casada A, Martin D et al (2025). Performance And Physiological Effects Of Race Paced-Based Versus Heart Rate Variability-Guided Training Prescription In Runners. Med Sci Sp Ex. DOI: 10.1249/MSS.0000000000003671

*Heart rate variability (HRV) is a measure of how much time passes between each heart beat. It is better to have a higher than lower number. It is physiological measurement that is used to understand how your body is coping with life and environmental changes. A low HRV may suggest that your body is not rested, less resilient  and may not handle changing situations. You can measure HRV with a smart watch, fitness tracker etc. 

Most People Will Never Sprint Again After ..

Sprinting behind our clinic

... they turn 30 for the rest of their lives.

Actually, I started doing a few 200 m sprints upslope along Warna Road once a week on Wednesday mornings about a month ago. This is usually after a 5 km warm up run. I have not done any sprints like this for a long, long time.

From Twitter (or now known as X)

Coincidently, I saw this 2 days ago (above) on Twitter (or X) and the title caught my eye. 95 percent of men and women will never sprint again by the time they reach 30 years of age. 

Do you think there's any truth to that claim? 

How's my running form?

Perhaps I should address why I started sprinting again after so many years? I felt my runs were stagnating. I only run twice a week now and though I entertain no dreams of competing, I long for the moments when I feel like it is 'effortless' to run. I also want to avoid sarcopenia.

I was never a high mileage runner previously. In the past when I was still competing, track intervals really helped me improve. So I thought it was a good time to restart some sprint work.

You can definitely improve performance by swapping distance for speed (Jin et al, 2025). In the quoted study, the researchers split well trained runners into 2 groups. These runners had an average VO2 max of 67 mL/kg/min and personal best of 14:38 mins for their 5k time. 

One group did sprint interval training (SIT). They did 10x30 seconds all-out sprints with 3.5 minutes rest twice a week for 6 weeks. The traditional training group continued running long distance twice a week.

Both groups also kept up their regular endurance base training (40-60 minute runs) 4 times a week other than the above sessions.

You can probably guess the results. After 6 weeks, the SIT group outperformed the traditional group in all endurance metrics. Their time to run exhaustion (which is a key indicator of endurance) was better.

They had a 5 seconds improvement in a 3000m time trial versus no change in the traditional training group. The SIT group also had faster 100 m and 400 m times, suggesting better speed and neuromuscular efficiency.

Surprisingly, there was only slight V02 max improvement in the SIT group even though running economy improved moderately. This shows that the SIT group became more efficient runners.

Now you know that sprint intervals are not just for sprinters. This study proves that endurance runners can gain real benefits when they add speedwork 1-2 times a week. 

You definitely don't have to follow this protocol in the quoted study. I started with just faster striding upslope before even attempting to sprint. Definitely not all out sprinting. I clocked about 50 seconds each rep when I first started and it's gone down to 40 seconds during my last rep 2 days ago.

All of us should sprint from time to time to recruit muscles that we don't normally use. I would also suggest jumping as high as you can too to build your explosive power. But not both at the same time. I do the jumps on my weight training days.

For those who still race, sprint training will definitely help improve performance without adding volume. You can improve your running efficiency while also improving your kick should you need to pass other runners at the last part of the race.

Reference

Jin K, Cai M, Zhang Y et al (2025). Effects Of 6-Week Sprint Interval Training Compared To Traditional Training On The Running Performance Of Distance Runners: A Randomized Controlled Trial. Front Physio. 16: 1536287. DOI: 10.3389/fphys.2025.1536287

If You Want Buns Of Steel ....

Ok I admit, that was a heading to get you to read this post. But seriously, I had a patient who was referred to our clinic by a GP across the road.  He hurt his groin while doing Brazilian jiu-jitsu 2 months ago and had not gotten better. He said his previous physiotherapist just got him to do clam shell exercises and it did not help at all. 

Want to know the best exercise for packing the biggest punch for the gluteal area? Let me share the results of the following study by Collings et al (2023).

Their study compared and ranked gluteal muscle forces in 8 hip focused exercises performed without and with external resistance, i.e. dumbbells or loaded barbell.

This 8 hip focused exercises in the study were single leg (S/L) squat, S/L Romanian deadlift (RDL), split squat, S/L hip thrust, banded side step, hip hike, side plank and side lying leg raise. The exercises were performed with and without weights for 12 reps max (RM)  and measured by electromyography (EMG). 

Analysis of muscle forces were limited to gluteus maximus (pictured above), medius and minimus (below). The results show that varying demands were placed on the individual gluteal muscles. Peak gluteal muscle forces significantly increased when all exercises were performed with weights compared with body weight alone. 

R gluteus medius and minimus

This is the first study to investigate a wide range of hip focused exercises that also includes isometric hip and hip abduction exercises. Clam shell exercises which you already know from my earlier  blog post is not great at activating gluteus medius and was not even included in this study. The S/L RDL and side plank  produced the highest peak gluteus medius and minimus muscle forces. 

Side plank

This is what I found most interesting. I was surprised that this variation of the side plank (pictured above) really targeted the gluteus medius and minimus too. It will be a good choice for physiotherapists to teach their patients this since no equipment is needed. Patients can easily do it at home or during on field/ court training.

Single leg RDL

We already know that the S/L RDL (pictured above) is good for  hamstrings strengthening. Done with weights, the S/L RDL activated high gluteus minimus force (100 percent observed) while gluteus maximus (98 percent) and gluteus medius (84 percent). S/L RDL is the go to exercise if you need to target all 3 gluteal muscles simultaneously along with the hamstrings.

To sum up, for the gluteus maximus, the split squat, S/L RDL and S/L hip thrust are the exercises that you want to do if that is what you want to train. The S/L RDL and side plank  produced the highest peak gluteus medius and minimus muscle forces. Those who are injured may start by doing the lower tier exercises and/ or reduce load (pictured above). You may want to remember this if your goal is to prevent injury, as part of rehabilitation or for performance.

Reference

Collings TJ, Bourne MN, Barrett RS et al (2023). Gluteal Muscle Forces During Hip-Focused Injury Prevention And Rehabilitation Exercises. Med Sci Sp Ex. 55(4): 650-660. DOI: 10.1249/MSS.0000000000003091

Bow Legged Or Knocked Knees? Or Normal?

Different knee shapes

Visual inspection of lower limb alignment is common standard practice for us in our clinics (and elsewhere I am sure) when a patient comes in with ankle, knee, hip and low back pain.

You would think that as a trained health professional, we would be able to see if a person has normal, bow legs (varus) or knocked knees (valgus) quite easily. If it was an extreme valgus or varus it would be fairly easy to differentiate. What if you saw the following pictures below?

Varus or valgus?

How about this? Confused?

Hence I was rather surprised when a published study (Nguyen et al, 2022) found that visual inspection of lower limb alignment is not valid nor reliable when compared to the gold standard of whole leg radiography (WLR).

The study involved 50 patients who underwent a WLR and a standardized digital photograph of the lower limbs (pictured below). The patient's feet were placed 10 cm apart and in 10 degrees of external rotation with knees in full extension and both arms alongside the body. Pictures were taken from knee height, 2 meters away from the patient. 

WLR and digital photograph

There were 4 assessors who rated the digital photograph twice. Two are orthopaedic surgeons with 10 and 5 years experience respectively. The remaining two were an orthopaedic resident and a researcher. They were unaware of the patients' hip knee angle (HKA).

Knees were rated with severe valgus (>5 degrees), moderate valgus (2-5 degrees), neutral, moderate varus (2-5 degrees) and severe varus (>5 degrees).

Ready for the results? The percentage of incorrect visual leg assessments ranged between 46-75 percent. Now that's high! The errors were lowest in patients with moderate valgus alignment (knock knees) and highest when the patient presented with a severe varus deformity (bow legs). See the picture below of a patient I saw recently. How can the error be highest when it is bow legged? Isn't that fairly obvious?

Surely this varus is obvious

There were patients with a neutral leg alignment but were assessed to be pathological in 50.7 percent of cases. I am concerned about this since the wrong diagnosis of normal presentation as pathological/ dysfunctional may potentially cause the patient to opt for surgical intervention. This will lead to increased health care cost for patients and insurers.

Interestingly, there were no significant differences between the accuracy of more experienced verus less experienced assessors.You would think that the ability to assess alignment would improve with practice through one's working life.

The results also show that there were gender influences. Women do present an increased risk for incorrect readings due to the difference in the angle of the thigh bone between men and women.

The authors concluded that visual assessment of lower limb alignment does not provide clinically relevant information. Physical examinations and X-ray assessments are advised.

Limitations for this study? My biggest gripe was that visual assessments were done on 2-dimensional (2D) digital photographs instead of in person assessment. It is definitely easier (and more accurate) to visually assess a patient than to look at a digital photograph. Only 1 assessor measured the HKA on the WLRs, so there is no comparison for inter-assessor reliability.

Hopefully our surgeons here in Singapore are better are visually assessing patients. They should also do whole leg x-rays and in clinic assessments. Make sure yours does.

We see many of these cases. Come see us in our clinics if you have any pain or discomfort. While we cannot alter the shape of your knees, we can definitely reduce or take away the symptoms.

Reference

Nguyen HC, Egmond N, De Visser HM et al (2022). Visual Inspection For Lower Limb Malalignment Diagnosis Is Unreliable. Cartilage. 13(4): 59-65. DOI: 10.1177/19476035221113952

Should You Strength Train On Unstable Surfaces?

On the BOSU ball

A patient come to our clinic this week injured after lifting weights on an unstable surface. The studio he went to had them do chest presses and flys with a glute bridge on a BOSU ball (knees bent, buttocks up and feet resting on BOSU ball). 

Indo board

I often use the BOSU ball, wobble board and/or  Indoboard (much later on - see end of article) when my patients require proprioceptive training to prep them before they return to sport. Also for those if they have lots of metalwork (pictured below) in the ankle after a fracture. I find that challenging my patients on unstable surfaces may enable them to rehab faster compared to stable surfaces when it is safe to do so.

Check out all the metal work in the leg

Other than working on their balance and proprioception (joint position sense), I get them to step on and off, lunge sideways, forward, backwards and sideways so they will be ready when the terrain that they are on are cambered or cobblestones (especially overseas).

However, I never use them while doing strength training. Turns out there is some research supporting that. I came across the following article to investigate if there are benefits or cross over effects of strength training on an unstable surface.

The following study evaluated subjects undergoing stable and unstable resistance training for muscle power. The subjects were randomly assigned into 2 groups. Each group performed resistance exercises under stable or unstable conditions 3 times a week for 8 weeks. 

Before and after 4 and 8 weeks of the training program, the subjects underwent squats and chest presses on either a stable surface or BOSU/ Swiss ball with increasing weights of up to 85 percent 1RM (rep max). 

There were significant improvements of mean power during chest presses on a Swiss ball at weights up to 60.7 percent 1RM after 4 and 8 weeks of raining on an unstable surface. Mean power also increased significantly during squats on a BOSU ball at weights up to 48.1 percent for 1RM after 4 weeks but not after 8 weeks of training on an unstable surface.

There were no significant changes in mean power during bench presses and squats on a stable surface after the same training. We do know from previous studies (Zemkova et al, 2014) that lower pre training values of power during resistance exercises on unstable surfaces are expected when compared to stable surfaces, especially at higher weights.

The researchers concluded that there is no cross over effect while weight training on unstable surfaces. Training has to be specific, if you want to get really strong and increase your 1RM max, you do not train on unstable surfaces since you cannot lift as heavy compared to on a stable surface.

Now you know, so you do not get hurt while trying something different that your gym suggests you do.

References

Zemkova E, Jelen M, Cepkova A et al (2021).There Is No Cross Effect Of Unstable Resistance Training On Power Produced During Stable Conditions. Appl Sci. 11(8): 3401. DOI: 10.3390/app11083401

Zemkova E, Jelen M, Kovacikva Z et al (2014). Weight Lifted And Countermovement Potentiation Of Power In The Concentric Phase Of Unstable And Traditional Resistance Exercises. J Appl Biomech 30: 213-220. DOI:10.1123/jab.2012-0229.

How's that for balance?