Image source: Fitbit.

Fitbit (NYSE:FIT) is slipping these days. Shares of the top dog in wearable tech began the new trading week 24% lower than they were at their summertime peak less than a month ago. Fitbit stock has now moved lower for seven straight market sessions, surrendering 11.3% of its value along the way.

The latest setback is a Cleveland Clinic study debunking the efficacy of fitness bracelets in general to gauge the wearer's heart rate correctly. Folks don Fitbit devices primarily to monitor daily activity, but a welcome perk is that the wristbands also have a pulse on your pulse. 

Cleveland Clinic physicians concluded that chest-worn monitors that work similar to an electrocardiogram are more effective than wrist-worn trackers. The findings shouldn't come as much of a surprise. Fitbit and rival bracelets use optical sensors to gauge blood flowing through veins. It's not ideal. There are shortcomings to using optical sensors as opposed to chest-worn electrodes, and they're also measuring blood flow that is farther from the heart. 

It's still hard to see why this became a big deal last week. Hardcore athletes don't mind strapping on chest-worn heart monitors when they're taking on extreme physical challenges, but will mainstream consumers be interested in the cumbersome data trackers to monitor daily activities? No one is expecting hospital-quality readings from a simple fashion accessory. 

Fitbit starts to backpedal

The Cleveland Clinic report isn't the only study that's been giving bulls a reason to cool on the stock. A report out of Singapore earlier this month came to the conclusion that most study participants abandon fitness trackers over time. The study -- funded by Singapore's ministry of health and published in the Lancet Diabetes & Endocrinology trade journal -- also found that even the participants who were offered financial incentives to lead more active lives didn't generate substantial improvement in weight loss or blood pressure. 

That particular study, with the 800 participants wearing Fitbit Zip devices, may be more problematic than the Cleveland Clinic report since it hits the mass market. If wearing a Fitbit and moving around more isn't a game changer, why invest in one at all?

The good news is that most physicians will agree that an active lifestyle is healthier than a dormant one. Fitbit also countered with studies showing how at least two companies that decided to offer employees Fitbit trackers saw substantial declines in their health coverage costs. 

Things may not seem very encouraging at the moment. Fitbit seemed to be rallying through the summer. The 21% gain for the stock during the third quarter was its first full quarterly gain since going public last year. However, now the stock is trading 12% lower early into the fourth quarter. Fitbit has some ground to make up, and making sure that it wins the war of public opinion is huge as we head into the important holiday shopping season.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.